Publications by authors named "Nguyen Thu Ha"

73 Publications

Blood Lead Levels and Associated Sociodemographic Factors among Children Aged 3 to 14 Years Living near Zinc and Lead Mines in Two Provinces in Vietnam.

Biomed Res Int 2021 6;2021:5597867. Epub 2021 Jul 6.

Faculty of Public Health, Haiphong University of Medicine and Pharmacy, Vietnam.

Lead poisoning in children is a major public health concern worldwide, especially in developing countries. We conducted a cross-sectional study on 403 children aged from 3 to 14 years living nearly zinc-lead mining areas in two provinces in Vietnam (Bac Kan and Thai Nguyen) from 06/2016 to 10/2016 to identify risk factors for lead contamination. . The proportion of children with blood lead levels (BLLs) ≥ 10 g/dL was 80.51% in Bac Kan and 50% in Thai Nguyen; the mean blood lead level for children was 14.41 ± 9.42 g/dL. In linear regression analyses, the body mass index was negatively associated with elevated BLLs with = -0.404, < 0.05 (95% CI: -0.801, -0.006). In multivariable regression analysis, several risk factors were associated with lead contamination including male sex (aOR = 2.44, 95% CI: 1.13-5.24, = 0.02), play areas in Bac Kan (aOR = 2.3 (1.02-5.17), = 0.04), proximity of children's home of less than 2 kilometers from the mine (aOR = 2.90 (1.54-5.44), = 0.001), and inattentive symptoms in Thai Nguyen (aOR = 7.85, 95% CI 3.49-17.69, = 0.001). Environmental factors, including lead concentrations in the soil and ambient air samples in both locations, are many times higher than Vietnamese standards.
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http://dx.doi.org/10.1155/2021/5597867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8277519PMC
July 2021

Looking Through the COVID-19 Window of Opportunity: Future Scenarios Arising From the COVID-19 Pandemic Across Five Case Study Sites.

Front Psychol 2021 7;12:635686. Epub 2021 Jul 7.

School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom.

The COVID-19 pandemic has caused (and continues to cause) severe disruption in global and local economies and has forced countries, societies, and individuals to adapt quickly to the unprecedented and unpredictable situations. Despite the obvious negative consequences of the pandemic, many have called for efforts to identify transformative opportunities for sustainable development throughout this disorderly time. In the present paper, we explore such potential opportunities in the context of an interdisciplinary, international research project, which is focusing on sustainable marine management in biosphere reserves and marine parks in Southeast Asia. During a virtual workshop conducted as part of the GCRF (Government's Global Challenges Research Fund) Blue Communities Project, future scenarios were developed depicting the potential effects of the COVID-19 pandemic on five case study sites. All of these sites are in areas of internationally recognized outstanding ecological value (Taka Bonerate Kepulauan-Selayar Biosphere Reserve, Indonesia; Tun Mustapha Park, Sabah, Malaysia; Palawan Biosphere Reserve, Philippines; North Devon Biosphere Reserve, United Kingdom; Cu Lao Cham-Hoi An Biosphere Reserve, Vietnam). At the macro-level, economies, governance structures, and societal norms are undergoing big changes. At the micro-level, the livelihoods, lifestyles, and backyards of local residents have to adapt. Collaboratively, we explored how COVID-19 posed challenges in our five case study sites, but we also focused on the potential COVID-19-related windows of opportunity for future sustainable development. Opportunities could be identified in all three pillars of sustainable development: the environment, the society, and the economy. Although remarkable similarities can be found across all five sites, we conclude that there cannot be a "one-size-fits-all" solution to turn the tide toward achieving sustainable development. Just as before the pandemic, sustainable development starts with engaging with and understanding local environments, challenges, and situations; building on local knowledge; and developing tailor-made solutions for the communities .
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http://dx.doi.org/10.3389/fpsyg.2021.635686DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8293277PMC
July 2021

Tailoring chemical compositions of biodegradable mesoporous organosilica nanoparticles for controlled slow release of chemotherapeutic drug.

Mater Sci Eng C Mater Biol Appl 2021 Aug 4;127:112232. Epub 2021 Jun 4.

Center for Innovative Materials and Architectures, Ho Chi Minh City, Viet Nam; Vietnam National University-Ho Chi Minh City, Ho Chi Minh City, Viet Nam. Electronic address:

Biodegradable periodic mesoporous organosilica nanoparticles (B-PMO) are an outstanding nanocarrier due to their biodegradability and high drug load capacities. The present study describes a synthesis of a phenylene-containing tetrasulfide based B-PMO, named P4S. The incorporation of aromatic phenylene groups into the framework creates a strong interaction between nanoparticles (NPs) with aromatic rings in the cordycepin molecules. This results in the low release profile under various conditions. In addition, the replacement of this linker slowed the degradation of nanoparticles. The physicochemical properties of the nanoparticles are evaluated and compared with a biodegradable ethane-containing tetrasulfide based PMO and a non-degradable MCM-41. The biodegradability of P4S is also demonstrated in a reducing environment and the 100 nm spherical nanoparticles completely decomposed within 14 days. The porous structure of P4S has a high loading of hydrophilic cordycepin (approximately 731.52 mg g) with a slow releasing speed. The release rates of P4S NPs are significantly lower than other materials, such as liposomes, gelatin nanoparticles, and photo-crosslinked hyaluronic acid methacrylate hydrogels, in the same solution. This specific release behavior could guarantee drug therapeutic effects with minimum side-effects and optimized drug dosages. Most importantly, according to the in vitro cytotoxicity study, cordycepin-loaded P4S NPs could retain the toxicity against liver cancer cell (HepG2) while suppressed the cytotoxicity against normal cells (BAEC).
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http://dx.doi.org/10.1016/j.msec.2021.112232DOI Listing
August 2021

Efficient Secretion and Recombinant Production of a Lactobacillal α-amylase in WCFS1: Analysis and Comparison of the Secretion Using Different Signal Peptides.

Front Microbiol 2021 14;12:689413. Epub 2021 Jun 14.

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Vienna, Austria.

