Publications by authors named "Verawat Champreda"

83 Publications

Characterization of Cellulose-Chitosan-Based Materials from Different Lignocellulosic Residues Prepared by the Ethanosolv Process and Bleaching Treatment with Hydrogen Peroxide.

ACS Omega 2021 Sep 23;6(35):22791-22802. Epub 2021 Aug 23.

The Joint Graduate School for Energy and Environment (JGSEE), King Mongkut's University of Technology Thonburi, Prachauthit Road, Bangmod, Bangkok 10140, Thailand.

Cellulose-based composites are promising biomaterials with potent applications in absorbents, cosmetics, and healthcare industries. In this study, the cellulose fractions from various agricultural residues, including bagasse (BG), rice straw (RS), corncob (CC), and palm fiber (PF), were prepared by the organosolv process using 70% v/v ethanol, followed by bleaching and forming with chitosan powder. Organosolv treatment at 180 °C of BG, RS, and PF and at 190 °C of CC for 60 min using HSO as the catalyst was optimal for high cellulose recovery (87.9-98.9%) with efficient removals of the hemicellulose (59.3-86.0%) and lignin (61.1-73.7%). High cellulose purity in the solids (76.9-86.8%) was obtained after bleaching with 4% v/v HO compared with that of 84.9% for commercial cellulose. The isolated celluloses were incubated with 2% w/v chitosan solution in acetic acid for the formation of the hydrogen-bonding interaction between the cellulose fiber and chitosan. The pieces of evidence of the obtained sheet materials were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and thermogravimetric analysis. All cellulose-chitosan materials absorbed water fraction in the range of 54.3-94.2 g/m. Efficient oil absorption was observed for cellulose-chitosan sheets prepared from PF (96.3 g/m) and CC (81.1 g/m). This work demonstrated the preparation of potent biobased absorbents with a promising application in waste treatment and healthcare industries.
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http://dx.doi.org/10.1021/acsomega.1c03141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8427791PMC
September 2021

Solvothermal-Based Lignin Fractionation From Corn Stover: Process Optimization and Product Characteristics.

Front Chem 2021 5;9:697237. Epub 2021 Aug 5.

School of Energy and Environment, University of Phayao, Muang Phayao, Thailand.

Fractionation of lignocellulosic is a fundamental step in the production of value-added biobased products. This work proposes an initiative to efficiently extract lignin from the corn stover using a single-step solvothermal fractionation in the presence of an acid promoter (HSO). The organic solvent mixture used consists of ethyl acetate, ethanol, and water at a ratio of 30: 25:45 (v/v), respectively. HSO was utilized as a promoter to improve the performance and selectivity of lignin removal from the solid phase and to increase the amount of recovered lignin in the organic phase. The optimal conditions for this extraction, based on response surface methodology (RSM), are a temperature of 180°C maintained for 49.1 min at an HSO concentration of 0.08 M. The optimal conditions show an efficient reaction with 98.0% cellulose yield and 75.0% lignin removal corresponding to 72.9% lignin recovery. In addition, the extracted lignin fractions, chemical composition, and structural features were investigated using Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D-HSQC NMR). The results indicate that the recovered lignin primarily contains a β-O-4 linking motif based on 2D-HSQC spectra. In addition, new C-C inter-unit linkages ( β-β, and β-5) are not formed in the recovered lignin during HSO-catalyzed solvothermal pretreatment. This work facilitates effective valorization of lignin into value-added chemicals and fuels.
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http://dx.doi.org/10.3389/fchem.2021.697237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8374146PMC
August 2021

Screening, cloning, expression and characterization of new alkaline trehalose synthase from and its application for trehalose production.

J Microbiol Biotechnol 2021 Aug 20;31(10). Epub 2021 Aug 20.

Enzyme Technology Research Team, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin RD., Klong Luang District, Pathumthani, 12120, Thailand.

Trehalose is a non-reducing disaccharide with an increasing demand for applications in food, nutraceutical, and pharmaceutical industries. Single step trehalose production by trehalose synthase (TreS) using maltose as a starting material is a promising alternative process for industrial application due to its simplicity and cost advantage. TBRC 1196 was identified using the developed screening method as a potent strain for TreS production. The TreS gene from TBRC 1196 was firstly cloned and expressed in . Purified recombinant trehalose synthase (PmTreS) had a molecular weight of 76 kDa and showed optimal pH and temperature at 9.0 and 40°C, respectively. The enzyme exhibited >90% residual activity under mesophilic condition under a broad pH range 7-10 for 6 hours. Maximum trehalose yield by PmTreS was 68.1% with low yield of glucose (4%) as a byproduct under optimal conditions, equivalent to productivity of 4.5 g/l/h using enzyme loading of 2 mg/g substrate and high concentration maltose solution (100 g/l) in a lab-scale bioreactor. The enzyme represents a potent biocatalyst for energy-saving trehalose production with potential on inhibiting microbial contamination by alkaline condition.
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http://dx.doi.org/10.4014/jmb.2106.06032DOI Listing
August 2021

Effects of Modified Activated Carbon on Microwave-Accelerated Organosolv Fractionation of Rice Husk.

ACS Omega 2021 Mar 12;6(8):5389-5398. Epub 2021 Feb 12.

School of Energy and Environment, University of Phayao, Tambon Maeka, Amphur Muang Phayao, Phayao 56000, Thailand.

