Publications by authors named "Carmen Wacher"

20 Publications

  • Page 1 of 1

Microbial Interactions between Amylolytic and Non-Amylolytic Lactic Acid Bacteria Strains Isolated during the Fermentation of Pozol.

Foods 2021 Oct 28;10(11). Epub 2021 Oct 28.

Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico.

Pozol is a Mexican beverage prepared from fermented nixtamalized maize dough. To contribute to understanding its complex microbial ecology, the effect of inoculating on MRS-starch pure and mixed cultures of amylolytic -25124 and non-amylolytic 17, isolated from pozol, were studied on their interactions and fermentation parameters. These were compared with A6, an amylolytic strain isolated from cassava. Microbial growth, kinetic parameters, amylolytic activity, lactic acid production, and hydrolysis products from starch fermentation were measured. The population dynamics were followed by qPCR. A6 showed higher enzymatic activity, lactic acid, biomass production, and kinetic parameters than pozol LAB in pure cultures. Mixed culture of each pozol LAB with A6 showed a significant decrease in amylolytic activity, lactic acid yield, specific growth rate, and specific rate of amylase production. The interaction between -25124 and 17 increased the global maximum specific growth rate (µ), the lactic acid yield from starch (Y lactic acid yield from biomass (Y), and specific rate of lactic acid production (q) by 15, 30, 30, and 40%, respectively, compared with the pure culture of -25124. Interactions between the two strains are essential for this fermentation.
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http://dx.doi.org/10.3390/foods10112607DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8622207PMC
October 2021

Metaproteomic Insights Into the Microbial Community in Pozol.

Front Nutr 2021 20;8:714814. Epub 2021 Aug 20.

Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico.

Pozol is an acidic, refreshing, and non-alcoholic traditional Mayan beverage made with nixtamalized corn dough that is fermented spontaneously. The extensive analysis of the microbiology, biochemistry and metaproteomics of pozol allowed the construction of a comprehensive image of the fermentation system. The main changes in both the substrate and the microbiota occurred in the first 9 h of fermentation. The increase in microorganisms correlated with the drop in pH and with the decrease in the contents of carbohydrates, lipids, and nitrogen, which shows that this stage has the highest metabolic activity. Bacterial proteins were mainly represented by those of lactic acid bacteria, and among them, the proteins from genus was overwhelmingly the most abundant. Yeast proteins were present in all the analyzed samples, while proteins from filamentous fungi increased up to 48 h. The metaproteomic approach allowed us to identify several previously unknown enzyme complexes in the system. Additionally, enzymes for hydrolysis of starch, hemicellulose and cellulose were found, indicating that all these substrates can be used as a carbon source by the microbiota. Finally, enzymes related to the production of essential intermediates involved in the synthesis of organic acids, acetoin, butanediol, fatty acids and amino acids important for the generation of compounds that contribute to the sensorial quality of pozol, were found.
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http://dx.doi.org/10.3389/fnut.2021.714814DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8417691PMC
August 2021

Evaluation of endosulfan degradation capacity by six pure strains isolated from a horticulture soil.

Folia Microbiol (Praha) 2021 Dec 14;66(6):973-981. Epub 2021 Jul 14.

Depto. de Procesos y Tecnología, Universidad Autónoma Metropolitana-Cuajimalpa. Av. Vasco de Quiroga 4871, Col. Santa Fe. C.P. 05348, México City, Mexico.