Lactic acid bacteria (LAB) have been used as starter cultures and producers of enzymes, antimicrobial peptides or metabolites that contribute to the flavor, texture and safety of food products. , one of the best-studied LAB, is considered as safe and effective cell factory for food applications. In this study, our aim was to use as the producer for high levels of a food-grade lactobacillal α-amylase, which has potential applications in food, fermentation and feed industries. The native form of an α-amylase (AmyL) from S21, an amylolytic LAB isolated from Thai fermented rice noodles, was expressed in WCFS1 using the pSIP expression system. The secretion of the α-amylase was driven by the native signal peptides of the α-amylases from S21 (SP_AmyL) and NRRL B-4549 (SP_AmyA), as well as by three Sec-type signal peptides derived from WCFS1; Lp_2145, Lp_3050, and Lp_0373. Among the tested signal peptides, Lp_2145 appears to be the best signal peptide giving the highest total and extracellular enzymatic activities of α-amylase AmyL from S21, which were 13.1 and 8.1 kU/L of fermentation, respectively. These yields were significantly higher than the expression and secretion in WCFS1 using the native signal peptide SP_AmyL, resulting in 6.2- and 5.4-fold increase in total and extracellular activities of AmyL, respectively. In terms of secretion efficiency, Lp_0373 was observed as the most efficient signal peptide among non-cognate signal peptides for the secretion of AmyL. Real-time reverse-transcriptase quantitative PCR (RT-qPCR) was used to estimate the mRNA levels of α-amylase transcript in each recombinant strain. Relative quantification by RT-qPCR indicated that the strain with the Lp_2145 signal peptide-containing construct had the highest mRNA levels and that the exchange of the signal peptide led to a change in the transcript level of the target gene.
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http://dx.doi.org/10.3389/fmicb.2021.689413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8236982PMC
June 2021

Does National Colorectal Cancer Screening Program Represent Good Value for Money? Results from a Return-on-Investment Model in Vietnam.

Health Serv Insights 2021 24;14:11786329211017418. Epub 2021 May 24.

Hanoi University of Public Health, Hanoi, Vietnam.

To provide important evidence for the resource allocation process in Vietnam, this research was conducted to explore the return on investment (ROI) of the national colorectal cancer (CRC) screening program. A decision tree model was designed to estimate the cost and cost savings of a national screening program (ie, providing annual fecal occult blood test [FOBT], following with colonoscopy in case of FOBT positive for the medium-risk group over 50 years old) compared to no screening scenario. This was the first attempt in estimating the ROI of a public health program in Vietnam. Although there was a wide variation due to the uncertainty of the input parameters, especially regarding the coverage of the colorectal cancer screening program in the community, the calculated ROI rates in all different cases were positive, demonstrating that the national colorectal cancer screening program brought benefits to the investment. With a modest coverage of 30% of the population over the age of 50, the corresponding ROI value was 325.4% (95%UI: 321.0; 329.9). The results of this study could be used to advocate for the implementation of a national colorectal cancer screening program in terms of the monetary benefits of investing in the program.
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http://dx.doi.org/10.1177/11786329211017418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8150636PMC
May 2021

Effectiveness of Two Regimens for Colon Cleansing Using Polyethylene Glycol 4000: A Randomized Open Label Trial.

Indian Pediatr 2021 May 28. Epub 2021 May 28.

Hôpital Saint Vincent de Paul, Groupement des Hôpitaux de l'Institut Catholique de Lille (GHICL), Université Catholique de Lille, BD de Belfort, 59020 Lille Cedex, France.

Aim: To compare effectiveness, safety and tolerance of two colon cleansing regimens using polyethylene glycol 4000 (PEG) in children.

Methods: Prospective, randomized, open clinical trial carried out in 129 children, 3 to 18 years old undergoing colonoscopy. Patients were randomized into two groups, 64 children received PEG with electrolyte (50 mL/kg) and oral bisacodyl (PEG+B) group or 65 other children received PEG with electrolyte (70 mL/kg) and glycerol enema (PEG+G) group.

Results: Both regimens showed a good colon cleansing effectiveness with the percentage of successful cleansing being 93.8% for PEG+B regimen and 89.1% for PEG+G regimen (P=0.510). There was no statistically significant difference between the pre-regimen and post-regimen laboratory values. The rates of nausea (65.6% vs 31.3%; P<0.001) and bloating (50% vs 17.2%; P<0.001) of PEG+G group were significantly higher than that of PEG+B group.

Conclusion: Both regimens had good efficacy and safety for clon cleansing in children. The tolerance of PEG+B regimen was better.
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May 2021

Health Insurance Reimbursement to Hosptials in Vietnam: Policy Implementation Results and Challenges.

Health Serv Insights 2021 14;14:11786329211010126. Epub 2021 Apr 14.

Hanoi University of Public Health, Hanoi, Vietnam.

In Vietnam, social health insurance (SHI) benefit package has been defined in a more explicit approach with the introduction of a regulation on the list of conditional reimbursed and non-reimbursed medical services. This paper aims to analyze the implementation results of this regulation from an economical perspective as well as the implementation challenges. Mix-method approach was employed. The quantitative component was employed to understand the implementation results. Desk study and qualitative components (2 inteviews with key informants from Ministry of Health; 6 discussions with key informants from provincial Social Security Offices and Departments of Health in Hanoi, Ho Chi Minh City, Hue, Tuyen Quang, Thai Binh and Soc Trang provinces; the other 23 discussions and 31 interviews with key informants from 23 selected hospitals) was employed to summarize the implementation challenges. The regulation seems to not able to mitigate the reimbursement of high-technology and expensive services in higher-level providers. There is a sign of increasing out-of-pocket payments for those regulated services in higher-level providers. It has also posed greater influence on lower-level providers in terms of the proportion of reimbursement amount rather than to higher-level hospitals. Applying World Health Organization's 6 building blocks of health system to analyze the implementation challenges, we provide policymakers evidence to improve the regulation, as well as point out the relating health system weakness need to be strengthened.
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http://dx.doi.org/10.1177/11786329211010126DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8050760PMC
April 2021

Improving silymarin oral bioavailability using silica-installed redox nanoparticle to suppress inflammatory bowel disease.

J Control Release 2021 03 22;331:515-524. Epub 2020 Oct 22.