Organosolv fractionation is a promising approach for the separation of lignocellulosic components in integrated biorefineries where each component can be fully valorized into valuable platform chemicals and biofuels. In this study, microwave-accelerated organosolv fractionation was developed for the modification of lignocellulosic fractionation of rice husk. The fractionation condition was optimized for 1 h with the microwave irradiation at 300 W using a ternary solvent mixture composed of 24%:32%:44% water/ethanol/methyl isobutyl ketone. The effects of mineral acids (HCl, HPO, and HSO) and heterogeneous acid promoters (HCl, HPO, and HSO impregnated over activated carbon) on the efficiency and selectivity of product yields (i.e., glucan, hemicellulose-derived products, and lignin) were also investigated. It was found that the use of HPO-activated carbon as the promoter showed superior performance on the fractionation of rice husk components, resulting in 88.8% recovery of cellulose, with 63.8% purity in the solid phase, whereas the recovery of hemicellulose (66.4%) with the lowest formation of furan and 5-hydroxymethyl furfural and lignin (81.0%) without sugar cross-contamination was obtained in the aqueous ethanol phase and organic phase, respectively. In addition, the morphology structure of fractionated rice husk presented 2.6-fold higher surface area (5.4 m/g) of cellulose-enriched fraction in comparison with the native rice husk (2.1 m/g), indicating the improvement of enzyme accessibility. Besides, the chemical changes of isolated lignin were also investigated by Fourier-transform infrared spectroscopy. This work gives pieces of information into the efficiencies of the microwave strategy as a climate neighborly elective fractionation method for this serious starting material in the biotreatment facility business.
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http://dx.doi.org/10.1021/acsomega.0c05575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7931405PMC
March 2021

Development of a CRISPR/Cpf1 system for targeted gene disruption in Aspergillus aculeatus TBRC 277.

BMC Biotechnol 2021 02 11;21(1):15. Epub 2021 Feb 11.

Institute of Molecular Biosciences, Mahidol University, Salaya, Nakhon Pathom, Thailand.

Background: CRISPR-Cas genome editing technologies have revolutionized biotechnological research particularly in functional genomics and synthetic biology. As an alternative to the most studied and well-developed CRISPR/Cas9, a new class 2 (type V) CRISPR-Cas system called Cpf1 has emerged as another versatile platform for precision genome modification in a wide range of organisms including filamentous fungi.

Results: In this study, we developed AMA1-based single CRISPR/Cpf1 expression vector that targets pyrG gene in Aspergillus aculeatus TBRC 277, a wild type filamentous fungus and potential enzyme-producing cell factory. The results showed that the Cpf1 codon optimized from Francisella tularensis subsp. novicida U112, FnCpf1, works efficiently to facilitate RNA-guided site-specific DNA cleavage. Specifically, we set up three different guide crRNAs targeting pyrG gene and demonstrated that FnCpf1 was able to induce site-specific double-strand breaks (DSBs) followed by an endogenous non-homologous end-joining (NHEJ) DNA repair pathway which caused insertions or deletions (indels) at these site-specific loci.

Conclusions: The use of FnCpf1 as an alternative class II (type V) nuclease was reported for the first time in A. aculeatus TBRC 277 species. The CRISPR/Cpf1 system developed in this study highlights the feasibility of CRISPR/Cpf1 technology and could be envisioned to further increase the utility of the CRISPR/Cpf1 in facilitating strain improvements as well as functional genomics of filamentous fungi.
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http://dx.doi.org/10.1186/s12896-021-00669-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7879532PMC
February 2021

Tropical and temperate wastewater treatment plants assemble different and diverse microbiomes.

Appl Microbiol Biotechnol 2021 Jan 6;105(2):853-867. Epub 2021 Jan 6.

IMCAS-RCEES joint lab at CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.

The diversity and assembly of activated sludge microbiomes play a key role in the performances of municipal wastewater treatment plants (WWTPs), which are the most widely applied biotechnological process systems. In this study, we investigated the microbiomes of municipal WWTPs in Bangkok, Wuhan, and Beijing that respectively represent tropical, subtropical, and temperate climate regions, and also explored how microbiomes assembled in these municipal WWTPs. Our results showed that the microbiomes from these municipal WWTPs were significantly different. The assembly of microbiomes in municipal WWTPs followed deterministic and stochastic processes governed by geographical location, temperature, and nutrients. We found that both taxonomic and phylogenetic α-diversities of tropical Bangkok municipal WWTPs were the highest and were rich in yet-to-be-identified microbial taxa. Nitrospirae and β-Proteobacteria were more abundant in tropical municipal WWTPs, but did not result in better removal efficiencies of ammonium and total nitrogen. Overall, these results suggest that tropical and temperate municipal WWTPs harbored diverse and unique microbial resources, and the municipal WWTP microbiomes were assembled with different processes. Implications of these findings for designing and running tropical municipal WWTPs were discussed. KEY POINTS: • Six WWTPs of tropical Thailand and subtropical and temperate China were investigated. • Tropical Bangkok WWTPs had more diverse and yet-to-be-identified microbial taxa. • Microbiome assembly processes were associated with geographical location.
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http://dx.doi.org/10.1007/s00253-020-11082-0DOI Listing
January 2021

Evaluation of rice straw biopowder from alkaline-mechanical pretreatment by hydro-textural approach.

Bioresour Technol 2021 Mar 29;323:124619. Epub 2020 Dec 29.

Department of Chemical and Process Engineering, The Sirindhorn International Thai German Graduate School of Engineering, King Mongkut's University of Technology North Bangkok, Bangkok, Thailand.

Apretreatment step forlignocelluloses is responsible to alter the complex structure which allows enhancingenzymatic accessibility and bioconversion of the materials.However, there is a gap on the methods to characterize physicalevolutions of the material throughout its pretreatment.The aim of this study is to evaluate the physical changes in rice straw (RS)pretreated with alkaline followed by grinding to produce biopowders.A hydro-textural approach was applied to evaluate the physical changes of RS pretreated byimpregnation and soaking in NaOH.The results indicated that the volume deformation increased by 110%, whilethe energy consumptiondecreased by 11.3% compared to unpretreated RS.Moreover, the cellulose content and glucose were 66.8 and 212 mg/gRS obtained by RSsoaking. Thealkaline-mechanicalpretreatment was shown asan effective process to providehigh glucosereadily converted to bioethanol.Additionally, the hydro-textural approach can be considered an alternative method for biomass structural characterization.
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http://dx.doi.org/10.1016/j.biortech.2020.124619DOI Listing
March 2021

Efficiency of Catalytic Liquid Hot Water Pretreatment for Conversion of Corn Stover to Bioethanol.

ACS Omega 2020 Nov 11;5(46):29872-29881. Epub 2020 Nov 11.

Integrated Biorefinery excellent Center (IBC), School of Energy and Environment, University of Phayao, Tambon Maeka, Amphur Muang, Phayao 56000, Thailand.

