Bacteria Lactobacillus Fermentum Research Articles

Dense tracking of the dynamics of the microbial community and chemicals constituents in spontaneous wheat sourdough during two months of backslopping

Wheat sourdough is a common traditional fermented food that is produced worldwide. However, product quality of spontaneous sourdough is not easy to control because it depends on natural fermentation and backslopping, about which little is known, notably after ten backslopping steps. To this end, we tracked the spontaneous fermentation of three sourdoughs made from wheat flours during 32 backslopping steps for 60 days. At 24 time points, the microbial community was analyzed by both culture-dependent and culture-independent methods and its chemical constituents were assessed. Dynamic changes were observed in the microbial community, which showed a common succession pattern among the three sourdoughs at the bacterial family level and differences at the species level. The bacterial communities evolved through three phases that were driven by different groups of lactic acid bacteria (LAB) species. The dynamism among the metabolites also differed, depending on the species composition of the LAB and yeast communities. In one sourdough, the growth of Saccharomyces cerevisiae was detected along with a concentration of increased ethanol, while in the other two sourdoughs, Wickerhamomyces anomalus was detected without ethanol production. Regarding the LAB communities, two sourdoughs were eventually co-dominated by Lactobacillus plantarum and L. brevis, while the other sourdough was eventually dominated solely by the heterolactic fermentative bacterium Lactobacillus fermentum, and ethanol was produced at the same level as lactic acid. Further research is needed to determine the bacterial and yeast species involved in the fermentation of sourdough, to help improve the design and quality control of the final product.

Effect of plating and incubation conditions on the detection of lactic acid bacteria after high hydrostatic pressure treatment

ABSTRACTLactic acid bacteria (Leuconostoc mesenteroides, Enterococcus faecalis, and Lactobacillus fermentum) were subjected to high hydrostatic pressures (HHPs) of 400 and 600 MPa at 25°C for 10 min in phosphate-buffered saline. Differential plating methods were applied to evaluate HHP-treated cell populations, assuming that healthy and injured cells during plate incubation survived maximum and minimal stress, respectively. The stress was altered by using several selective media in combination with aerobic or anaerobic incubation at 25°C or 30°C. E. faecalis was detectable after 600 MPa treatment while L. mesenteroides and L. fermentum were nondetectable. Specific combinations of incubation conditions were suggested to determine maximum and minimum viable counts of L. mesenteroides and E. faecalis. The difference between the maximum and minimum counts can be used to evaluate HHP-injured population with reduced risks to overestimate healthy and/or underestimate HHP-injured cells.

Survival and stability of Lactobacillus fermentum and Wickerhamomyces anomalus strains upon lyophilisation with different cryoprotectant agents

The stability of microorganisms along the time is important for allowing their industrial use as starter agents, improving fermentation processes. This study aimed to evaluate the survival and maintenance of the cell viability of the lactic acid bacteria Lactobacillus fermentum IAL 4541 and the yeast Wickerhamomyces anomalus IAL 4533, both isolated from wheat sourdough, after lyophilisation with different cryoprotectant and storage at room temperature along a year. Treatments involved adding control solution (S1 = 0.1% peptone water), and four cryoprotectant solutions S2 (10% sucrose), S3 (5% trehalose), S4 (10% skim milk powder) and S5 (10% skim milk powder plus 5% sodium glutamate) to the microbial cells previously of freeze drying processing. To verify the effect of lyophilisation on the number of microbial cells recovered, microbiological analyses were performed and cell viability was calculated before and after lyophilisation and regularly during a storage period of 365 days at room temperature. Viability after freeze-drying was influenced by the cryoprotectant agent employed, as well the microbial stability conferred along the storage. Differences on the microorganism response to some protectors were observed between the lactic acid bacteria and the yeast evaluated. W. anomalus was more affected by absence of cryoprotectant (S1) during freeze drying processing, but this microorganism was more stable than L. fermentum along the storage without the presence of protectant agents. For L. fermentum, S5 was the best protectant, allowing the recovering of 100% of the bacterial cells after lyophilisation and 87% of cell viability was observed after one year storage, followed by S4 (96 and 74%, respectively). S4 and S5 were the best protectant to W. anomalus (viability >80% after 1 year), but no increase in the yeast cell viability was conferred by addition of glutamate (S5) to skim milk. After 1 year of storage, trehalose was much more effective on protection of the yeast than bacteria (72% and 7% of viability, respectively). S2 was the less protectant agent among the tested, and their effectiveness was higher in L. fermentum (allowing 14% of cell recovering up to 120 days of storage) if compared to W. anomalus (25% of viability until 90 days of storage). Our results demonstrate that freeze-drying is a realistic technology for the stability and maintenance of the potential sourdough starter L. fermentum and W. anomalus for long time; however, the choice of cryoprotectant will influence the process effectiveness.