Endosulfan is an organochlorine pesticide included in the Stockholm Convention for Persistent Organic Compounds. The utilization of endosulfan as the sole source of carbon and its mineralization was evaluated using pure strains of Bacillus subtilis, Bacillus pseudomycoides, Peribacillus simplex, Enterobacter cloacae, Achromobacter spanius, and Pseudomonas putida, isolated from soil with historical pesticide use. The consumption of the α isomer of endosulfan by five of the six strains studied was higher than 95%, while B. subtilis degraded only 76% of the initial concentration (14 mg/L). On the other hand, the degradation of the β isomer was approximately 86% of the initial concentration (6 mg/L) by B. subtilis, P. simplex, and B. pseudomycoides and 95% by P. putida, E. cloacae, and A. spanius. The ability of A. spanius, P. simplex, and B. pseudomycoides to degrade endosulfan has not been previously reported. The production of endosulfan lactone by the Bacillus strains, as well as A. spanius and P. putida, indicated that endosulfan was degraded by the hydrolytic pathway.
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http://dx.doi.org/10.1007/s12223-021-00899-5DOI Listing
December 2021

Antioxidant and antimicrobial material by grafting of L-arginine onto enzymatic poly(gallic acid).

Mater Sci Eng C Mater Biol Appl 2021 Feb 22;121:111650. Epub 2020 Oct 22.

Facultad de Química, Departamento de Alimentos y Biotecnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México 04510, Mexico. Electronic address:

Microwave-mediated grafting of L-Arg onto naturally derived and stable multiradical poly(gallic acid) (PGAL) in aqueous media has been successfully achieved. This polymeric material has no adverse effect in human cells as there is no hemolytic activity upon MTT and Neutral Red assays. The analytical and computational characterization studies carried out in this study describe a helical molecular structure with random incorporation of L-Arginine pendant groups from PGAL's backbone. The antioxidant properties of the precursor polymer are preserved as proved by the elimination of stable DPPH and hydroxyl radical scavenging, as well as the FRAP and ORAC assays. Regarding the latter, the oxygen radical inhibition is enhanced compared to PGAL, which is attributed to the guanidyl moieties. PGAL-g-L-Arg displays antimicrobial activity against Gram (+) Listeria monocytogenes and Staphylococcus aureus strains with a MIC of 0.8 g/L and a bacteriostatic effect against Gram (-) Escherichia coli. Additionally, scanning electron and confocal fluorescence microscopies as well as crystal violet colorimetric assay demonstrate that the mechanism involved in the bacterial inhibition is related to the formation of porous channels on the membrane, which is discussed according to the helical secondary structure of the polymer and the amino acid guanidyl moieties interacting to bacterial membranes.
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http://dx.doi.org/10.1016/j.msec.2020.111650DOI Listing
February 2021

Nitrogen Fixation in Pozol, a Traditional Fermented Beverage.

Appl Environ Microbiol 2020 08 3;86(16). Epub 2020 Aug 3.

Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico

Traditional fermentations have been widely studied from the microbiological point of view, but little is known from the functional perspective. In this work, nitrogen fixation by free-living nitrogen-fixing bacteria was conclusively demonstrated in pozol, a traditional Mayan beverage prepared with nixtamalized and fermented maize dough. Three aspects of nitrogen fixation were investigated to ensure that fixation actually happens in the dough: (i) the detection of acetylene reduction activity directly in the substrate, (ii) the presence of potential diazotrophs, and (iii) an increase in acetylene reduction by inoculation with one of the microorganisms isolated from the dough. Three genera were identified by sequencing the 16S rRNA and genes as , , and , and their ability to fix nitrogen was confirmed. Nitrogen-fixing bacteria are found in different niches, as symbionts in plants, in the intestinal microbiome of several insects, and as free-living microorganisms. Their use in agriculture for plant growth promotion via biological nitrogen fixation has been extensively reported. This work demonstrates the ecological and functional importance that these bacteria can have in food fermentations, reevaluating the presence of these genera as an element that enriches the nutritional value of the dough.
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http://dx.doi.org/10.1128/AEM.00588-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7414965PMC
August 2020

Tolerance to acid and alkali by Streptococcus infantarius subsp. infantarius strain 25124 isolated from fermented nixtamal dough: Pozol. Studies in APT broth.

Food Microbiol 2020 Sep 12;90:103458. Epub 2020 Feb 12.

Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Coyoacán, C.P., 04510, Mexico City, Mexico. Electronic address:

Pozol is a beverage prepared with maize dough made after boiling the kernels in limewater. This pretreatment could act as a selective force that shapes the starter microbiota, with microorganisms able to survive the fermentation. Since Streptococcus infantarius subsp. infantarius (Sii) dominates in pozol, we evaluated the effect of acid and alkali stresses on strain Sii-25124 in commercial APT broth as a first attempt to assess its adaptation capacity. Results suggest that Sii-25124 has adaptative advantages to pH changes that possibly contribute to its persistence even after the acidification of the dough. Its cardinal pH values were 4.0 and 11.0, with an optimum between 6.6 and 8.0. It showed alkali tolerance unlike other pozol Sii strains. Adaptation at pH 4.0, 10.0 and 11.0, compared with non-adapted cells, induced acid tolerance enhancing survival at pH 3.6 (P < 0.05); a 2 min heat shock at 62 °C induced alkali tolerance response enhancing survival at pH 10.5 (P < 0.05). The up-regulation of dnaK, groEL, ptsG and atpB was observed during 5 h of exposition at pH 3.6, 4.0 and 10.0, showing similar expression rates after induction by acid shock or alkaline stress. Changes of atpB were more evident having almost five-fold induction during long-term stress.
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http://dx.doi.org/10.1016/j.fm.2020.103458DOI Listing
September 2020

Lactic Acid Fermentation of Arabinoxylan From by ssp. 25124 Isolated From Pozol.

Front Microbiol 2018 18;9:3061. Epub 2018 Dec 18.

Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Mexico City, Mexico.

ssp. 25124 (25124) is a lactic acid bacterium (LAB) isolated from , a refreshing beverage prepared by suspending fermented (a thermal and alkali-treated maize dough) in water. Although s are the predominant strains in fermented doughs, such as sourdoughs, and non-nixtamalized fermented maize foods, the microbiota is markedly different. This may be the result of the nixtamalization process, which could act as a selective force of some strains. 25124 has been reported as the main amylolytic LAB in pozol; starch is the primary carbon source on since monosaccharides and disaccharides are lost during nixtamalization; however, non-amylolytic LAB counts are higher than amylolytic LAB in after 24-h fermentation suggesting that another carbon source is being used by the former bacteria. Hemicellulose (arabinoxylan in maize) becomes available via nixtamalization and is subsequently metabolized by LAB. The aim of this work was to determine whether this bacterium is able to use arabinoxylan as the only carbon source in a defined medium containing arabinoxylan extracted from either (wash water produced during preparation), or beechwood xylan. Xylanase activity in the presence of arabinoxylan (135.8 ± 48.7 IU/mg protein) was higher than that of beechwood (62.5 ± 19.8 IU/mg protein). Other enzymatic activities, such as arabinofuranosidase and acetyl esterase, were also detected, suggesting the adaptation of the bacterium studied to dough. It was concluded that 25124 isolated from was able to use arabinoxylans, which are present in nixtamal dough, so fermentation does not depend exclusively on free sugars and starch.
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http://dx.doi.org/10.3389/fmicb.2018.03061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305286PMC
December 2018

Omics in traditional vegetable fermented foods and beverages.

Crit Rev Food Sci Nutr 2020 22;60(5):791-809. Epub 2018 Dec 22.

Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad de México, México.

For a long time, food microbiota has been studied using traditional microbiological techniques. With the arrival of molecular or culture-independent techniques, a strong understanding of microbiota dynamics has been achieved. However, analyzing the functional role of microbial communities is not an easy task. The application of omics sciences to the study of fermented foods would provide the metabolic and functional understanding of the microbial communities and their impact on the fermented product, including the molecules that define its aroma and flavor, as well as its nutritional properties. Until now, most omics studies have focused on commercial fermented products, such as cheese, wine, bread and beer, but traditional fermented foods have been neglected. Therefore, the information that allows to relate the present microbiota in the food and its properties remains limited. In this review, reports on the applications of omics in the study of traditional fermented foods and beverages are reviewed to propose new ways to analyze the fermentation phenomena.
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http://dx.doi.org/10.1080/10408398.2018.1551189DOI Listing
February 2020

Predominant Yeasts During Artisanal Mezcal Fermentation and Their Capacity to Ferment Maguey Juice.