Lignocellulose is a promising raw material for the production of second-generation biofuels. In this study, the effects of acid-catalyzed liquid hot water (LHW) on pretreatment of corn stover (CS) for subsequent hydrolysis and conversion to ethanol were studied. The effects of reaction temperature, acid concentration, and residence time on glucose yield were evaluated using a response surface methodology. The optimal condition was 162.4 °C for 29.5 min with 0.45% v/v of sulfuric acid, leading to the maximum glucose yield of 91.05% from enzymatic hydrolysis of the cellulose-enriched fraction. Conversion of the solid fraction to ethanol by simultaneous saccharification and fermentation resulted in a theoretical ethanol yield of 93.91% based on digestible glucose. Scanning electron microscopy revealed disruption on the microstructure of the pretreated CS. Increases of crystallinity index and surface area of the pretreated biomass were observed along with alteration in the functional group profiles, as demonstrated by Fourier transform infrared spectroscopy. This work provides an insight into the effects of LHW on the enzymatic susceptibility and modification of the physicochemical properties of CS for further application on bioethanol production in biorefinery.
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http://dx.doi.org/10.1021/acsomega.0c04054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7689892PMC
November 2020

Identification and characterization of a novel AA9-type lytic polysaccharide monooxygenase from a bagasse metagenome.

Appl Microbiol Biotechnol 2021 Jan 24;105(1):197-210. Epub 2020 Nov 24.

Enzyme Technology Laboratory, Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Phahonyothin Road, Khlong Luang, Pathumthani, 12120, Thailand.

Lytic polysaccharide monooxygenases (LPMOs) are auxiliary enzymes catalyzing oxidative cleavages of cellulose chains in crystalline regions, resulting in their increasing accessibility to the hydrolytic enzyme counterparts and hence higher released sugars from biomass saccharification. In this study, a novel auxiliary protein family 9 LPMO (BgAA9) was identified from a metagenomic library derived from a thermophilic microbial community in bagasse collection site where diverse AA9 and AA10 putative sequences were annotated. The enzyme showed highest similarity to a glycoside hydrolase family 61 from Chaetomium thermophilum. Recombinant BgAA9 expressed in Pichia pastoris cleaved cellohexaose (DP6) into shorter cellooligosaccharides (DP2, DP3, and DP4). Supplementation BgAA9 to a commercial cellulase, Accellerase® 1500 showed strong synergistic effect on saccharification of Avicel® PH101, decrystallized cellulose, filter paper, and alkaline-pretreated sugarcane bagasse, resulting in 63-93% increase in the total reducing sugar yield after incubation at 50 °C for 72 h. Strong synergism was shown between BgAA9 and the cellulase with the highest total fermentable sugar yield obtained from 75:25% of Accellerase®1500:BgAA9 which released 39 mg glucose/FPU (filter paper unit) equivalent to 38.7% higher than Accellerase®1500 alone at the same total protein dosage of 5 mg/g substrate according to the mixture design study. The enzyme represented the first characterized LPMO from environmental metagenome and a potent auxiliary component for biomass saccharification. KEY POINTS: • BgAA9 represents the first characterized LPMO from metagenome. • 12 AA families were annotated in thermophilic bagasse fosmid library by NGS. • BgAA9 showed homology to Cel61 in Chaetomium thermophilum. • BgAA9 oxidized cellohexaose and PASC to DP2, DP4, and DP6. • BgAA9 showed strong synergism to Accellerase on bagasse hydrolysis.
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http://dx.doi.org/10.1007/s00253-020-11002-2DOI Listing
January 2021

Enhancement of catalytic performance of a metagenome-derived thermophilic oligosaccharide-specific xylanase by binding module removal and random mutagenesis.

J Biosci Bioeng 2021 Jan 14;131(1):13-19. Epub 2020 Oct 14.

Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, 113 Thailand Science Park, Phahonyothin Road, Khlong Luang, Pathumthani 12120, Thailand. Electronic address:

Xylo-oligosaccharide (XO) is a promising pre-biotic with applications in food, feed and healthcare products. XO can be produced by enzymatic digestion of xylan with xylanase. In this study, we aimed to improve the biochemical properties relevant to catalysis and kinetics of X11, a thermophilic glycosyl hydrolase (GH) family 11 endo-β-1,4-xylanase derived from a metagenomic library isolated from sugarcane bagasse, under high-temperature conditions preferred for XO synthesis. Removal of a carbohydrate-binding module (X11C) resulted in 6.5 fold greater catalytic efficiency. X11C was further improved by a Pro71Thr mutation in the X11P variant obtained from a random mutagenesis library, which exhibited 15.9 fold greater catalytic efficiency compared with wild-type X11 under the enzyme's optimal conditions of 80°C and pH 6.0. Homology modeling suggested that the improved performance of X11P could be attributed to formation of an extra H-bond between Thr71 and Ser75, which stabilizes the key catalytic residue Glu180 at the active pocket and β-sheet layers and agrees with the respective increase in melting temperature (T) where X11P >X11C >X11 as determined by differential scanning fluorimetry. The X11P variant was tested for hydrolysis of beechwood xylan, which showed X6 as the major product followed by X3 and X4 XOs. The highest yield of 5.5 g total XOs product/mg enzyme was observed for X11P, equivalent to 3.7 fold higher than that of wild-type with XO production of >800 mg/g xylan. The X11P enzyme could be developed as a thermophilic biocatalyst for XO synthesis in biorefineries.
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http://dx.doi.org/10.1016/j.jbiosc.2020.09.008DOI Listing
January 2021

Synergistic Effects of Co-Doping on Photocatalytic Activity of Titanium Dioxide on Glucose Conversion to Value-Added Chemicals.

ACS Omega 2020 Aug 6;5(32):20373-20381. Epub 2020 Aug 6.

Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan.