Consumption of Probiotic Lactobacillus fermentum MTCC: 5898-Fermented Milk Attenuates Dyslipidemia, Oxidative Stress, and Inflammation in Male Rats Fed on Cholesterol-Enriched Diet.

There is a growing and alarming prevalence that increased serum cholesterol is closely related to increased cardiovascular disease risk. Probiotic consumption could be a safe and natural strategy to combat. Therefore, we sought to examine the cholesterol-lowering potential of co-supplementation of probiotic bacteria Lactobacillus fermentum MTCC: 5898-fermented buffalo milk (2.5% fat) in rats fed cholesterol-enriched diet. Male Wistar rats were divided into three groups on the basis of feed, viz. group 1, fed standard diet (SD); group 2, fed cholesterol-enriched diet (CED); and group 3, fed cholesterol-enriched diet along with L. fermentum MTCC: 5898-fermented milk (CED+LF) for 90days. At the endpoint, significantly higher levels of serum total cholesterol, low-density lipoprotein cholesterol, triacylglycerols, very low density lipoprotein cholesterol, atherogenic index, coronary artery risk index, hepatic lipids, lipid peroxidation, and mRNA expression of inflammatory cytokines (TNF-α and IL-6) in the liver while significantly lower levels of serum high-density lipoprotein cholesterol and anti-oxidative enzyme activities, catalase, superoxide dismutase, and glutathione peroxidase in the liver and kidney were observed in the CED group compared to the SD group. Compared to the CED group, these adverse physiological alterations were found significantly improved in the CED+LF group. Hence, this study proposes that L. fermentum MTCC: 5898 is a potential probiotic bacteria that can be consumed to tackle hypercholesterolemia. Graphical Abstract ᅟ.

Complete and Annotated Genome Sequence of the Sourdough Lactic Acid Bacterium Lactobacillus fermentum IMDO 130101.

ABSTRACTLactobacillus fermentum is a species of lactic acid bacteria that is frequently found in sourdough, a fermented flour-water mixture used in the production of bread and other baked goods. Here, we present the complete genome sequence of L. fermentum IMDO 130101, a candidate sourdough starter culture strain isolated from a backslopped rye sourdough.

Bacteria-Carried Iron Oxide Nanoparticles for Treatment of Anemia.

The efficiency of maghemite nanoparticles for the treatment of anemia was sensibly higher when nanoparticles were incorporated onto the probiotic bacterium Lactobacillus fermentum (MNP-bacteria) than when administrated as uncoated nanoparticles (MNP). Plasma iron and hemoglobin, intestine expression of divalent metal transporter 1 (DMT1) and duodenal Cytochrome b (DcytB), as well as hepatic expression of the hormone hepcidin were fully restored to healthy levels after administration of MNP-bacteria but not of MNP. A magnetic study on biodistribution and biodegradation showed accumulation of maghemite nanoparticles in intestine lumen when MNP-bacteria were administrated. In contrast, MNP barely reached intestine. In vivo MRI studies suggested the internalization of MNP-bacteria into enterocytes, which did not occur with MNP. Transmission electronic microscopy confirmed this internalization. The collective analysis of results point out that L. fermentum is an excellent carrier to overcome the stomach medium and drive maghemite nanoparticles to intestine, where iron absorption occurs. Due the probiotic ability to adhere to the gut wall, MNP-bacteria internalize into the enterocyte, where maghemite nanoparticles are delivered, providing an adequate iron level into enterocyte. This paper advances a new route for effective iron absorption in the treatment of anemia.