Front Microbiol 2018 6;9:2900. Epub 2018 Dec 6.

Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico.

Artisanal mezcal is produced by the natural fermentation of maguey juice, which frequently results in a process that becomes stuck or is sluggish. Using selected indigenous starter inoculums of and non- yeasts is considered beneficial in overcoming these problems and thereby preserving the essence of the artisanal process. In this work, three hundred and four yeast isolates were recovered from 17 distilleries and then grouped by the ARDRA analysis, their restriction profiles were clustered in 15 groups. Four of them included 90% of all isolates, and these were identified using the sequence of the D1/D2 domain of the large-subunit rDNA. , and were detected as predominant species. Both species belonging to the genus were detected in 88% of the distilleries, followed by (70%) and (50%). In order to evaluate the fermentative capacity, one strain of each species was assessed in a pure and mixed culture in two culture media, filtered maguey juice (MJ) and maguey juice including its bagasse (MJB). Findings demonstrated that non- yeast presented better growth than that of . . PA16 was more efficient for ethanol production than DI14. It produced 32 g/L of ethanol with a yield of 0.47 g/g and efficient of 90%. While, produced more ethyl acetate (280 mg/L) than the others species. All fermentations were characterized by the presence of isobutyl and isoamyl alcohol. The presence of in a mixed culture, improved the ethanol production and volatile compounds increased using co-cultures.
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http://dx.doi.org/10.3389/fmicb.2018.02900DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6291486PMC
December 2018

Draft Genome Sequence of CW28 Isolated from Pozol, a Pre-Hispanic Fermented Corn Beverage.

Genome Announc 2017 Nov 30;5(48). Epub 2017 Nov 30.

Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico

CW28 was isolated from pozol, a Mayan fermented corn beverage. This strain produces a cell-associated inulosucrase, the first described in bacteria. Its draft genome sequence, announced here, has an estimated size of 1.98 Mb and harbors 1,915 coding genes, 12 rRNAs, 68 tRNAs, 17 putative pseudogenes, and 1 putative phage.
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http://dx.doi.org/10.1128/genomeA.01283-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5722060PMC
November 2017

Diversity and dynamics of lactic acid bacteria in Atole agrio, a traditional maize-based fermented beverage from South-Eastern Mexico, analysed by high throughput sequencing and culturing.

Antonie Van Leeuwenhoek 2018 Mar 22;111(3):385-399. Epub 2017 Oct 22.

Departamento de Microbiología y Ecología, Universitat de València (UVEG), Av. Dr. Moliner, 50, 46100, Burjassot, Valencia, Spain.

The purpose of this work was to analyse the diversity and dynamics of lactic acid bacteria (LAB) throughout the fermentation process in Atole agrio, a traditional maize based food of Mexican origin. Samples of different fermentation times were analysed using culture-dependent and -independent approaches. Identification of LAB isolates revealed the presence of members of the genera Pediococcus, Weissella, Lactobacillus, Leuconostoc and Lactococcus, and the predominance of Pediococcus pentosaceus and Weissella confusa in liquid and solid batches, respectively. High-throughput sequencing (HTS) of the 16S rRNA gene confirmed the predominance of Lactobacillaceae and Leuconostocaceae at the beginning of the process. In liquid fermentation Acetobacteraceae dominate after 4 h as pH decreased. In contrast, Leuconostocaceae dominated the solid fermentation except at 12 h that were overgrown by Acetobacteraceae. Regarding LAB genera, Lactobacillus dominated the liquid fermentation except at 12 h when Weissella, Lactococcus and Streptococcus were the most abundant. In solid fermentation Weissella predominated all through the process. HTS determined that Lactobacillus plantarum and W. confusa dominated in the liquid and solid batches, respectively. Two oligotypes have been identified for L. plantarum and W. confusa populations, differing in a single nucleotide position each. Only one of the oligotypes was detected among the isolates obtained from each species, the biological significance of which remains unclear.
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http://dx.doi.org/10.1007/s10482-017-0960-1DOI Listing
March 2018