Department of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan; Master's School of Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan; Center for Research in Isotopes and Environmental Dynamics (CRiED), University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki, 305-8573, Japan. Electronic address:

Chronic inflammatory diseases such as inflammatory bowel diseases (IBD), which are strongly related to the overproduction of reactive oxygen species (ROS), have become more threatening to health. Silymarin is an active compound with the effect of expressing anti-inflammatory activity; however, it exhibits poor bioavailability due to the rapid metabolism and secretion, low permeability across the intestinal epithelial cells, and poor water solubility. In this study, we developed silica-containing redox nanoparticles (siRNP) with 50-60 nm in diameter to improve the bioavailability of silymarin by improving its uptake into the bloodstream and delivery to the targeted tissues of the colon. Silymarin-loaded siRNP ([email protected]) significantly increased the antioxidant capacity and anti-inflammatory efficacy in vitro by scavenging 2,2-diphenyl-1-picrylhydrazyl free radical and suppressing nitric oxide and pro-inflammatory cytokines as compared to the other treatments such as free silymarin, siRNP, and silymarin-loaded si-nRNP (the control nanoparticle without ROS scavenging property). Orally administered [email protected] significantly improved the bioavailability of silymarin and its retention in the colonic mucosa. The anti-inflammatory effects of [email protected] were also investigated in dextran sodium sulfate (DSS)-induced colitis in mice and it was observed that [email protected] treatment significantly improved the damage in the colonic mucosa of DSS colitis mice as compared to the other treatments. The results in this study indicate that [email protected] is a promising nanomedicine for enhancing the anti-inflammatory activity of silymarin and has a high potential for the treatment of IBD.
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http://dx.doi.org/10.1016/j.jconrel.2020.10.042DOI Listing
March 2021

A new cytotoxic compound from the leaves of Guillaumin.

Nat Prod Res 2021 Feb 22:1-9. Epub 2021 Feb 22.

Institute of Marine Biochemistry, Vietnam Academy of Science and Technology (VAST), Hanoi, Vietnam.

New propene derivative 1-(3,4-methylenedioxyphenyl)-2-(2-hydroxy-5-(3-hydroxypropyl)-3-methoxyphenyl)prop-2-en-1-one (), along with three known triterpenoids ursolic acid (), pomolic acid (), and maslinic acid () were isolated from the leaves of species. All structures were assigned by spectroscopic analysis. Compound showed potent cytotoxicity against four cancer cell lines (KB, HepG2, Lu, and MCF7) with the IC values of 3.19, 2.87, 2.33, and 2.44 µM, respectively.
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http://dx.doi.org/10.1080/14786419.2021.1887868DOI Listing
February 2021

Interdisciplinary Assessment of Hygiene Practices in Multiple Locations: Implications for COVID-19 Pandemic Preparedness in Vietnam.

Front Public Health 2020 26;8:589183. Epub 2021 Jan 26.

Department of Psychological Medicine, National University Hospital, Singapore, Singapore.

Due to the shared border with China, Vietnam faced risks from the COVID-19 pandemic at the early stages of the outbreak. Good hygiene practices were considered an effective prevention method, but there were only minimal data on the effectiveness of hygiene practices against the pandemic at the community level. Thus, this study aims to assess hygiene practices in society by using a community-based survey. A cross-sectional study using survey monkey was conducted from December 2019 to February 2020. The Snowball sampling technique was used to recruit participants and exploratory factor analysis was applied to scrutinize the construct validity of the measurement. We used the Tobit regression model to assess the association. Hygiene in a high-risk environment and hygiene in the social and educational environment were two main factors after applying the EFA method. Participants grade community sanitation quite low (around 6 out of 10). Furthermore, the mean score of hygiene practice at a local level in a high-risk environment was slightly low at 6.0. The score of sanitation in the Central region (5.3) was quite low compared to the North (5.8) and the South (6.2). The most high-risk environment was construction, industrial zone and food safety. Moreover, younger respondents were more likely to report poorer hygiene practices in high-risk environments (Coefficient = -1.67; 95% CI = -3.03; -0.32) and social and educational environment (Coefficient = -1.29; 95% CI = -2.54; -0.04). Our study gives an insight into pandemic preparedness at the grassroots level. The findings suggest the necessity of specific communication education for society to improve the compliance of hygiene practices to prevent the spreading of COVID-19.
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http://dx.doi.org/10.3389/fpubh.2020.589183DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7870988PMC
February 2021

Evaluating Training Need for Epidemic Control in Three Metropolitans: Implications for COVID-19 Preparedness in Vietnam.

Front Public Health 2020 5;8:589331. Epub 2020 Nov 5.

Department of Psychological Medicine, National University Hospital, Singapore, Singapore.

Upon the outbreak of the COVID-19 pandemic, countries worldwide face a critical shortage of human resources in the health sector. Medical students are a potential task force with the capability to support the stretched health sector. This study aims to evaluate their training need for epidemic control in order to employ them effectively. A cross-sectional study was conducted using a web-based survey from December 2019 to February 2020. There were 5,786 observations collected using the snowball sampling technique. Logistic regression was applied to identify factors associated with training participation in epidemic prevention and disaster prevention. Multiple Poisson regression model was constructed to examine factors associated with the number of times they participated in sanitation training and disaster prevention activities in the previous 12 months. Sanitation and health education communication activities had the highest proportion of participants, with 76.5 and 38.4%, followed by examining and treating diseases in the community (13.4%). Those who participated in community activities had a higher number of times to participate in epidemic sanitation training and be involved in disaster prevention. This study informed the need for training programs to prepare medical students for COVID-19 epidemic responses. The training curriculum should include both theoretical approaches and contextual approaches to achieve efficient epidemic control.
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http://dx.doi.org/10.3389/fpubh.2020.589331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7674483PMC
May 2021

Cell Wall Anchoring of a Bacterial Chitosanase in Using a Food-Grade Expression System and Two Versions of an LP TG Anchor.

Int J Mol Sci 2020 May 27;21(11). Epub 2020 May 27.

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190 Vienna, Austria.