Unravelling the contribution of lactic acid bacteria and acetic acid bacteria to cocoa fermentation using inoculated organisms

Cocoa beans (Theobroma cacao L.) are the raw material for chocolate production. Fermentation of the bean pulp by microorganisms is essential for developing the precursors of chocolate flavour. Currently, the cocoa fermentation is still conducted by an uncontrolled traditional process via a consortium of indigenous species of yeasts, lactic acid bacteria and acetic acid bacteria. Although the essential contribution of yeasts to the production of good quality beans and, typical chocolate character is generally agreed, the roles of lactic acid bacteria and acetic acid bacteria are less certain. The objective of this study was to investigate the contribution of LAB and AAB in cocoa bean fermentation by conducting small scale laboratory fermentations under aseptic conditions, inoculated with different groups of microorganisms previously isolated from spontaneous cocoa fermentations. The inoculation protocols were: (1) four yeasts Hanseniaspora guilliermondii, Pichia kudriavzevii, Kluyveromyces marxianus and Saccharomyces cerevisiae; (2) four yeasts plus the lactic acid bacteria Lactobacillus plantarum and Lactobacillus fermentum; (3) four yeasts plus the acetic acid bacteria Acetobacter pasteurianus and Gluconobacter frateuri and (4) four yeasts plus two lactic acid bacteria and two acetic acid bacteria. Only the inoculated species were detected in the microbiota of their respective fermentations. Beans from the inoculated fermentations showed no significant differences in colour, shell weights and concentrations of residual sugars, alcohols and esters (p>0.05), but they were slightly different in contents of lactic acid and acetic acid (p<0.05). All beans were fully brown and free of mould. Residual sugar levels were less than 2.6 mg/g while the shell contents and ethanol were in the range of 11–13.4% and 4.8–7 mg/g, respectively. Beans fermented in the presence of LAB contained higher levels of lactic acid (0.6-1.2 mg/g) whereas higher concentrations of acetic acid (1.8–2.2 mg/g) were detected in beans inoculated with AAB.Triangle and hedonic sensory evaluations of chocolates prepared from beans taken from the three fermentations showed no significant differences (p > 0.05). It was concluded that the growth of lactic acid bacteria and acetic acid bacteria may not be essential for the fermentation of cocoa beans.

Interaction of Saccharomyces cerevisiae-Lactobacillus fermentum-Dekkera bruxellensis and feedstock on fuel ethanol fermentation.

The alcoholic fermentation for fuel ethanol production in Brazil occurs in the presence of several microorganisms present with the starter strain of Saccharomyces cerevisiae in sugarcane musts. It is expected that a multitude of microbial interactions may exist and impact on the fermentation yield. The yeast Dekkera bruxellensis and the bacterium Lactobacillus fermentum are important and frequent contaminants of industrial processes, although reports on the effects of both microorganisms simultaneously in ethanolic fermentation are scarce. The aim of this work was to determine the effects and interactions of both contaminants on the ethanolic fermentation carried out by the industrial yeast S. cerevisiae PE-2 in two different feedstocks (sugarcane juice and molasses) by running multiple batch fermentations with the starter yeast in pure or co-cultures with D. bruxellensis and/or L. fermentum. The fermentations contaminated with D. bruxellensis or L. fermentum or both together resulted in a lower average yield of ethanol, but it was higher in molasses than that of sugarcane juice. The decrease in the CFU number of S. cerevisiae was verified only in co-cultures with both D. bruxellensis and L. fermentum concomitant with higher residual sucrose concentration, lower glycerol and organic acid production in spite of a high reduction in the medium pH in both feedstocks. The growth of D. bruxellensis was stimulated in the presence of L. fermentum resulting in a more pronounced effect on the fermentation parameters than the effects of contamination by each microorganism individually.

Padina caulescens and Schizochytrium sp. as Supplemented Feed in the Nursery Production of Penaeus vannamei Post Larvae Reared in Biofloc Systems

The appearance of diverse diseases in cultured shrimp has led to the search for alternative prevention strategies. One of these alternatives is Biofloc technology (BFT). However, this requires further optimization. The objective of this work is to improve this system by adding microalgae (Schizochytrium sp.), probiotic bacteria (Lactobacillus fermentum), and macroalga (Padina caulescens), which in addition to maintaining the quality of water in the Penaeus vannamei culture, improves growth parameters at the maternity stage. We installed an experiment that included six different treatments in culture tanks containing 250 L of seawater each, and 500 shrimp (68 mg) m/3, and evaluated the results for 35 days, in which we gradually decreased the inert-feed to 50-75% and substituted it with 50-25% of P. caulescens. The results showed that, in comparison to the control, survival, and final weight of the shrimps improved and improved further with the use of probiotic bacteria, Schizochytrium sp. and P. caulescens and probiotic bacteria enabled a reduction of 50% of the inert feed. Therefore, we recommended the use of P. caulescens, Schizochytrium sp. (LPU-1), and L. fermentum (T-19) in BFT cultures for P. vannamei.