Development of conversion of biomass derivatives in combination with utilization of solar energy by photocatalysts is a promising alternative strategy for biorefineries. The photocatalytic reaction could convert glucose to a mixture of value-added chemicals under UV irradiation. Modifications of titanium dioxide (TiO) nanoparticles by metal or metalloid (i.e., B and Ag) and nonmetal (i.e., N) dopants were carried out. The effects of co-doping (i.e., B/N and Ag/N) on physicochemical characteristics of the modified photocatalysts, photocatalytic glucose conversion, and the yields of the target chemical products (i.e., gluconic acid, xylitol, arabinose, and formic acid) were studied. The doping of the photocatalysts by different single dopants could improve the performance in terms of productivity and was further enhanced by the synergism from co-doping. The improvement in catalytic performances of the photocatalysts corresponded with the alterations in physicochemical characteristics of the catalysts resulting from the dopants.
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http://dx.doi.org/10.1021/acsomega.0c02334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7439370PMC
August 2020

Engineering of β-mannanase from Aspergillus niger to increase product selectivity towards medium chain length mannooligosaccharides.

J Biosci Bioeng 2020 Nov 26;130(5):443-449. Epub 2020 Jul 26.

Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Phaholyothin Road, Khlong Luang, Pathumthani 12120, Thailand.

Mannooligosaccharides (MOSs) are one of the most commonly used biomass-derived feed additives. The effectiveness of MOS varies with the length of oligosaccharides, medium length MOSs such as mannotetraose and mannopentaose being the most efficient. This study aims at improving specificity of β-mannanase from Aspergillus niger toward the desirable product size through rational-based enzyme engineering. Tyr 42 and Tyr 132 were mutated to Gly to extend the substrate binding site, allowing higher molecular weight MOS to non-catalytically bind to the enzyme. Hydrolysis product content was analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. Instead of mannobiose, the enzyme variants yielded mannotriose and mannotetraose as the major products, followed by mannobiose and mannopentaose. Overall, 42% improvement in production yield of highly active mannotetraose and mannopentaose was achieved. This validates the use of engineered β-mannanase to selectively produce larger MOS, making them promising candidates for large-scale MOS enzymatic production process.
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http://dx.doi.org/10.1016/j.jbiosc.2020.07.001DOI Listing
November 2020

Global Reprogramming of Gene Transcription in by Overexpressing an Artificial Transcription Factor for Improved Cellulase Production and Identification of Ypr1 as an Associated Regulator.

Front Bioeng Biotechnol 2020 3;8:649. Epub 2020 Jul 3.

State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.

Synthetic biology studies on filamentous fungi are providing unprecedented opportunities for optimizing this important category of microbial cell factory. Artificial transcription factor can be designed and used to offer novel modes of regulation on gene transcription network. is commonly used for cellulase production. In our previous studies, a plasmid library harboring genes encoding artificial zinc finger proteins (AZFPs) was constructed for engineering , and the mutant strains with improved cellulase production were selected. However, the underlying mechanism by which AZFP function remain unclear. In this study, a Rut-C30 mutant strain U5 bearing an AZFP named as AZFP-U5 was focused, which secretes high level protein and shows significantly improved cellulase and xylanase production comparing with its parental strain. In addition, enhanced sugar release was achieved from lignocellulosic biomass using the crude cellulase from U5. Comparative transcriptome analysis was further performed, which showed reprogramming of global gene transcription and elevated transcription of genes encoding glycoside hydrolases by overexpressing . Furthermore, 15 candidate regulatory genes which showed remarkable higher transcription levels by insertion were overexpressed in Rut-C30 to examine their effects on cellulase biosynthesis. Among these genes, () and showed stimulating effects on filter paper activity (FPase), but deletion of these two genes did not affect cellulase activity. In addition, increased yellow pigment production in Rut-C30 by overexpression of gene was observed, and changes of cellulase gene transcription were revealed in the deletion mutant, suggesting possible interaction between pigment production and cellulase gene transcription. The results in this study revealed novel aspects in regulation of cellulase gene expression by the artificial regulators. In addition, the candidate genes and processes identified in the transcriptome data can be further explored for synthetic biology design and metabolic engineering of to enhance cellulase production.
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http://dx.doi.org/10.3389/fbioe.2020.00649DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7351519PMC
July 2020

Improvement in D-xylose utilization and isobutanol production in S. cerevisiae by adaptive laboratory evolution and rational engineering.

J Ind Microbiol Biotechnol 2020 Jul 19;47(6-7):497-510. Epub 2020 May 19.

National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Paholyothin Road, Klong 1, Klong Luang, 12120, Pathumthani, Thailand.

As the effects of climate change become apparent, metabolic engineers and synthetic biologists are exploring sustainable sources for transportation fuels. The design and engineering of microorganisms to produce gasoline, diesel, and jet fuel compounds from renewable feedstocks can significantly reduce our dependence on fossil fuels as well as lower the emissions of greenhouse gases. Over the past 2 decades, a considerable amount of work has led to the development of microbial strains for the production of advanced fuel compounds from both C5 and C6 sugars. In this work, we combined two strategies-adaptive laboratory evolution and rational metabolic engineering-to improve the yeast Saccharomyces cerevisiae's ability to utilize D-xylose, a major C5 sugar in biomass, and produce the advanced biofuel isobutanol. Whole genome resequencing of several evolved strains followed by reverse engineering identified two single nucleotide mutations, one in CCR4 and another in TIF1, that improved the yeast's specific growth rate by 23% and 14%, respectively. Neither one of these genes has previously been implicated to play a role in utilization of D-xylose. Fine-tuning the expression levels of the bottleneck enzymes in the isobutanol pathway further improved the evolved strain's isobutanol titer to 92.9 ± 4.4 mg/L (specific isobutanol production of 50.2 ± 2.6 mg/g DCW), a 90% improvement in titer and a 110% improvement in specific production over the non-evolved strain. We hope that our work will set the stage for an economic route to the advanced biofuel isobutanol and enable efficient utilization of xylose-containing biomass.
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http://dx.doi.org/10.1007/s10295-020-02281-9DOI Listing
July 2020

Comparative analysis of bacterial communities associated with healthy and diseased corals in the Indonesian sea.

PeerJ 2019 19;7:e8137. Epub 2019 Dec 19.

Biorefinery and Bioproduct Technology Research Group, National Center for Genetic Engineering and Biotechnology, Pathum Thani, Thailand.