Lactic acid bacteria (LAB) have attracted increasing interest recently as cell factories for the production of proteins as well as a carrier of proteins that are of interest for food and therapeutic applications. In this present study, we exploit a lactobacillal food-grade expression system derived from the pSIP expression vectors using the (alanine racemase) gene as the selection marker for the expression and cell-surface display of a chitosanase in using two truncated forms of a LP × TG anchor. CsnA, a chitosanase from 168 (ATCC23857), was fused to two different truncated forms (short-S and long-L anchors) of an LP × TG anchor derived from Lp_1229, a key-protein for mannose-specific adhesion in WCFS1. The expression and cell-surface display efficiency driven by the food-grade -based system were compared with those obtained from the based pSIP system in terms of enzyme activities and their localisation on cells. The localization of the protein on the bacterial cell surface was confirmed by flow cytometry and immunofluorescence microscopy. The highest enzymatic activity of CsnA-displaying cells was obtained from the strain carrying the -based expression plasmid with short cell wall anchor S. However, the attachment of chitosanase on cells via the long anchor L was shown to be more stable compared with the short anchor after several repeated reaction cycles. CsnA displayed on cells is catalytically active and can convert chitosan into chito-oligosaccharides, of which chitobiose and chitotriose are the main products.
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http://dx.doi.org/10.3390/ijms21113773DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312796PMC
May 2020

Coverage of Health Information by Different Sources in Communities: Implication for COVID-19 Epidemic Response.

Int J Environ Res Public Health 2020 05 20;17(10). Epub 2020 May 20.

Department of Psychological Medicine, National University Hospital, Singapore 119074, Singapore.

Health personnel and community workers are at the front line of the COVID-19 emergency response and need to be equipped with adequate knowledge related to epidemics for an effective response. This study aimed to identify the coverage of COVID-19 health information via different sources accessed by health workers and community workers in Vietnam. A cross-sectional study using a web-based survey was carried out from January to February 2020 in Vietnam. Respondent-driven sampling (RDS) was used for recruiting participants. We utilized the exploratory factor analysis (EFA) to examine the construct validity of the questionnaire. A higher percentage of participants knew about "Clinical and pathogen characteristics of COVID-19", compared to "Regulations and policies related to COVID-19". The percentage of participants accessing the information on "Guidelines and policies on prevention and control of COVID-19" was the lowest, especially among medical students. "Mass media and peer-educators" channels had a higher score of accessing COVID-19 information, compared to "Organizations/ agencies/ associations" sources. Participants consumed most of their COVID-19 information via "Internet, online newspapers, social networks". Our findings indicate an urgency to re-design training programs and communication activities for a more effective dissemination of information related to the COVID-19 epidemic or epidemics in general.
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http://dx.doi.org/10.3390/ijerph17103577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7277747PMC
May 2020

Co-production of gallic acid and a novel cell-associated tannase by a pigment-producing yeast, Sporidiobolus ruineniae A45.2.

Microb Cell Fact 2020 Apr 25;19(1):95. Epub 2020 Apr 25.

Food Biotechnology Laboratory, Faculty of Food Science and Technology, BOKU University of Natural Resources and Life Sciences, 1190, Vienna, Austria.

Background: Gallic acid has received a significant amount of interest for its biological properties. Thus, there have been recent attempts to apply this substance in various industries and in particular the feed industry. As opposed to yeasts, fungi and bacteria and their tannases have been well documented for their potential bioconversion and specifically for the biotransformation of tannic acid to gallic acid. In this research, Sporidiobolus ruineniae A45.2 is introduced as a newly pigment-producing and tannase-producing yeast that has gained great interest for its use as an additive in animal feed. However, there is a lack of information on the efficacy of gallic acid production from tannic acid and the relevant tannase properties. The objective of this research study is to optimize the medium composition and conditions for the co-production of gallic acid from tannic acid and tannase with a focus on developing an integrated production strategy for its application as a feed additive.

Results: Tannase produced by S. ruineniae A45.2 has been classified as a cell-associated tannase (CAT). Co-production of gallic acid obtained from tannic acid and CAT by S. ruineniae A45.2 was optimized using response surface methodology and then validated with the synthesis of 11.2 g/L gallic acid from 12.3 g/L tannic acid and the production of 31.1 mU/mL CAT after 48 h of cultivation in a 1-L stirred tank fermenter. Tannase was isolated from the cell wall, purified and characterized in comparison with its native form (CAT). The purified enzyme (PT) revealed the same range of pH and temperature optima (pH 7) as CAT but was distinctively less stable. Specifically, CAT was stable at up to 70 °C for 60 min, and active under its optimal conditions (40 °C) at up to 8 runs.

Conclusion: Co-production of gallic acid and CAT is considered an integrated and green production strategy. S. ruineniae biomass could be promoted as an alternative source of carotenoids and tannase. Thus, the biomass, in combination with gallic acid that was formed in the fermentation medium, could be directly used as a feed additive. On the other hand, gallic acid could be isolated and purified for food and pharmaceutical applications. This paper is the first of its kind to report that the CAT obtained from yeast can be resistant to high temperatures of up to 70 °C.
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http://dx.doi.org/10.1186/s12934-020-01353-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7183711PMC
April 2020

Structural Comparison of Different Galacto-oligosaccharide Mixtures Formed by β-Galactosidases from Lactic Acid Bacteria and Bifidobacteria.

J Agric Food Chem 2020 Apr 6;68(15):4437-4446. Epub 2020 Apr 6.

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190 Vienna, Austria.

The LacLM-type β-galactosidase from DSM 20075 expressed in both (β-gal) and (β-gal) was tested for their potential to form galacto-oligosaccharides (GOS) from lactose. The Lh-GOS mixture formed by β-galactosidase from , together with three GOS mixtures produced using β-galactosidases of both the LacLM and the LacZ type from other lactic acid bacteria, namely, (Lr-GOS), (Lb-GOS), and (St-GOS), as well as two GOS mixtures (Br-GOS1 and Br-GOS2) produced using β-galactosidases (β-gal I and β-gal II) from , was analyzed and structurally compared with commercial GOS mixtures analyzed in previous work (Vivinal GOS, GOS I, GOS III, and GOS V) using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), high-performance size-exclusion chromatography with a refractive index (RI) detector (HPSEC-RI), and one-dimensional H NMR spectroscopy. β-Galactosidases from lactic acid bacteria and displayed a preference to form β-(1→6)- and β-(1→3)-linked GOS. The GOS mixtures produced by these enzymes consisted of mainly DP2 and DP3 oligosaccharides, accounting for ∼90% of all GOS components. GOS mixtures obtained with β-galactosidases from lactic acid bacteria and were quite similar to the commercial GOS III mixture in terms of product spectrum and showed a broader product spectrum than the commercial GOS V mixture. These GOS mixtures also contained a number of GOS components that were absent in the commercial Vivinal GOS (V-GOS).
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http://dx.doi.org/10.1021/acs.jafc.9b08156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7168588PMC
April 2020

Sinking of microbial-associated microplastics in natural waters.