A novel protein tyrosine phosphatase like phytase from Lactobacillus fermentum NKN51: Cloning, characterization and application in mineral release for food technology applications

A novel protein tyrosine phosphatase like phytase (PTPLP), designated as PhyLf from probiotic bacterium Lactobacillus fermentum NKN51 was identified, cloned, expressed and characterized. The recombinant PhyLf showed specific activity of 174.5 U/mg. PhyLf exhibited strict specificity towards phytate and optimum temperature at 60 °C, pH 5.0 and ionic strength of 100 mM. Km and Kcat of PhyLf for phytate were 0.773 mM and 84.31 s−1, respectively. PhyLf exhibited high resistance against oxidative inactivation. PhyLf shares no homology, sans the active site with reported PTLPs, warranting classification as a new subclass. Dephytinization of durum wheat and finger millet under in vitro gastrointestinal conditions using PhyLf enhanced the bioaccessibility of mineral ions. Probiotic origin, phytate specificity, resistance to oxidative environment and gastric milieu coupled with ability to release micronutrients are unique properties of PhyLf which present a strong case for its use in ameliorating nutritional value of cereals and animal feed.

Ferulic Acid Produced by Lactobacillus fermentum NCIMB 5221 Reduces Symptoms of Metabolic Syndrome in Drosophila melanogaster

Abstract The gut microbiota is an intricate community of thousands of bacterial species living in the gastrointestinal tract critical for vitamin synthesis, mineral absorption, digestion of otherwise indigestible fibers and the extraction of energy from food. Recently, the health of the gut microbiota’s community architecture has become linked to energy-regulatory diseases including metabolic syndrome: a collection of symptoms including hyperglycemia, hypercholesterolemia, high blood pressure, increased abdominal fat and triglyceride levels. However, the mechanism of communication between the gut microbiota and the host energy metabolism remains elusive. The current study shows that ferulic acid (FA) produced by the intrinsic ferulic acid esterase activity of the probiotic bacteria Lactobacillus fermentum NCIMB 5221 (Lf5221) can dose-dependently rescue the phenotypic markers of diet-induced diabetes and obesity in Drosophila melanogaster. In Drosophila exposed to either a high-sugar or high-fat diet, living Lf5221 at 2.5 or 7.5 × 109 CFU/ml media effectively rescued whole-body weight, glucose, trehalose and triglyceride levels. All of the aforementioned effects were lost in heat-inactivated bacteria indicating that a metabolic product is responsible. Likewise, FA at 0.5 mM in the metabolically challenged Drosophila models reared similar effects on the physiological markers while also reducing hyperglycemia in the circulating hemolymph. On the signaling level, the high-sugar diet predictably had an elevated expression of the Drosophila insulin-like peptides 2, 3 and 5 and in the high-fat diet, an increase in fatty acid synthase, acetyl-CoA carboxylase and phosphoenolpyruvate carboxykinase expression. On both diets, Lf5221 and FA rescued gene expression, at different concentrations, to the level of controls. Examining the mechanistic gene expression, both Lf5221 and FA rescued expression of dFOXO and dTOR, but not dAkt indicating that FA produced by Lf5221 is acting on one of the downstream-signaling molecules from the insulin receptor, possibly dTOR: an overall energy regulator in flies and humans alike. The present study for the first time outlines a streamlined mechanism for how the gut microbiota communicates with the host’s energy-regulating metabolism. Proper supplementation with ferulic acid esterase active probiotics such as Lf5221 could potentially prevent or alleviate symptoms of metabolic syndrome and other energy-regulating diseases including diabetes, obesity and neurodegeneration.

