Forastero hybrid cocoa bean fermentations have been carried out in a box (B) and in a heap (H), with or without the inoculation of
and
as starter cultures. The bacteria, yeasts, and microbial ...metabolites (volatile and nonvolatile organic compounds) were monitored during fermentation to assess the connection between microbiota and the release of metabolites during this process. The presence of starter cultures was detected, by means of culture-dependent analysis, during the first 2 days of both fermentations. However, no statistical difference was observed in any of the physicochemical or microbiological analyses. Plate counts revealed the dominance of yeasts at the beginning of both fermentations, and these were followed by acetic acid bacteria (AAB) and lactic acid bacteria (LAB).
,
,
,
, and
were the most abundant operational taxonomic units (OTUs) during both fermentation processes (B and H), although different relative abundances were observed. Only the diversity of the fungal species indicated a higher level of complexity in the B fermentations than in the H fermentations (
< 0.05), as well as a statistically significant difference between the initially inoculated starter cultures (
< 0.01). However, the microbial metabolite analysis indicated different distributions of the volatile and nonvolatile compounds between the two procedures, that is, B and H (
< 0.05), rather than between the inoculated and noninoculated fermentations. The box fermentations showed faster carbohydrate metabolism and greater production of organic acid compounds, which boosted the formation of alcohols and esters, than did the heap fermentations. Overall, the microbial dynamics and associations between the bacteria, yeasts, and metabolites were found to depend on the type of fermentation.
In spite of the limited effectiveness of the considered inoculated starter strains, this study provides new information on the microbial development of box and heap cocoa fermentations, under inoculated and noninoculated conditions, as we coupled yeast/bacterial amplicon-based sequencing data with microbial metabolite detection. The information so far available suggests that microbial communities have played an important role in the evolution of aroma compounds. Understanding the pathways that microorganisms follow during the formation of aromas could be used to improve the fermentation processes and to enhance chocolate quality.
Understanding Kombucha Tea Fermentation: A Review Villarreal‐Soto, Silvia Alejandra; Beaufort, Sandra; Bouajila, Jalloul ...
Journal of food science,
March 2018, Letnik:
83, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Kombucha is a beverage of probable Manchurian origins obtained from fermented tea by a microbial consortium composed of several bacteria and yeasts. This mixed consortium forms a powerful symbiosis ...capable of inhibiting the growth of potentially contaminating bacteria. The fermentation process also leads to the formation of a polymeric cellulose pellicle due to the activity of certain strains of Acetobacter sp. The tea fermentation process by the microbial consortium was able to show an increase in certain biological activities which have been already studied; however, little information is available on the characterization of its active components and their evolution during fermentation. Studies have also reported that the use of infusions from other plants may be a promising alternative.
Practical Application
Kombucha is a traditional fermented tea whose consumption has increased in the recent years due to its multiple functional properties such as anti‐inflammatory potential and antioxidant activity. The microbiological composition of this beverage is quite complex and still more research is needed in order to fully understand its behavior. This study comprises the chemical and microbiological composition of the tea and the main factors that may affect its production.
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•Spent mushroom substrate (SMS) of Ganoderma lucidum was used.•SMS rich in beta glucan suitable for bioethanol production.•Optimized sulphuric acid concentration and SMS percentage ...for acid hydrolysis.•Fermented using S. cerevisiae for ethanol production.•Final ethanol yield obtained from SMS was 0.2 % v/v.
In this study, spent mushroom substrate (SMS) obtained from Ganoderma lucidum used as a potential biomass for bioethanol production was investigated. Sulphuric acid pretreatment of SMS was evaluated to optimize the sugar extraction through hydrolysis. The proximate composition of SMS was analysed. Total sugar and reducing sugar yield from SMS were calculated as 33.58 ± 0.17 mg/g and 8.28 ± 0.35 mg/g DW, respectively. Total organic carbon was recorded as 17.74 % DW. SMS pretreated with 1 % sulphuric acid yielded maximum total sugar of 807.53 ± 0.04 mg/g DW. Substrate and acid ratio was optimized for pretreatment and found that a ratio of 4:50 yielded maximum total and reducing sugar of 102.80 ± 0.73 mg/g and 12.68 ± 0.86 mg/g DW, respectively. Sugars obtained from SMS were fermented using baker’s yeast and incubated at 30 °C for 5 days. The final yield of 1.57 g L-1 of ethanol was produced on day 4 when compared with the theoretical ethanol yield of 0.91 g L-1 obtained. The present study concludes that SMS from Ganoderma lucidum considered being an alternate choice for bioethanol production to meet the biofuel demand in the future and utilization of mushroom wastes to generate energy with the concept of zero-waste discharge was emphasized.
The incidence of opportunistic yeast infections in humans has been increasing over recent years. These infections are difficult to treat and diagnose, in part due to the large number and broad ...diversity of species that can underlie the infection. In addition, resistance to one or several antifungal drugs in infecting strains is increasingly being reported, severely limiting therapeutic options and showcasing the need for rapid detection of the infecting agent and its drug susceptibility profile. Current methods for species and resistance identification lack satisfactory sensitivity and specificity, and often require prior culturing of the infecting agent, which delays diagnosis. Recently developed high-throughput technologies such as next generation sequencing or proteomics are opening completely new avenues for more sensitive, accurate and fast diagnosis of yeast pathogens. These approaches are the focus of intensive research, but translation into the clinics requires overcoming important challenges. In this review, we provide an overview of existing and recently emerged approaches that can be used in the identification of yeast pathogens and their drug resistance profiles. Throughout the text we highlight the advantages and disadvantages of each methodology and discuss the most promising developments in their path from bench to bedside.