In Vitro Evaluation of the Probiotic and Safety Properties of Bacteriocinogenic and Non-Bacteriocinogenic Lactic Acid Bacteria from the Intestines of Nile Tilapia and Common Carp for Their Use as Probiotics in Aquaculture.

Probiotics Antimicrob Proteins 2018 03;10(1):98-109

Departamento de Biotecnología, Universidad Autónoma Metropolitana-Iztapalapa (UAM-I), Av. San Rafael Atlixco 186, 09340, Mexico, Distrito Federal, Mexico.

In this study, seven bacteriocinogenic and non-bacteriocinogenic LAB strains previously isolated from the intestines of Nile tilapia and common carp and that showed potent antibacterial activity against host-derived and non-host-derived fish pathogens were assayed for their probiotic and safety properties so as to select promising candidates for in vivo application as probiotic in aquaculture. All the strains were investigated for acid and bile tolerances, transit tolerance in simulated gastrointestinal conditions, for cell surface characteristics including hydrophobicity, co-aggregation and auto-aggregation, and for bile salt hydrolase activity. Moreover, haemolytic, gelatinase and biogenic amine-producing abilities were investigated for safety assessment. The strains were found to be tolerant at low pH (two strains at pH 2.0 and all the strains at pH 3.0). All of them could also survive in the presence of bile salts (0.3% oxgall) and in simulated gastric and intestinal juices conditions. Besides, three of them were found to harbour the gtf gene involved in pH and bile salt survival. The strains also showed remarkable cell surface characteristics, and 57.14% exhibited the ability to deconjugate bile salts. When assayed for their safety properties, the strains prove to be free from haemolytic activity, gelatinase activity and they could neither produce biogenic amines nor harbour the hdc gene. They did not also show antibiotic resistance, thus confirming to be safe for application as probiotics. Among them, Lactobacillus brevis 1BT and Lactobacillus plantarum 1KMT exhibited the best probiotic potentials, making them the most promising candidates.
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http://dx.doi.org/10.1007/s12602-017-9312-8DOI Listing
March 2018

Quantitative analyses of the bacterial microbiota of rearing environment, tilapia and common carp cultured in earthen ponds and inhibitory activity of its lactic acid bacteria on fish spoilage and pathogenic bacteria.

World J Microbiol Biotechnol 2017 Feb 7;33(2):32. Epub 2017 Jan 7.

Departamento de Biotecnología, Universidad Autónoma Metropolitana-Iztapalapa (UAM-I), Av. San Rafael Atlixco 186, 09340, Mexico, Distrito Federal, Mexico.