Antioxidant potential of a unique LAB culture isolated from Harbin dry sausage: In vitro and in a sausage model

The lactic acid bacteria Pediococcus pentosaceus, Lactobacillus curvatus, Lactobacillus brevis, and Lactobacillus fermentum isolated from Harbin dry sausage were evaluated for their potential antioxidant activity. The in vitro results showed that P. pentosaceus had the strongest H2O2 resistance, radical scavenging activity, reducing power, and inhibition of lipid peroxidation (P<0.05). Additionally, superoxide dismutase and glutathione peroxidase activities in P. pentosaceus were higher than those observed in three other strains (P<0.05). The inoculation of P. pentosaceus in dry sausage significantly decreased the quantities of thiobarbituric acid-reactive substance and carbonyl formation, while it also reduced the sulfhydryl loss in sausages (P<0.05). Furthermore, the lower content of volatile compounds that are related to lipid-oxidation, such as aldehydes, ketones and hydrocarbons, was observed in the P. pentosaceus inoculated sausage (P<0.05). These results demonstrate that P. pentosaceus has the potential to be employed as an antioxidant starter culture in fermented meat products.

The effect of lactic acid bacteria on cocoa bean fermentation

Cocoa beans (Theobroma cacao L.) are the raw material for chocolate production. Fermentation of cocoa pulp by microorganisms is crucial for developing chocolate flavor precursors. Yeasts conduct an alcoholic fermentation within the bean pulp that is essential for the production of good quality beans, giving typical chocolate characters. However, the roles of bacteria such as lactic acid bacteria and acetic acid bacteria in contributing to the quality of cocoa bean and chocolate are not fully understood. Using controlled laboratory fermentations, this study investigated the contribution of lactic acid bacteria to cocoa bean fermentation. Cocoa beans were fermented under conditions where the growth of lactic acid bacteria was restricted by the use of nisin and lysozyme. The resultant microbial ecology, chemistry and chocolate quality of beans from these fermentations were compared with those of indigenous (control) fermentations. The yeasts Hanseniaspora guilliermondii, Pichia kudriavzevii, Kluyveromyces marxianus and Saccharomyces cerevisiae, the lactic acid bacteria Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus fermentum and the acetic acid bacteria Acetobacter pasteurianus and Gluconobacter frateurii were the major species found in control fermentations. In fermentations with the presence of nisin and lysozyme, the same species of yeasts and acetic acid bacteria grew but the growth of lactic acid bacteria was prevented or restricted. These beans underwent characteristic alcoholic fermentation where the utilization of sugars and the production of ethanol, organic acids and volatile compounds in the bean pulp and nibs were similar for beans fermented in the presence of lactic acid bacteria. Lactic acid was produced during both fermentations but more so when lactic acid bacteria grew. Beans fermented in the presence or absence of lactic acid bacteria were fully fermented, had similar shell weights and gave acceptable chocolates with no differences in sensory rankings. It was concluded that lactic acid bacteria may not be necessary for successful cocoa fermentation.

In-Vitro Characterization of the Anti-Cancer Activity of the Probiotic Bacterium Lactobacillus Fermentum NCIMB 5221 and Potential against Colorectal Cancer

Objective: Lactic acid bacteria such as Lactobacillus fermentum, have shown to increase the levels of fecal short chain fatty acids known with its beneficial role in colonic health and were found to produce anti-carcinogenic compounds, suggesting a potential in colorectal cancer prevention. The aim of this study is to characterize the metabolic and anti-cancer features of L. fermentum NCIMB 5221 compared to two other Lactobacillus species. Methods: A free fatty acid (FFA) profile was determined and the anti-proliferative and apoptotic effects of bacterial cell free extracts were investigated. The effect on the growth of colon cancer cells compared to nonneoplastic colon cells was determined. The production of different SCFAs by the probiotic bacteria and the efficacy of their composition were analyzed. Results: The FFA profile of L. fermentum is distinctive FFA profile (~ 368 MAE, 16 h, p < 0.01) compared to L. acidophilus ATCC 314 and L. rhamnosus ATCC 53103. L. fermentum extracts significantly inhibited cancer cell growth up to ~ 40% and induced apoptosis up to ~ 30% in SW-480 colon cancer cells (24 h, p < 0.05) compared to the untreated cells. However, L. fermentum did not inhibit CRL-1831 non-neoplastic colon cell growth but had a significant anti-proliferative effect against Caco-2 cancer cells (~ 60%, 72 h, p < 0.001) compared to control, which was related to the higher levels of SCFAs produced (~ 377 mg/L). Similar concentrations of SCFA formulations (that correspond to what was produced by L. fermentum) have shown the same inhibitory effect on Caco-2 cells. Conclusion: L. fermentum NCIMB 5221 was more potent in suppressing colon cancer cells and promoting normal epithelial colon cell growth by the production of SCFAs and could be considered as biotherapeutic agent for the support of colonic health and the prevention of colorectal cancer.