Coral reef ecosystems are impacted by climate change and human activities, such as increasing coastal development, overfishing, sewage and other pollutant discharge, and consequent eutrophication, which triggers increasing incidents of diseases and deterioration of corals worldwide. In this study, bacterial communities associated with four species of corals: , , sp., and sp. in the healthy and disease stages with different diseases were compared using tagged 16S rRNA sequencing. In total, 59 bacterial phyla, 190 orders, and 307 genera were assigned in coral metagenomes where and were pre-dominated followed by together with , , and as minor taxa. Principal Coordinates Analysis (PCoA) showed separated clustering of bacterial diversity in healthy and infected groups for individual coral species. was found as the major bacterial genus across all corals. The lower number of was found in infected with white band disease and sp. with white plaque disease, but marked increases of and , respectively, were observed. This was in contrast to infected by a black band and sp. infected by yellow blotch diseases which showed an increasing abundance of but a decrease in WH1-8 bacteria. Overall, infection was shown to result in disturbance in the complexity and structure of the associated bacterial microbiomes which can be relevant to the pathogenicity of the microbes associated with infected corals.
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http://dx.doi.org/10.7717/peerj.8137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6925950PMC
December 2019

Biofilm Reactor for Ethanol Production Using Rice Straw Hydrolysate Under Continuous and Repeated Batch Processes.

Front Microbiol 2019 7;10:1777. Epub 2019 Aug 7.

National Center for Genetic Engineering and Biotechnology (BIOTEC), Klong Luang, Thailand.

Plastic composited corn silk was developed as a biotic/abiotic carrier for biofilm formation for the purpose of ethanol production. Furthermore, we explored the use of rice straw hydrolysate as substrate in both multistage continuous culture and repeated batch processes and compared the ethanol production efficiency by two strains of . Biofilm formed by bacterial strains ZM4 and TISTR551 were detected, and its proficiencies were compared under various conditions by scanning electron microscopy (SEM) and crystal violet assays. The greatest biofilm formed by both strains was found on day five after the inoculation. strain ZM4 grown in repeated batch biofilm reactors produced higher yields of ethanol than TISTR551 grown under the same conditions, while TISTR551 produced higher yields of ethanol in the multistage continuous process. The yields were highly maintained, with no significant differences ( < 0.05) among the three consecutive repeated batches. These experiments highlight exciting uses for agricultural byproducts in the production of ethanol using biofilm reactors.
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http://dx.doi.org/10.3389/fmicb.2019.01777DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6693309PMC
August 2019

Evaluation of combined semi-humid chemo-mechanical pretreatment of lignocellulosic biomass in energy efficiency and waste generation.

Bioresour Technol 2019 Nov 7;292:121966. Epub 2019 Aug 7.

BIOTEC-JGSEE Integrative Biorefinery Laboratory, Innovation Cluster 2 Building, Thailand Science Park, Phaholyothin Road, Khlong Luang, Pathumthani 12120, Thailand; Joint Graduate School for Energy and Environment (JGSEE), King Mongkut's University of Technology Thonburi, Bangmod, Bangkok 10140, Thailand.

A combination of chemo-mechanical pretreatment of lignocellulosic biomass was developed with objectives to evaluate and optimize the energy efficiency and waste generation occurred in the pretreatment process. Sugarcane bagasse (SCB) was chemically pretreated with alkaline and alkaline peroxide followed by mechanical size reduction and enzymatic hydrolysis. The high solid and low solid loading pretreatments were studied to compare the total energy consumption, energy efficiency as well as waste generation. SCBSHNa (1:5) namely semi-humid chemo-mechanical pretreatment was found as the most effective pretreatment by decreasing 65% of total energy consumption. Moreover, the SCBSHNa (1:5) achieved the highest energy efficiency resulting in 0.536 kg reducing sugars/kWh and generated 0.33 kg of waste/kg reducing sugars. The developed process represented the advantages on energy efficiency and less waste generation compared to the conventional chemical soaking pretreatment process.
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http://dx.doi.org/10.1016/j.biortech.2019.121966DOI Listing
November 2019

Designing cellulolytic enzyme systems for biorefinery: From nature to application.

J Biosci Bioeng 2019 Dec 13;128(6):637-654. Epub 2019 Jun 13.

National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Phahonyothin Road, Khlong Luang, Pathumthani 12120, Thailand.

Cellulolytic enzymes play a key role on conversion of lignocellulosic plant biomass to biofuels and biochemicals in sugar platform biorefineries. In this review, we survey composite carbohydrate-active enzymes (CAZymes) among groups of cellulolytic fungi and bacteria that exist under aerobic and anaerobic conditions. Recent advances in designing effective cellulase mixtures are described, starting from the most complex microbial consortium-based enzyme preparations, to single-origin enzymes derived from intensively studied cellulase producers such as Trichoderma reesei, Talaromyces cellulolyticus, and Penicellium funiculosum, and the simplest minimal enzyme systems comprising selected sets of mono-component enzymes tailor-made for specific lignocellulosic substrates. We provide a comprehensive update on studies in developing high-performance cellulases for biorefineries.
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http://dx.doi.org/10.1016/j.jbiosc.2019.05.007DOI Listing
December 2019

Identification and evaluation of novel anchoring proteins for cell surface display on Saccharomyces cerevisiae.

Appl Microbiol Biotechnol 2019 Apr 9;103(7):3085-3097. Epub 2019 Feb 9.

Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, 113 Thailand Science Park, Klong Luang, Pathumthani, 12120, Thailand.

The development of arming yeast strains as whole-cell biocatalysts involves a selection of effective anchoring proteins to display enzymes and proteins on yeast cell surface. To screen for novel anchoring proteins with improved efficiency, a bioinformatics pipeline for the identification of glycosylphosphatidylinositol-anchored cell wall proteins (GPI-CWPs) suitable for attaching passenger proteins to the cell surface of Saccharomyces cerevisiae has been developed. Here, the C-terminal sequences (CTSs) of putative GPI-CWPs were selected based on the criteria that the sequence must contain a serine/threonine-rich (S/T) region of at least 30% S/T content, a total threonine content of at least 10%, a continuous S/T stretch of at least 130 amino acids in length, and a continuous T-rich region of at least 10 amino acids in length. Of the predicted 790 proteins, 37 putative GPI-CWPs were selected from different yeast and fungal species to be evaluated for their performance in displaying yeast-enhanced green fluorescent protein and β-glucosidase enzyme. This led to the identification of five novel anchoring proteins with higher performance compared to α-agglutinin used as benchmark. In particular, the CTS of uncharacterized protein in Kluyveromyces lactis, namely 6_Kl, is the most efficient anchoring protein of the group. The CTS of 6_Kl protein provided a β-glucosidase activity of up to 23.5 U/g cell dry weight, which is 2.8 times higher than that of the CTS of α-agglutinin. These identified CTSs could be potential novel anchoring protein candidates for construction of efficient arming yeasts for biotechnology applications in the future.
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http://dx.doi.org/10.1007/s00253-019-09667-5DOI Listing
April 2019

Biosurfactant-Producing Capability and Prediction of Functional Genes Potentially Beneficial to Microbial Enhanced Oil Recovery in Indigenous Bacterial Communities of an Onshore Oil Reservoir.