PLoS One 2020 3;15(2):e0228209. Epub 2020 Feb 3.

Laboratory for Advanced Environmental Engineering Research, School of Civil Engineering, The University of Sydney, Sydney, New South Wales, Australia.

Degraded plastic debris has been found in nearly all waters within and nearby urban developments as well as in the open oceans. Natural removal of suspended microplastics (MPs) by deposition is often limited by their excess buoyancy relative to water, but this can change with the attachment of biological matter. The extent to which the attached biological ballast affects MP dynamics is still not well characterised. Here, we experimentally demonstrate using a novel OMCEC (Optical Measurement of CEll colonisation) system that the biological fraction of MP aggregates has substantial control over their size, shape and, most importantly, their settling velocity. Polyurethane MP aggregates made of 80% biological ballast had an average size almost twice of those containing 5% biological ballast, and sank about two times slower. Based on our experiments, we introduce a settling velocity equation that accounts for different biological content as well as the irregular fractal structure of MP aggregates. This equation can capture the settling velocity of both virgin MPs and microbial-associated MP aggregates in our experiment with 7% error and can be used as a preliminary tool to estimate the vertical transport of MP aggregates made of different polymers and types of microbial ballast.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0228209PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6996825PMC
April 2020

Current research on single-entity electrochemistry for soft nanoparticle detection: Introduction to detection methods and applications.

Biosens Bioelectron 2020 Mar 27;151:111999. Epub 2019 Dec 27.

Department of Chemistry, The Research Institute of Natural Sciences, Sookmyung Women's University, Seoul, 04310, Republic of Korea. Electronic address:

In recent years, rapid progress in the field of single-entity electrochemistry (SEE) has opened a novel exploratory area in the field of analytical and electrochemistry. SEE is a method of studying the behavior of particles at the single particle level, which yields important information on the diffusion coefficient, individual particle size, size distribution, catalytic activity, collision frequency, and internal substances of the particles. Various types of particles have been studied through SEE. Among them, this review focuses on the results of analyzing soft particles (cells, proteins, viruses, liposomes, enzymes, vesicles, emulsion droplets, micelles, carbonaceous nanomaterials, and others). We introduce the various electrochemical techniques used in SEE and discuss important concepts and equations that must be known to apply SEE. We also introduce the results of recent research on several important soft particles. Finally, the potential applications in areas such as sensors, materials, catalysts, energy, and biomedicine, as well as the trends of related works are described. In the future, research on soft particle analysis using SEE is expected to increase rapidly, and this review is expected to be a valuable reference for researchers in the field.
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http://dx.doi.org/10.1016/j.bios.2019.111999DOI Listing
March 2020

Burden of injuries in Vietnam: emerging trends from a decade of economic achievement.

Inj Prev 2020 10 8;26(Supp 1):i75-i82. Epub 2020 Jan 8.

Faculty of Social Science, Behaviors and Health Education, Hanoi University of Public Health, Hanoi, Vietnam.

Background: Vietnam has been one of the fastest-growing world economies in the past decade. The burden of injuries can be affected by economic growth given the increased exposure to causes of injury as well as decreased morbidity and mortality of those that experience injury. It is of interest to evaluate the trends in injury burden that occurred alongside Vietnam's economic growth in the past decade.

Methods: Results from Global Burden of Disease 2017 were obtained and reviewed. Estimates of incidence, cause-specific mortality, years lived with disability, years of life lost, disability-adjusted life years were analysed and reported for 30 causes of injury in Vietnam from 2007 to 2017.

Results: Between 2007 and 2017, the age-standardised incidence rate of all injuries increased by 14.6% (11.5%-18.2%), while the age-standardised mortality rate decreased by 11.6% (3.0%-20.2%). Interpersonal violence experienced the largest increase in age-standardised incidence (28.3% (17.6%-40.1%)), while exposure to forces of nature had the largest decrease in age-standardised mortality (47.1% (37.9%-54.6%)). The five leading causes of injury in both 2007 and 2017 were road injuries, falls, exposure to mechanical forces, interpersonal violence and other unintentional injuries, all of which increased in incidence from 2007 to 2017. Injury burden varied markedly by age and sex.

Conclusions: The rapid expansions of economic growth in Vietnam as well as improvements in the Sociodemographic Index have occurred alongside dynamic patterns in injury burden. These results should be used to develop and implement prevention and treatment programme.
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http://dx.doi.org/10.1136/injuryprev-2019-043352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7571350PMC
October 2020

Identification, Classification and Screening for γ-Amino-butyric Acid Production in Lactic Acid Bacteria from Cambodian Fermented Foods.

Biomolecules 2019 11 22;9(12). Epub 2019 Nov 22.

Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences Vienna, Muthgasse 18, A-1190 Vienna, Austria.

Screening for various types of lactic acid bacteria (LAB) that form the biological agent γ-amino-butyric acid (GABA) is important to produce different kinds of GABA-containing fermented foods. So far, no GABA-producing LAB have been reported from Cambodian fermented foods. Most small-scale fermentations and even some industrial processes in this country still rely on indigenous LAB. The application of GABA-producing autochthonous starters would allow the production of Cambodian fermented foods with an additional nutritional value that meet the population's dietary habits and that are also more attractive for the international food market. Matrix-assisted laser desorption/ionizing time-of-flight mass spectrometry (MALDI-TOF MS) and partial 16S rDNA sequencing were used to identify 68 LAB isolates from Cambodian fermented foods. These isolates were classified and grouped with (GTG) rep-PCR, resulting in 50 strains. Subsequently, all strains were investigated for their ability to produce GABA by thin layer chromatography. GABA-positive strains were further analyzed by the GABase assay. Of the six GABA-positive LAB strains-one , two , and three strains-two strains produced high amounts of GABA (20.34 mM, 16.47 mM). These strains should be further investigated for their potential application as GABA-producing starter cultures in the food applications.
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http://dx.doi.org/10.3390/biom9120768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6995518PMC
November 2019

Ammonium tetrathiomolybdate enhances the antitumor effect of cisplatin via the suppression of ATPase copper transporting beta in head and neck squamous cell carcinoma.