Effect of the bread-making process on zearalenone levels

The effects of the bread-making process including fermentation with Saccharomyces cerevisiae and lactic acid bacteria (Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus acidophilus and Lactobacillus fermentum) and baking at 200°C on zearalenone (ZEA) levels were investigated. Standard solutions of ZEA were added to flour and then loaves of bread were prepared. Sourdough and three types of yeast including active dry yeast, instant dry yeast and compressed yeast were used for the fermentation of dough. ZEA levels in flour, dough and bread were determined by HPLC with fluorescence detection after extraction and clean-up on an immunoaffinity column. The highest reduction in levels of ZEA was found in the first fermentation (first proof), while the lowest reduction was observed in the baking stage. In addition, the results showed that compressed yeast had the maximum reduction potential on ZEA levels even at the baking stage.

Flavour formation from hydrolysis of pork sarcoplasmic protein extract by a unique LAB culture isolated from Harbin dry sausage

The lactic acid bacteria Pediococcus pentosaceus, Lactobacillus brevis, Lactobacillus curvatus, and Lactobacillus fermentum isolated from Harbin dry sausage were assessed for their protein hydrolysis and flavour development in pork muscle sarcoplasmic protein extracts. Gel electrophoresis indicated that sarcoplasmic proteins were degraded by all of the strains, especially by P. pentosaceus and L. curvatus. Trichloroacetic acid-soluble peptides increased in all of the samples (P<0.05), especially samples inoculated with P. pentosaceus. Samples inoculated with P. pentosaceus and L. curvatus had higher free amino acid contents than did the other two strains (P<0.05), and glutamic acid and alanine appeared to be the predominant free amino acids. The volatile compound analysis indicated that the highest aldehydes, alcohols and acid contents were found in the sample with P. pentosaceus followed by L. curvatus. The results revealed that P. pentosaceus could be appropriate for use as a meat starter culture.

A methodological approach to screen diverse cheese-related bacteria for their ability to produce aroma compounds

Microorganisms play an important role in the development of cheese flavor. The aim of this study was to develop an approach to facilitate screening of various cheese-related bacteria for their ability to produce aroma compounds. We combined i) curd-based slurry medium incubated under conditions mimicking cheese manufacturing and ripening, ii) powerful method of extraction of volatiles, headspace trap, coupled to gas chromatography-mass spectrometry (HS-trap-GC-MS), and iii) metabolomics-based method of data processing using the XCMS package of R software and multivariate analysis. This approach was applied to eleven species: five lactic acid bacteria (Leuconostoc lactis, Lactobacillus sakei, Lactobacillus paracasei, Lactobacillus fermentum, and Lactobacillus helveticus), four actinobacteria (Brachybacterium articum, Brachybacterium tyrofermentans, Brevibacterium aurantiacum, and Microbacterium gubbeenense), Propionibacterium freudenreichii, and Hafnia alvei. All the strains grew, with maximal populations ranging from 7.4 to 9.2 log (CFU/mL). In total, 52 volatile aroma compounds were identified, of which 49 varied significantly in abundance between bacteria. Principal component analysis of volatile profiles differentiated species by their ability to produce ethyl esters (associated with Brachybacteria), sulfur compounds and branched-chain alcohols (H. alvei), branched-chain acids (H. alvei, P. freudenreichii and L. paracasei), diacetyl and related carbonyl compounds (M. gubbeenense and L. paracasei), among others.