The present study aimed to evaluate the bacterial load of water, Nile Tilapia and common Carp intestines from earthen ponds, isolate lactic acid bacteria (LAB) and assess their antimicrobial activity against fish spoilage and pathogenic bacteria. Following enumeration and isolation of microorganisms the antimicrobial activity of the LAB isolates was evaluated. Taxonomic identification of selected antagonistic LAB strains was assessed, followed by partial characterisation of their antimicrobial metabolites. Results showed that high counts (>4 log c.f.u ml or 8 log c.f.u g) of total aerobic bacteria were recorded in pond waters and fish intestines. The microbiota were also found to be dominated by Salmonella spp., Vibrio spp., Staphylococcus spp. and Escherichia coli. LAB isolates (5.60%) exhibited potent direct and extracellular antimicrobial activity against the host-derived and non host-derived spoilage and pathogenic bacteria. These antagonistic isolates were identified and Lactococcus lactis subsp. lactis was found as the predominant (42.85%) specie. The strains displayed the ability to produce lactic, acetic, butyric, propionic and valeric acids. Bacteriocin-like inhibitory substances with activity against Gram-positive and Gram-negative (Vibrio spp. and Pseudomonas aeruginosa) bacteria were produced by three L. lactis subsp. lactis strains. In this study, the LAB from the microbiota of fish and pond water showed potent antimicrobial activity against fish spoilage or pathogenic bacteria from the same host or ecological niche. The studied Cameroonian aquatic niche is an ideal source of antagonistic LAB that could be appropriate as new fish biopreservatives or disease control agents in aquaculture under tropical conditions in particular or worldwide in general.
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http://dx.doi.org/10.1007/s11274-016-2197-yDOI Listing
February 2017

Effect of postharvest UV-C treatment on the bacterial diversity of Ataulfo mangoes by PCR-DGGE, survival of E. coli and antimicrobial activity.

Front Microbiol 2013 5;4:134. Epub 2013 Jun 5.

Lab 324, Conjunto E, Departamento de Alimentos y Biotecnología, Facultad de Química, Universidad Nacional Autónoma de México Mexico City, Mexico.

Since Mexico is the second largest exporter of mangoes, its safety assurance is essential. Research in microbial ecology and knowledge of complex interactions among microbes must be better understood to achieve maximal control of pathogens. Therefore, we investigated the effect of UV-C treatments on bacterial diversity of the Ataulfo mangoes surface using PCR-DGGE analysis of variable region V3 of 16S rRNA genes, and the survival of E. coli, by plate counting. The UV-C irradiation reduced the microbial load on the surface of mangoes immediately after treatment and the structure of bacterial communities was modified during storage. We identified the key members of the bacterial communities on the surface of fruits, predominating Enterobacter genus. Genera as Lactococcus and Pantoea were only detected on the surface of non-treated (control) mangoes. This could indicate that these genera were affected by the UV-C treatment. On the other hand, the treatment did not have a significant effect on survival of E. coli. However, genera that have been recognized as antagonists against foodborne pathogens were identified in the bands patterns. Also, phenolic compounds were determined by HPLC and antimicrobial activity was assayed according to the agar diffusion method. The main phenolic compounds were chlorogenic, gallic, and caffeic acids. Mango peel methanol extracts (UV-C treated and control mangoes) showed antimicrobial activity against strains previously isolated from mango, detecting significant differences (P < 0.05) among treated and control mangoes after 4 and 12 days of storage. Ps. fluorescens and Ps. stutszeri were the most sensitive.
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http://dx.doi.org/10.3389/fmicb.2013.00134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3673002PMC
June 2013

Chemical and nutritional composition of tejate, a traditional maize and cacao beverage from the Central Valleys of Oaxaca, Mexico.

Plant Foods Hum Nutr 2012 Jun;67(2):148-55

Departamento de Farmacía, Facultad de Química, Laboratorio 111, Universidad Nacional Autónoma de México, 04510 México, DF, México.

Foam-topped cacao and maize beverages have a long history in Mesoamerica. Tejate is such a beverage found primarily in the Zapotec region of the Central Valleys of Oaxaca, Mexico. Historically tejate has been ceremonially important but also as an essential staple, especially during periods of hard fieldwork. However, the nutritional contribution of traditional foods such as tejate has not been investigated. We analyzed tejate samples from three Central Valley communities, vendors in urban Oaxaca markets and one migrant vendor in California, USA for their proximate composition, amino acid content and scores, and mineral and methylxanthine content. Nutritional and chemical variation exists among tejate recipes, however, the beverage is a source of energy, fat, methylxanthines, K, Fe and other minerals although their availability due to presence of phytates remains to be determined. Tejate is a source of protein comparable to an equal serving size of tortillas, with protein quality similarly limited in both. Tejate provides the nutritional benefits of maize, and some additional ones, in a form appealing during hot periods of intense work, and year round because of its cultural significance. Its substitution by sodas and other high glycemic beverages may have negative nutritional, health and cultural consequences.
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http://dx.doi.org/10.1007/s11130-012-0281-5DOI Listing
June 2012