Oncol Rep 2019 Dec 10;42(6):2611-2621. Epub 2019 Oct 10.

Department of Oral and Maxillofacial Surgery, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700‑8525, Japan.

Platinum‑based antitumor agents have been widely used to treat head and neck squamous cell carcinoma (HNSCC) and numerous other malignancies. Cisplatin is the most frequently used platinum‑based antitumor agent, however drug resistance and numerous undesirable side effects limit its clinical efficacy for cancer patients. Cancer cells discharge cisplatin into the extracellular space via copper transporters such as ATPase copper transporting beta (ATP7B) in order to escape from cisplatin‑induced cell death. In the present study, it was demonstrated for the first time that the copper chelator ammonium tetrathiomolybdate (TM) has several promising effects on cisplatin and HNSCC. First, TM suppressed the ATP7B expression in HNSCC cell lines in vitro, thereby enhancing the accumulation and apoptotic effect of cisplatin in the cancer cells. Next, it was revealed that TM enhanced the antitumor effect of cisplatin in HNSCC cell tumor progression in a mouse model of bone invasion, which is important since HNSCC cells frequently invade to facial bone. Finally, it was demonstrated that TM was able to overcome the cisplatin resistance of a human cancer cell line, A431, via ATP7B depression in vitro.
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http://dx.doi.org/10.3892/or.2019.7367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826331PMC
December 2019

Immobilization of β-Galactosidases on the Cell Surface Using the Peptidoglycan-Binding Motif LysM.

Catalysts 2019 May;9(5):443

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences, A-1190 Vienna, Austria.

Lysin motif (LysM) domains are found in many bacterial peptidoglycan hydrolases. They can bind non-covalently to peptidoglycan and have been employed to display heterologous proteins on the bacterial cell surface. In this study, we aimed to use a single LysM domain derived from a putative extracellular transglycosylase Lp_3014 of WCFS1 to display two different lactobacillal β-galactosidases, the heterodimeric LacLM-type from and the homodimeric LacZ-type from subsp. on the cell surface of different spp. The β-galactosidases were fused with the LysM domain and the fusion proteins, LysM-LacLMLreu and LysM-LacZLbul, were successfully expressed in and subsequently displayed on the cell surface of WCFS1. β-Galactosidase activities obtained for displaying cells were 179 and 1153 U per g dry cell weight, or the amounts of active surface-anchored β-galactosidase were 0.99 and 4.61 mg per g dry cell weight for LysM-LacLMLreu and LysM-LacZLbul, respectively. LysM-LacZLbul was also displayed on the cell surface of other spp. including subsp. and however is shown to be the best among spp. tested for surface display of fusion LysM-LacZLbul, both with respect to the immobilization yield as well as the amount of active surface-anchored enzyme. The immobilized fusion LysM-β-galactosidases are catalytically efficient and can be reused for several repeated rounds of lactose conversion. This approach, with the β-galactosidases being displayed on the cell surface of non-genetically modified food-grade organisms, shows potential for applications of these immobilized enzymes in the synthesis of prebiotic galacto-oligosaccharides.
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http://dx.doi.org/10.3390/catal9050443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6783300PMC
May 2019

Association of Human Leukocyte Antigen Haplotypes With End-Stage Renal Disease in Vietnamese Patients Prior to First Transplantation.

Transplant Proc 2019 Oct 28;51(8):2549-2554. Epub 2019 Aug 28.

Department of Nephrology and Transplantation, 108 Military Central Hospital, Hanoi, Vietnam.

Introduction: The prevalence of chronic kidney failure is significantly increasing in Vietnam, causing a burden for health care. This study assessed the relationship of HLA-A, -B, and -DRB1 alleles with end-stage renal disease (ESRD).

Method: A retrospective, cross-sectional study and a comparative study using secondary data analysis were conducted on 196 ESRD patients and 187 controls from 2009 to 2017. The patient and donor profiles were collected from medical records, including age, sex, etiology of renal failure, and HLA phenotypes. HLA-A*, -B*, and -DRB1* typing were done by polymerase chain reaction-sequence specific primers.

Result: The most frequent HLA alleles in Vietnamese patients with ESRD were HLA-A*02, -A*11, -B*15, -B*46, -DRB1*04, -DRB1*09, and -DRB1*12. The haplotypes HLA-A*0233 (odds ratio [OR] = 0.40, 95% CI: 0.15-0.98) had a negative association for ESRD. The haplotypes HLA-B*1515 (OR = 4.14, 95% CI: 1.52-11.26) and HLA-DRB1*1212 (OR = 2.01, 95% CI: 1.06-3.81) had a positive association for ESRD. The haplotypes HLA-B*1515 (OR = 4.69, 95% CI: 1.69-13.03) and -DRB1*1212 (OR = 2.15, 95% CI: 1.10-4.21) had a positive association for ESRD related to glomerulonephritis. The HLA-B*1557 (OR = 17.34, 95% CI: 2.70-11.49) had a positive association for ESRD related to hypertension.

Conclusion: The haplotypes of HLA class I and II had significant relationships with ESRD. The results of our study should be confirmed in further investigations.
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http://dx.doi.org/10.1016/j.transproceed.2019.03.067DOI Listing
October 2019

Expression of a leptospiral leucine-rich repeat protein using a food-grade vector in , as a strategy for vaccine delivery.

3 Biotech 2019 Sep 8;9(9):324. Epub 2019 Aug 8.

1Interdisciplinary Graduate Program in Genetic Engineering, Graduate School, Kasetsart University, Bangkok, Thailand.