Production of Traditional Sorghum Beer “&amp;lt;i&amp;gt;Ikigage&amp;lt;/i&amp;gt;” Using &amp;lt;i&amp;gt;Saccharomyces cerevisae&amp;lt;/i&amp;gt;,&amp;lt;i&amp;gt; Lactobacillus fermentum&amp;lt;/i&amp;gt; and&amp;lt;i&amp;gt; Issatckenkia orientalis&amp;lt;/i&amp;gt; as Starter Cultures

This study was carried out to evaluate the potential of the use of predominant yeast strains (Sacharomyces cerevisiae and Issatkenkia orientalis) and lactic acid bacteria (Lactobacillus fermentum) of Rwandese traditional sorghum beer “ikigage” as starter cultures to improve ikigage beer. The results show that L. fermentum has an influence on taste sour of ikigage beer and contributes also to generating ethyl acetate, ethyl lactate and higher alcohols such as 3-methylbutan-1-ol, 2-me- thylbutan-1-ol and 2-methylpropan-1-ol of this beer. I. orientalis contributed to the production of ethyl butyrate, ethyl caprylate, isobutyl butyrate and their corresponding acids, and to the generation of phenyl alcohols in ikigage beer. The association of S. cerevisiae with I. orientalis and L. fermentum produced ikigage beer with taste, aroma and mouth feel more similar to ikigage beers brewed locally by peasants. It is recommended to use S. cerevisiae in association with L. fermentum and I. orientalis as stater cultures to produce ikigage beer having the uniform organoleptic characteristics and a high ethanol content. This method also reduces the risk of contamination of the brew with food sanitary indicator and pathogenic microorganisms and will increase the chance of preservation of ikigage beer.

Yeasts are essential for cocoa bean fermentation

Cocoa beans (Theobroma cacao) are the major raw material for chocolate production and fermentation of the beans is essential for the development of chocolate flavor precursors. In this study, a novel approach was used to determine the role of yeasts in cocoa fermentation and their contribution to chocolate quality. Cocoa bean fermentations were conducted with the addition of 200ppm Natamycin to inhibit the growth of yeasts, and the resultant microbial ecology and metabolism, bean chemistry and chocolate quality were compared with those of normal (control) fermentations. The yeasts Hanseniaspora guilliermondii, Pichia kudriavzevii and Kluyveromyces marxianus, the lactic acid bacteria Lactobacillus plantarum and Lactobacillus fermentum and the acetic acid bacteria Acetobacter pasteurianus and Gluconobacter frateurii were the major species found in the control fermentation. In fermentations with the presence of Natamycin, the same bacterial species grew but yeast growth was inhibited. Physical and chemical analyses showed that beans fermented without yeasts had increased shell content, lower production of ethanol, higher alcohols and esters throughout fermentation and lesser presence of pyrazines in the roasted product. Quality tests revealed that beans fermented without yeasts were purplish-violet in color and not fully brown, and chocolate prepared from these beans tasted more acid and lacked characteristic chocolate flavor. Beans fermented with yeast growth were fully brown in color and gave chocolate with typical characters which were clearly preferred by sensory panels. Our findings demonstrate that yeast growth and activity were essential for cocoa bean fermentation and the development of chocolate characteristics.

Acid adaptation to improve viability and X‐prolyl dipeptidyl aminopeptidase activity of the probiotic bacterium Lactobacillus fermentum HA6 exposed to simulated gastrointestinal tract conditions

SummaryIn this work, the viability of the probiotic bacterium Lactobacillus fermentum HA6 isolated from naturally fermented vegetables in Vietnam was improved by growing the bacterium into a mild acid condition (pH 4.0). Viability and probiotic functionality [X‐prolyl dipeptidyl aminopeptidase (PepX) activity] of the acid‐adapted bacterium exposed to simulated gastrointestinal conditions were investigated. After 180 min in the simulated gastric juice (0.3 g/L pepsin, pH 2.0), the viability of acid‐adapted L. fermentum HA6 (11.5%) was higher than that of control L. fermentum HA6 (2.2%). Specific PepX activity of acid‐adapted cells (24.5 U/mg) was higher than that of control cells (17.8 U/mg). After 180‐min exposure to the simulated small intestinal medium (0.3 g/L bile salts, 0.1 g/L pancreatin, pH 8.0), the viability of acid‐adapted L. fermentum HA6 (13.5%) was twofold as high as that of control L fermentum HA6 (8.0%). Our results suggested that acid adaptation has a key role in acquiring cross‐protection mechanism, which in this study resulted in higher survival of L. fermentum HA6 after simulated gastrointestinal stresses. The strategy of acid adaptation could be valuable for the production of robust probiotics.