Over the last years oleaginous yeasts have been studied for several energetic, oleochemical, medical and pharmaceutical purposes. However, only a small number of yeasts are known and have been deeply ...exploited. The search for new isolates with high oleaginous capacity becomes imperative, as well as the use of alternative and ecological carbon sources for yeast growth.
In the present study a high-throughput screening comprising 366 distinct yeast isolates was performed by applying an optimised protocol based on two approaches: (I) yeast cultivation on solid medium using acetic acid as carbon source, (II) neutral lipid estimation by fluorimetry using the lipophilic dye Nile red.
Results showed that, with the proposed methodology, the oleaginous potential of yeasts with broad taxonomic diversity and variety of growth characteristics was discriminated. Furthermore, this work clearly demonstrated the association of the oleaginous yeast character to the strain level, contrarily to the species-level linkage, as usually stated.
Abstract
Fungi represent a group of soil microorganisms fulfilling important ecological functions. Although several studies have shown that yeasts represent a significant proportion of fungal ...communities, our current knowledge is based mainly on cultivation experiments. In this study, we used amplicon sequencing of environmental DNA to describe the composition of yeast communities in European temperate forest and to identify the potential biotic and abiotic drivers of community assembly. Based on the analysis of ITS2 PCR amplicons, yeasts represented a substantial proportion of fungal communities ranging from 0.4 to 14.3% of fungal sequences in soil and 0.2 to 9.9% in litter. The species richness at individual sites was 28 ± 9 in soil and 31 ± 11 in litter. The basidiomycetous yeasts dominated over ascomycetous ones. In litter, yeast communities differed significantly among beech-, oak- and spruce-dominated stands. Drivers of community assembly are probably more complex in soils and comprise the effects of environmental conditions and vegetation.
We used amplicon sequencing of environmental DNA to describe the composition of yeast communities in European temperate forest soil and to identify the potential biotic and abiotic drivers of community assembly.
The molecular basis of how temperature affects cell metabolism has been a long-standing question in biology, where the main obstacles are the lack of high-quality data and methods to associate ...temperature effects on the function of individual proteins as well as to combine them at a systems level. Here we develop and apply a Bayesian modeling approach to resolve the temperature effects in genome scale metabolic models (GEM). The approach minimizes uncertainties in enzymatic thermal parameters and greatly improves the predictive strength of the GEMs. The resulting temperature constrained yeast GEM uncovers enzymes that limit growth at superoptimal temperatures, and squalene epoxidase (ERG1) is predicted to be the most rate limiting. By replacing this single key enzyme with an ortholog from a thermotolerant yeast strain, we obtain a thermotolerant strain that outgrows the wild type, demonstrating the critical role of sterol metabolism in yeast thermosensitivity. Therefore, apart from identifying thermal determinants of cell metabolism and enabling the design of thermotolerant strains, our Bayesian GEM approach facilitates modelling of complex biological systems in the absence of high-quality data and therefore shows promise for becoming a standard tool for genome scale modeling.
The last years there has been a significant rise in the number of publications in the international literature that deal with the production of lipids by microbial sources (the ‘single cell oils; ...SCOs’ that are produced by the so‐called ‘oleaginous’ micro‐organisms). In the first part of the present review article, a general overview of the oleaginous micro‐organisms (mostly yeasts, algae and fungi) and their potential upon the production of SCOs is presented. Thereafter, physiological and kinetic events related with the production of, mostly, yeast and fungal lipids when sugars and related substrates like polysaccharides, glycerol, etc. (the de novo lipid accumulation process) or hydrophobic substrates like oils and fats (the ex novo lipid accumulation process) were employed as microbial carbon sources, are presented and critically discussed. Considerations related with the degradation of storage lipid that had been previously accumulated inside the cells, are also presented. The interplay of the synthesis of yeast and fungal lipids with other intracellular (i.e. endopolysaccharides) or extracellular (i.e. citric acid) secondary metabolites synthesized is also presented. Finally, aspects related with the lipid extraction and lipidome analysis of the oleaginous micro‐organisms are presented and critically discussed.
Aims
The aim of this work was to identify 20 yeasts isolated from autochthonal cheese starters and evaluate their technological and functional properties.
Methods and Results
The capacities of the ...yeasts to grow at different temperatures, pH, NaCl and lactic acid concentrations as well as the proteolytic and lipolytic activities were studied. Moreover, survival to simulated gastrointestinal digestion, hydrophobicity, antimicrobial activity against pathogens and auto‐ and co‐aggregation abilities were evaluated. The sequentiation of a fragment from the 26S rDNA gene indicated that Kluyveromyces marxianus was the predominant species, followed by Saccharomyces cerevisiae, Clavispora lusitaniae, Kluyveromyces lactis and Galactomyces geotrichum. RAPD with primer M13 allowed a good differentiation among strains from the same species. All strains normally grew at pH 4·7–5·5 and temperatures between 15 and 35°C. Most of them tolerated 10% NaCl and 3% lactic acid. Some strains showed proteolytic (eight isolates) and/or lipolytic (four isolates) capacities. All strains evidenced high gastrointestinal resistance, moderate hydrophobicity, intermediate auto‐aggregation and variable co‐aggregation abilities. No strains inhibited the growth of the pathogens assayed.
Conclusions
Some strains from dairy sources showed interesting functional and technological properties.
Significance and Impact of the Study
This study has been the first contribution to the identification and characterization of yeasts isolated from autochthonal cheese starters in Argentina. Many strains could be proposed as potential candidates to be used as probiotics and/or as co‐starters in cheese productions.
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