In this study, a first food-grade mucosal vaccine against leptospirosis was developed without the use of antibiotic resistance gene. This expression system is based on a food-grade host/vector system of and a new vaccine candidate antigen, a leucine-rich repeat (LRR) protein of . The LRR of interest from serovar Sejroe is encoded by two overlapping genes and these genes were fused together by site-directed mutagenesis. The mutant gene thus obtained could be successfully expressed in this system as was shown by western blot analysis and liquid chromatography-mass spectrometry (LC-MS/MS) analysis. In addition, this analysis showed that the mutant LRR protein fused to a homologous signal peptide of could be exported to the cell surface as a result of the native LPXAG motif of the heterologous LRR protein, which presumably is responsible for anchoring the protein to the cell wall of This new strategy could be an essential tool for further studies of leptospirosis mucosal vaccine delivery.
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http://dx.doi.org/10.1007/s13205-019-1856-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6687796PMC
September 2019

Improving lipid production by strain development in microalgae: Strategies, challenges and perspectives.

Bioresour Technol 2019 Nov 2;292:121953. Epub 2019 Aug 2.

Department of Life Science, Research Institute for Natural Sciences, Hanyang University, Seoul, Republic of Korea. Electronic address:

Over the past decade, the number of original articles and reviews presenting microalgae as a promising feedstock for biodiesel has increased tremendously. Many improvements of microalgae have been achieved through selection and strain development for industrial applications. However, the large-scale production of lipids for commercialization is not yet realistic because the production is still much more expensive than that of agricultural products. This review summarizes recent research on the induction of lipid biosynthesis in microalgae and the various strategies of genetic and metabolic engineering for enhancing lipid production. Strain engineering targets are proposed based on these strategies. To address current limitations of strain engineering for lipid production, this review provides insights on recent engineering strategies based on molecular tools and methods, and also discusses further perspectives.
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http://dx.doi.org/10.1016/j.biortech.2019.121953DOI Listing
November 2019

Constitutive expression and cell-surface display of a bacterial β-mannanase in Lactobacillus plantarum.

Microb Cell Fact 2019 Apr 25;18(1):76. Epub 2019 Apr 25.

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences Vienna, Muthgasse 18, 1190, Vienna, Austria.

Background: Lactic acid bacteria (LAB) are important microorganisms in the food and beverage industry. Due to their food-grade status and probiotic characteristics, several LAB are considered as safe and effective cell-factories for food-application purposes. In this present study, we aimed at constitutive expression of a mannanase from Bacillus licheniformis DSM13, which was subsequently displayed on the cell surface of Lactobacillus plantarum WCFS1, for use as whole-cell biocatalyst in oligosaccharide production.

Results: Two strong constitutive promoters, Pgm and SlpA, from L. acidophilus NCFM and L. acidophilus ATCC4356, respectively, were used to replace the inducible promoter in the lactobacillal pSIP expression system for the construction of constitutive pSIP vectors. The mannanase-encoding gene (manB) was fused to the N-terminal lipoprotein anchor (Lp_1261) from L. plantarum and the resulting fusion protein was cloned into constitutive pSIP vectors and expressed in L. plantarum WCFS1. The localization of the protein on the bacterial cell surface was confirmed by flow cytometry and immunofluorescence microscopy. The mannanase activity and the reusability of the constructed L. plantarum displaying cells were evaluated. The highest mannanase activities on the surface of L. plantarum cells obtained under the control of the Pgm and SlpA promoters were 1200 and 3500 U/g dry cell weight, respectively, which were 2.6- and 7.8-fold higher compared to the activity obtained from inducible pSIP anchoring vectors. Surface-displayed mannanase was shown to be able to degrade galactomannan into manno-oligosaccharides (MOS).

Conclusion: This work demonstrated successful displaying of ManB on the cell surface of L. plantarum WCFS1 using constitutive promoter-based anchoring vectors for use in the production of manno-oligosaccharides, which are potentially prebiotic compounds with health-promoting effects. Our approach, where the enzyme of interest is displayed on the cell surface of a food-grade organism with the use of strong constitutive promoters, which continuously drive synthesis of the recombinant protein without the need to add an inducer or change the growth conditions of the host strain, should result in the availability of safe, stable food-grade biocatalysts.
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http://dx.doi.org/10.1186/s12934-019-1124-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6482533PMC
April 2019

β-Galactosidase from DSM 20075: Biochemical Characterization and Recombinant Expression for Applications in Dairy Industry.

Int J Mol Sci 2019 Feb 22;20(4). Epub 2019 Feb 22.

Food Biotechnology Laboratory, BOKU University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria.

β-Galactosidase encoding genes from DSM 20075 were cloned and successfully overexpressed in and using different expression systems. The highest recombinant β-galactosidase activity of ∼26 kU per L of medium was obtained when using an expression system based on the T7 RNA polymerase promoter in , which is more than 1000-fold or 28-fold higher than the production of native β-galactosidase from DSM 20075 when grown on glucose or lactose, respectively. The overexpression in using lactobacillal food-grade gene expression system resulted in ∼2.3 kU per L of medium, which is approximately 10-fold lower compared to the expression in . The recombinant β-galactosidase from overexpressed in was purified to apparent homogeneity and subsequently characterized. The and values for lactose and -nitrophenyl-β-d-galactopyranoside (NPG) were 15.7 ± 1.3 mM, 11.1 ± 0.2 µmol D-glucose released per min per mg protein, and 1.4 ± 0.3 mM, 476 ± 66 µmol -nitrophenol released per min per mg protein, respectively. The enzyme was inhibited by high concentrations of NPG with = 3.6 ± 0.8 mM. The optimum pH for hydrolysis of both substrates, lactose and NPG, is pH 6.5 and optimum temperatures for these reactions are 60 and 55 °C, respectively. The formation of galacto-oligosaccharides (GOS) in discontinuous mode using both crude recombinant enzyme from and purified recombinant enzyme from revealed high transgalactosylation activity of β-galactosidases from ; hence, this enzyme is an interesting candidate for applications in lactose conversion and GOS formation processes.
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http://dx.doi.org/10.3390/ijms20040947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412629PMC
February 2019

Expression and biochemical characterization of a new alkaline tannase from Lactobacillus pentosus.

Protein Expr Purif 2019 05 9;157:36-41. Epub 2019 Jan 9.