Curr Microbiol 2019 Mar 8;76(3):382-391. Epub 2019 Feb 8.

Division of Microbiology, Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand.

Microbial enhanced oil recovery (MEOR) is a bio-based technology with economic and environmental benefits. The success of MEOR depends greatly on the types and characteristics of indigenous microbes. The aim of this study was to evaluate the feasibility of applying MEOR at Mae Soon Reservoir, an onshore oil reservoir experiencing a decline in its production rate. We investigated the capability of the reservoir's bacteria to produce biosurfactants, and evaluated the potentials of uncultured indigenous bacteria to support MEOR by means of prediction of MEOR-related functional genes, based on a set of metagenomic 16s rRNA gene data. The biosurfactant-producing bacteria isolated from the oil-bearing sandstones from the reservoir belonged to one species: Bacillus licheniformis, with one having the ability to decrease surface tension from 72 to 32 mN/m. Gene sequences responsible for biosurfactant (licA3), lipase (lipP1) and catechol 2,3-dioxygenase (C23O) were detected in these isolates. The latter two, and other genes encoding MEOR-related functional proteins such as enoyl-CoA hydratase and alkane 1-monooxygenase, were predicted in the bacterial communities residing the reservoir's sandstones. Exposure of these sandstones to nutrients, consisting of KNO and NaHPO, resulted in an increase in the proportions of some predicted functional genes. These results indicated the potentials of MEOR application at Mae Soon site. Using the approaches demonstrated in this study would also assist evaluation of the feasibility of applying MEOR in oil reservoirs, which may be enhanced by an appropriate nutrient treatment.
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http://dx.doi.org/10.1007/s00284-019-01641-8DOI Listing
March 2019

Effect of inorganic nutrients on bacterial community composition in oil-bearing sandstones from the subsurface strata of an onshore oil reservoir and its potential use in Microbial Enhanced Oil Recovery.

PLoS One 2018 29;13(11):e0198050. Epub 2018 Nov 29.

Environmental Science Research Centre (ESRC), Faculty of Science, Chiang Mai University, Chiang Mai, Thailand.

Microbial Enhanced Oil Recovery (MEOR) is a promising strategy to improve recovery of residual oil in reservoirs, which can be performed by promoting specific indigenous microorganisms. In this study, we performed preliminary evaluation of the possibility of conducting MEOR at Mae Soon reservoir, an onshore reservoir in Northern Thailand. The reservoir's physicochemical characteristics, including the characteristics of the wells, the oil-bearing sandstone cores, and the reservoir's produced water, were determined. The microbiological characteristics of the oil wells in the reservoir were also investigated by submerging the reservoir's sandstone core samples, obtained from 6 oil wells, in the reservoir's produced water and in the produced water added with inorganic nutrients (KNO3 and NaH2PO4). The uncultured bacteria in both treatments were determined, using tagged 16S rRNA gene amplicon with Ion Torrent Sequencing Analysis. The effects of inorganic nutrients and the reservoir's parameters on the bacterial communities were analysed. A total number of 16,828 OTUs were taxonomically classified into 89 classes and 584 genera. In the controls (sandstone cores submerged in the produced water), the dominant bacterial populations were related to Deinococcus-Thermus, and Betaproteobacteria; while in the nutrient treated samples, there was a marked increase in the relative abundance of Gammaproteobacteria in three samples. Thermus, Acinetobacter, and Pseudomonas were the most abundant genera, and these are potential microorganisms for MEOR. Analysis of correlations between physiochemical properties of the reservoir and bacterial genera, using spearman's correlation analysis, suggested that some of the reservoir's properties, especially of the well and the rock, could influence some bacterial genera. To our knowledge, this is the first demonstration of the effect of inorganic nutrients on alteration of bacterial communities attached to reservoir's rock, and how the bacterial, physical, and chemical properties of a reservoir were co-analysed to serve as a basis for designing a MEOR process.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198050PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6264815PMC
April 2019

Elucidating cellular mechanisms of Saccharomyces cerevisiae tolerant to combined lignocellulosic-derived inhibitors using high-throughput phenotyping and multiomics analyses.

FEMS Yeast Res 2018 12;18(8)

National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park Paholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand.

A robust cell factory that can tolerate combined inhibitory lignocellulosic compounds is essential for the cost-effective lignocellulose-based production of second-generation bioethanol and other bulk chemicals. Following high-throughput phenotyping of a yeast genomic overexpression library, we identified a Saccharomyces cerevisiae mutant (denoted AFb.01) with improved growth and fermentation performance under combined toxicity of acetic acid and furfural. AFb.01 carries overexpression of TRX1, which encodes for thioredoxin, a cellular redox machinery. Through comparative proteomics and metabolomics, the resulting cell-wide changes in the mutant were elucidated and these primarily target on the maintenance of energy and redox homeostasis and the minimization of stress-induced cell damages. In particular, the upregulation of the stress-response proteins Hsp26p and Fmp16p conferred tolerance of AFb.01 against protein denaturation and DNA damage. Moreover, increased levels of protectant metabolites such as trehalose, fatty acids, GABA and putrescine provided additional defense mechanisms for the mutant against oxidative and redox stresses. Future studies will concentrate on targeted genetic engineering to validate these mechanisms as well as to support the creation of more robust yeast strains, applicable for industrial, cost-competitive biorefinery production.
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http://dx.doi.org/10.1093/femsyr/foy106DOI Listing
December 2018

Synthesis and characterization of Ogataea thermomethanolica alcohol oxidase immobilized on barium ferrite magnetic microparticles.