Microbial ecology, in foods and at the intestine.

Curr Opin Biotechnol 2010 Apr 19;21(2):123-4. Epub 2010 Apr 19.

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http://dx.doi.org/10.1016/j.copbio.2010.03.018DOI Listing
April 2010

Interaction of shockwaves with infected kidney stones: is there a bactericidal effect?

J Endourol 2008 Aug;22(8):1629-37

Faculty of Sciences , Universidad Nacional Autónoma de México, México D.F., México.

Background And Purpose: Many calculi contain bacteria, which can remain active inside kidney stones and cause infection after lithotripsy. Reduction in renal infections after extracorporeal shockwave lithotripsy has been observed; however, results are controversial, and no information on the effect of shockwaves on bacteria inside kidney stones has been reported. The purpose of this research was to study whether bacteria inside kidney stones can be inactivated by shockwaves.

Materials And Methods: A series of infected artificial kidney stones were exposed in vitro to either 90 or 400 shockwaves using a research electrohydraulic or a commercial piezoelectric lithotripter. Two types of stones (soft and hard) were manufactured by mixing gypsum cement and Vel-mix-stone with water. Half of the stones were inoculated with Salmonella typhimurium. The suspension containing stone powder and bacteria was inoculated on agar plates and incubated. Bactericidal action was defined as the logarithmic viability reduction.

Results: About 95% of the bacteria were inactivated with 400 shockwaves using the electrohydraulic lithotripter; however, most of the damage was associated with the electromagnetic emission (ultraviolet radiation and visible light) generated at the spark gap. After 2730 shockwaves to stones placed inside a black polypropylene bag, about 29% and 14% of all bacteria were inactivated with the piezoelectric and the electrohydraulic lithotripter, respectively. In this case, the electromagnetic radiation was blocked by the black bag.

Conclusions: Bacteria inactivation is possible by in vitro shockwave application; however, according to our results, no significant bactericidal effect is expected during extracorporeal shockwave lithotripsy.
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http://dx.doi.org/10.1089/end.2007.0389DOI Listing
August 2008

Characterization of the polyurethanolytic activity of two Alicycliphilus sp. strains able to degrade polyurethane and N-methylpyrrolidone.

Appl Environ Microbiol 2007 Oct 10;73(19):6214-23. Epub 2007 Aug 10.

Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, 04510 México, D.F. México.

Two bacterial strains (BQ1 and BQ8) were isolated from decomposed soft foam. These were selected for their capacity to grow in a minimal medium (MM) supplemented with a commercial surface-coating polyurethane (PU) (Hydroform) as the carbon source (MM-PUh). Both bacterial strains were identified as Alicycliphilus sp. by comparative 16S rRNA gene sequence analysis. Growth in MM-PUh showed hyperbolic behavior, with BQ1 producing higher maximum growth (17.8 +/- 0.6 mg.ml(-1)) than BQ8 (14.0 +/- 0.6 mg.ml(-1)) after 100 h of culture. Nuclear magnetic resonance, Fourier transform infrared (IR) spectroscopy, and gas chromatography-mass spectrometry analyses of Hydroform showed that it was a polyester PU type which also contained N-methylpyrrolidone (NMP) as an additive. Alicycliphilus sp. utilizes NMP during the first stage of growth and was able to use it as the sole carbon and nitrogen source, with calculated K(s) values of about 8 mg.ml(-1). Enzymatic activities related to PU degradation (esterase, protease, and urease activities) were tested by using differential media and activity assays in cell-free supernatants of bacterial cultures in MM-PUh. Induction of esterase activity in inoculated MM-PUh, but not that of protease or urease activities, was observed at 12 h of culture. Esterase activity reached its maximum at 18 h and was maintained at 50% of its maximal activity until the end of the analysis (120 h). The capacity of Alicycliphilus sp. to degrade PU was demonstrated by changes in the PU IR spectrum and by the numerous holes produced in solid PU observed by scanning electron microscopy after bacterial culture. Changes in the PU IR spectra indicate that an esterase activity is involved in PU degradation.
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http://dx.doi.org/10.1128/AEM.01230-07DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075003PMC
October 2007