Division of Biotechnology, Faculty of Agro-Industry, Chiang Mai University, Chiang Mai, 50100, Thailand; Research Center for Multidisciplinary Approaches to Miang, Chiang Mai University, Chiang Mai, 50200, Thailand. Electronic address:

Lactobacillus pentosus BA-7 and L. pentosus QA1-5 are tannin-tolerant lactic acid bacteria that were isolated from Miang, a traditional fermented tea-leaf found in northern Thailand and a tannin-rich substrate. Tannase encoding genes were isolated, cloned and overexpressed in Escherichia coli BL21(DE3). The recombinant tannase was produced with production yields of 40 and 39 KU/L for LpTanBA-7 and LpTanQA1-5, respectively. Both revealed the same molecular weight of 50 kDa as estimated by SDS-PAGE and were optimally active under alkaline pH conditions LpTanQA1-5 revealed optimal temperatures in a range of 37-40 °C as is typically found in lactic acid bacteria, while LpTanBA-7 was active at higher temperatures with an optimum temperature range of 45-55 °C. LpTanBA-7 was found to be more stable within the same range of temperatures than LpTanQA1-5. Furthermore, it was active and stable toward various organic solvents and produced 50 mg/mL of gallic acid from 100 mg/mL tannic acid. Based on the results, LpTanBA-7 is considered a new alkali-moderately thermophilic tannase obtained from lactic acid bacterium that may be capable of a feasible production capacity of gallic acid and its esters. Furthermore, tannase that is active at high temperatures could also be used in tea products in order to develop a sweet aftertaste, as well as to improve levels of antioxidant activity.
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http://dx.doi.org/10.1016/j.pep.2019.01.005DOI Listing
May 2019

Fermentability of a Novel Galacto-Oligosaccharide Mixture by spp. and spp.

Molecules 2018 Dec 18;23(12). Epub 2018 Dec 18.

Food Biotechnology Laboratory, Department of Food Science and Technology, BOKU-University of Natural Resources and Life Sciences Vienna, A-1190 Vienna, Austria.

This study aimed to investigate the specific growth stimulation of certain desired intestinal bacteria by a novel galacto-oligosaccharide mixture, which was produced with a β-galactosidase from a potential probiotic isolate that contained mainly oligosaccharides of β-1,3 and β-1,6 glycosidic linkages (termed Lb-GOS) using single-strain fermentations. The composition of this Lb-GOS mixture was 33.5% disaccharides, 60.5% trisaccharides, 4.8% tetrasaccharides, and 1.0% pentasaccharides with a negligible amount of monosaccharides, lactose, and lactobionic acid (0.3%). Eight spp. strains and three spp. strains were used in single-strain fermentations to determine the fermentation activity scores of this Lb-GOS preparation compared to two commercially available prebiotic mixtures, 4'GOS-P and Vivinal GOS (V-GOS). The highest scores were obtained when Lb46 and the two strains, subsp. Bif1 and Bif3, were grown on these galacto-oligosaccharide mixtures. In addition, the Lb-GOS mixture was found to have higher fermentation activity scores; hence, it stimulated the growth of these probiotic strains more than 4'GOS-P and V-GOS, which may be attributed to the different glycosidic linkage types that are found in the Lb-GOS mixture compared to the other two commercial preparations. These findings suggested that the Lb-GOS mixture that is described in this work should be of interest for the formulations of new carbohydrate-based functional food ingredients.
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http://dx.doi.org/10.3390/molecules23123352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321129PMC
December 2018

Targeted knockout of phospholipase A to increase lipid productivity in Chlamydomonas reinhardtii for biodiesel production.

Bioresour Technol 2019 Jan 25;271:368-374. Epub 2018 Sep 25.

Department of Chemical and Biological Engineering, Korea University, 145, Anam-ro, Seoungbuk-gu, Seoul 02841, Republic of Korea. Electronic address:

Biofuel derived from microalgae have several advantages over other oleaginous crops, however, still needs to be improved with its cost aspect and can be achieved by developing of a strain with improved lipid productivity. In this study, the CRISPR-Cas9 system was incorporated to carry out a target-specific knockout of the phospholipase A gene in Chlamydomonas reinhardtii. The targeted gene encodes a key enzyme in the Lands cycle. As a result, the mutants showed a characteristic of increased diacylglycerol pool, followed by a higher accumulation of triacylglycerol without being significantly compensated with the cell growth. As a result, the overall lipid productivities of phospholipase A knockout mutants have increased by up to 64.25% (to 80.92 g L d). This study can provide crucial information for the biodiesel industry.
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http://dx.doi.org/10.1016/j.biortech.2018.09.121DOI Listing
January 2019

Micro food web networks on suspended sediment.

Sci Total Environ 2018 Dec 4;643:1387-1399. Epub 2018 Jul 4.

Laboratory for Advanced Environmental Engineering Research, School of Civil Engineering, The University of Sydney, Bld. J05, 2006 Sydney, NSW, Australia.

The genesis of suspended aggregates in aquatic ecosystems is not only a result of hydrodynamic mineral interactions but also a complex microbial food web network. A microbiological-physical model (BFLOC2) is introduced here to predict aggregate geometry and settling velocity under simultaneous effects of hydrodynamic and biological processes. While minerals can contribute to aggregate dynamics through collision, aggregation, and breakup, living microorganisms can colonize and establish food web interactions that involve growth and grazing, and modify the aggregate structure. The BFLOC2 model describes the aggregate dynamics resulting from interactions between minerals and three types of microorganisms, namely bacteria, flagellates, and ciliates. BFLOC2 was first calibrated against the size and capacity (fractal) dimension of aggregates formed in a pure mineral system at different mineral concentrations and fluid shear rates, and then against the abundance of aggregate-attached cells in a pure microbial environment. BFLOC2 model and calibrated parameters were then tested against biomineral aggregate size, capacity dimension, and biomass fraction formed in biomineral flocculation experiments at four nutrient concentrations. Modelling of biomineral aggregate dynamics over a wide range of environmental conditions showed that maximum aggregate size, biomass fraction, and settling velocity could occur at different optimal environmental conditions. Unlike mineral aggregates, which have maximum size when shear rate tends to zero, a relative maximum size of biomineral aggregates can be reached at intermediate shear rates as a result of microbiological processes. The settling velocity was ultimately controlled by aggregate size, capacity dimension, and biomass fraction. Microorganism dynamics including cell motility and food web network interactions significantly controlled aggregate-attached cell abundance and aggregate dynamics.
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http://dx.doi.org/10.1016/j.scitotenv.2018.06.247DOI Listing
December 2018
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