J Biosci Bioeng 2019 Mar 20;127(3):265-272. Epub 2018 Sep 20.

Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Phahonyothin Road, Khlong Luang, Pathum Thani 12120, Thailand; JGSEE-BIOTEC Integrative Biorefinery Laboratory, National Center for Genetic Engineering and Biotechnology, Innovative Cluster 2 Building, Phahonyothin Road, Khlong Luang, Pathum Thani 12120, Thailand. Electronic address:

Alcohol oxidase catalyzes the oxidation of primary alcohols into the corresponding aldehydes, making it a potential biocatalyst in the chemical industry. However, the high production cost and poor operational stability of this enzyme are limitations for industrial application. Immobilization of enzyme onto solid supports is a useful strategy for improving enzyme stability. In this work, alcohol oxidase from the thermotolerant methylotrophic yeast Ogataea thermomethanolica (OthAOX) was covalently immobilized onto barium ferrite (BaFeO) magnetic microparticles. Among different conditions tested, the highest immobilization efficiency of 71.0 % and catalytic activity of 34.6 U/g was obtained. Immobilization of OthAOX onto magnetic support was shown by Fourier-Transformed infrared microscopy, scanning electron microscopy and X-ray diffraction. The immobilized OthAOX worked optimally at 55 °C and pH 8.0. Immobilization also improved thermostability, in which >65% of the initial immobilized enzyme activity was retained after 24 h pre-incubation at 45 °C. The immobilized enzyme showed a greater catalytic efficiency for oxidation of methanol and ethanol than free enzyme. The immobilized enzyme could be recovered by magnetization and recycled for at least three consecutive batches, after which 70% activity remained. The properties of the immobilized enzyme suggest its potential industrial application for synthesis of aldehyde.
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http://dx.doi.org/10.1016/j.jbiosc.2018.08.007DOI Listing
March 2019

Expression and Extracellular Secretion of Endo-glucanase and Xylanase by Zymomonas mobilis.

Appl Biochem Biotechnol 2019 Jan 19;187(1):239-252. Epub 2018 Jun 19.

National Center for Genetic Engineering and Biotechnology (BIOTEC), Thailand Science Park, Phahonyothin Road, Klong Luang, Pathumthani, 12120, Thailand.

Recombinant Zymomonas mobilis (pGEX-4T-3 BI 120-2) was constructed to encode endo-glucanase (CelA) and endo-xylanase (Xyn11) from Z. mobilis ZM4 (ATCC 31821) and an uncultured bacterium. The recombinant was genetically engineered with the N-terminus of a predicted SecB-dependent (type II) secretion signal from phoC of Z. mobilis to translocate the enzymes extracellularly. Both the enzymes were characterized regarding their functional optimum pH and temperature, with the highest multi-enzyme activities at pH 6.0 and a temperature of 30 °C, which approximates the optimum conditions for ethanol production by Z. mobilis. The crude intracellular and extracellular fractions of the recombinant were characterized in terms of substrate specificity using carboxymethyl cellulose (CMC), beechwood xylan, filter paper, Avicel, and pretreated rice straw. The crude extracellular and intracellular enzymes with cellulolytic and xylanolytic activities were more robustly produced and secreted from the recombinant strain compared to the wild-type and ampicillin-sensitive strains, using CMC and beechwood xylan as the substrates. Ethanol production by the recombinant strain was greater than the production by the wild-type strain when pretreated rice straw was used as a sole carbon source.
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http://dx.doi.org/10.1007/s12010-018-2821-4DOI Listing
January 2019

Purification, characterization, and stabilization of alcohol oxidase from Ogataea thermomethanolica.

Protein Expr Purif 2018 10 5;150:26-32. Epub 2018 May 5.

Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology, Phahonyothin Road, Khlong Luang, Pathum Thani 12120, Thailand; JGSEE-BIOTEC Integrative Biorefinery Laboratory, National Center for Genetic Engineering and Biotechnology, Innovative Cluster 2 Building, Phahonyothin Road, Khlong Luang, Pathum Thani 12120, Thailand. Electronic address:

Alcohol oxidase (AOX) functions in oxidation of primary alcohols into the corresponding aldehydes with potential on catalyzing synthesis reactions in chemical industry. In this study, AOX from a thermotolerant methylotrophic yeast, Ogataea thermomethanolica (OthAOX) was purified to high homogeneity using a single step chromatographic separation on a DEAE-Sepharose column. The purified OthAOX had a specific activity of 15.34 U/mg with 77.5% recovery yield. The enzyme worked optimally at 50 °C in an alkaline range (pH 9.0). According to kinetic analysis, OthAOX showed a higher affinity toward short-chain aliphatic primary alcohol with the V, K, and k of 0.24 nmol/min, 0.27 mM, and 3628.8 min, respectively against methanol. Addition of alginic acid (0.35%) showed a protective effect on enhancing thermal stability of the enzyme, resulting in 72% increase in its half-life at 40 °C under the operational conditions. This enzyme represents a promising candidate for conversion of bioethanol to acetaldehyde as secondary chemical in biorefinery.
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http://dx.doi.org/10.1016/j.pep.2018.05.001DOI Listing
October 2018

Fractionation of lignocellulosic biopolymers from sugarcane bagasse using formic acid-catalyzed organosolv process.

3 Biotech 2018 May 17;8(5):221. Epub 2018 Apr 17.

1The Joint Graduate School for Energy and Environment (JGSEE), King Mongkut's University of Technology Thonburi, Prachauthit Road, Bangmod, Bangkok, 10140 Thailand.