Survival to different acid challenges and outer membrane protein profiles of pathogenic Escherichia coli strains isolated from pozol, a Mexican typical maize fermented food.

Int J Food Microbiol 2005 Dec 16;105(3):357-67. Epub 2005 Sep 16.

Universidad Autónoma Metropolitana Xochimilco-Iztapalapa, México D.F., Mexico.

In this study, the acid resistance and the changes in outer membrane protein (Omps) profiles of Escherichia coli strains isolated from pozol, an acid-fermented maize beverage consumed in Southeastern Mexico, were determined. Results showed that adaptation to acid by these E. coli strains significantly enhances their survival in acid conditions. Changes in Omp profiles were found in non-adapted acid challenged cells compared with non-challenged cells that had not been adapted to acid. Challenged adapted cells showed no significant changes in these profiles when compared with the acid adapted non-challenged strains. N-terminal sequences of some of the Omps were determined. The intensity of the main porins OmpC and OmpA was lower in the acid challenged strains, than in the non-challenged ones. The OmpF porin was identified in non-challenged K12 strain, but did not appear in adapted or non-adapted pozol strains nor in E. coli O157:H7. A protein band with an approximate molecular mass of 22 kDa corresponds to OmpW and its expression decreased in pozol strains challenged with HCl and lactic acid. OmpX was one of the main proteins expressed when strains were acid challenged with organic acids. Seventy out of seventy-three E. coli strains isolated from pozol in a previous work [Sainz, T., Wacher, C., Espinoza, J., Centurion, D., Navarro, A., Molina, J., Cravioto, A., Eslava, C., 2001. Survival and characterization of Escherichia coli strains in a typical Mexican acid-fermented food. International Journal of Food Microbiology 71, 169-176] carry this gene and belong to a reported pathogenic class of E. coli strains, or have virulence factors or survived at pH values less than 4.8. We suggest this protein could be involved in survival to stress conditions.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2005.04.017DOI Listing
December 2005

Activity of the enzymes involved in the synthesis of exopolysaccharide precursors in an overproducing mutant ropy strain of Streptococcus thermophilus.

FEMS Microbiol Lett 2002 Apr;209(2):289-93

Departamento de Alimentos y Biotecnología, Lab. 312, Conjunto E, Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, D.F. 04510, Mexico.

The activities of some enzymes belonging to the Leloir pathway, phosphoglucomutase, UDP-glucose pyrophosphorylase, UDP-galactose 4-epimerase and galactose 1-P uridyl transferase, were studied in a wild ropy, a non-ropy and an overproducing mutant ropy strain of Streptococcus thermophilus. These activities were assayed over successive culture transfers along with exocellular polysaccharide (EPS) production. The overproducing mutant ropy strain showed increments in polysaccharide production over successive culture transfers, as opposed to reductions in production by the wild ropy strain. The observed variations among strains in the enzyme activities that were analysed in relation to EPS production suggest their involvement in the synthesis of sugar-nucleotide EPS precursors.
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http://dx.doi.org/10.1111/j.1574-6968.2002.tb11146.xDOI Listing
April 2002
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