A one-step formic acid-catalyzed organosolv process using a low-boiling point acid-solvent system was studied for fractionation of sugarcane bagasse. Compared to HSO, the use of formic acid as a promoter resulted in higher efficiency and selectivity on removals of hemicellulose and lignin with increased enzymatic digestibility of the cellulose-enriched solid fraction. The optimal condition from central composite design analysis was determined as 40 min residence time at 159 °C using water/ethanol/ethyl acetate/formic acid in the respective ratios of 43:20:16:21%v/v. Under this condition, a 94.6% recovery of cellulose was obtained in the solid with 80.2% cellulose content while 91.4 and 80.4% of hemicellulose and lignin were removed to the aqueous-alcohol-acid and ethyl acetate phases, respectively. Enzymatic hydrolysis of the solid yielded 84.5% glucose recovery compared to available glucan in the raw material. Physicochemical analysis revealed intact cellulose fibers with decreased crystallinity while the hemicellulose was partially recovered as mono- and oligomeric sugars. High-purity organosolv lignin with < 1% sugar cross-contamination was obtained with no major structural modification according to Fourier-transform infrared spectroscopy. The work represents an alternative process for efficient fractionation of lignocellulosic biomass in biorefineries.
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http://dx.doi.org/10.1007/s13205-018-1244-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5902339PMC
May 2018

Development of tailor-made synergistic cellulolytic enzyme system for saccharification of steam exploded sugarcane bagasse.

J Biosci Bioeng 2018 Apr 28;125(4):390-396. Epub 2017 Dec 28.

Enzyme Technology Laboratory, Microbial Biotechnology and Biochemicals Research Unit, National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Khlong Luang, Pathumthani 12120, Thailand. Electronic address:

Designing a tailor-made synergistic system is a promising strategy for developing an effective enzyme for saccharification of lignocellulosic materials. In this study, a cellulolytic enzyme mixture comprising selected core recombinant enzymes for hydrolysis of sugarcane bagasse pretreated by alkaline-catalyzed steam explosion was optimized using a mixture design approach. The optimized enzyme system comprised a cellobiohydrolase (Cel7A) from Talaromyces cellulolyticus, an endo-glucanase (Cel7B) from Thielavia terrestris, a β-glucosidase (BGL) and an endo-β1,4-xylanase (XYN) from Aspergillus aculeatus at the ratio of 0.34:0.27:0.14:0.25. The maximum reducing sugar yield of 797 mg/g biomass, comprising 543 and 96.8 mg/g glucose and xylose, respectively were achieved, equivalent to 92.44% and 47.50% recoveries, respectively from the pretreated substrate at the enzyme dosage of 20 mg/g biomass. The sugar yield from the quaternary enzyme mixture was 17.37% higher than that obtained with Accellerase 1500.
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http://dx.doi.org/10.1016/j.jbiosc.2017.11.001DOI Listing
April 2018

Characterization of cellulolytic microbial consortium enriched on Napier grass using metagenomic approaches.

J Biosci Bioeng 2018 Apr 21;125(4):439-447. Epub 2017 Nov 21.

Enzyme Technology Laboratory, National Center for Genetic Engineering and Biotechnology, 113 Thailand Science Park, Pahonyothin Road, Klong Luang, Pathum Thani 12120, Thailand.

Energy grass is a promising substrate for production of biogas by anaerobic digestion. However, the conversion efficiency is limited by the enzymatically recalcitrant nature of cellulosic wastes. In this study, an active, structurally stable mesophilic lignocellulolytic degrading microbial consortium (Np-LMC) was constructed from forest compost soil microbiota by successive subcultivation on Napier grass under facultative anoxic conditions. According to tagged 16S rRNA gene amplicon sequencing, increasing abundance of facultative Proteobacteria was found in the middle of batch cycle which was then subsequently replaced by the cellulose degraders Firmicutes and Bacteroidetes along with decreasing CMCase, xylanase, and β-glucanase activity profiles in the supernatant after 5 days of incubation. Anaerobic/facultative bacteria Dysgonomonas and Sedimentibacter and aerobic bacteria Comamonas were the major genera found in Np-LMC. The consortium was active on degradation of the native and delignified grass. Direct shotgun sequencing of the consortium metagenome revealed relatively high abundance of genes encoding for various lignocellulose degrading enzymes in 23 glycosyl hydrolase (GH) families compared to previously reported cellulolytic microbial communities in mammalian digestive tracts. Enzymes attacking cellulose and hemicellulose were dominated by GH2, 3, 5, 9, 10, 26, 28 and 43 in addition to a variety of carbohydrate esterases (CE) and auxiliary activities (AA), reflecting adaptation of the enzyme systems to the native herbaceous substrate. The consortium identified here represents the microcosm specifically bred on energy grass, with potential for enhancing degradation of fibrous substrates in bioenergy industry.
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http://dx.doi.org/10.1016/j.jbiosc.2017.10.014DOI Listing
April 2018

Effects of alkaline catalysts on acetone-based organosolv pretreatment of rice straw.

3 Biotech 2017 Oct 21;7(5):340. Epub 2017 Sep 21.

The Joint Graduate School for Energy and Environment (JGSEE), King Mongkut's University of Technology Thonburi, Prachauthit Road, Bangmod, Bangkok, 10140 Thailand.

Organosolv is an effective pretreatment strategy for increasing digestibility of lignocellulosic materials owing to selectivity of solvents on separating biopolymeric constituents of plant biomass. In the present work, a novel low-temperature alkali-catalyzed organosolv pretreatment of rice straw was studied. The effects of alkaline catalysts (i.e., NaOH, ammonia, and tri-ethylamine) and solvent types (i.e., acetone, ethanol, and water) were carried out. Addition of alkalis led to increasing sugar from enzymatic hydrolysis while acetone was found to be superior to ethanol and water on selectivity towards cellulose preservation. The optimal alkaline-catalyzed pretreatment reaction contained 5% (w/v) NaOH in an aqueous-acetone mixture (1:4) at 80 °C for 5 min. A glucose yield of 913 mg/g of pretreated biomass was achieved, equivalent to a maximal glucose recovery of 93.0% from glucan in the native biomass. Scanning electron microscope revealed efficient removal of non-cellulosic components, resulting in exposed cellulose microfibers with a reduced crystallite size as determined by X-ray diffraction. With potential on obtaining high-quality lignin, the work demonstrated potential of the novel low-temperature alkaline-catalyzed acetone-based organosolv process for pretreatment of lignocellulosic materials in biorefineries.
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http://dx.doi.org/10.1007/s13205-017-0969-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607077PMC
October 2017
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