scispace - formally typeset
Search or ask a question

Showing papers on "Yeast published in 2021"


Journal ArticleDOI
TL;DR: In this paper, the impact of phenolics on the metabolism of microorganisms and fermentation process, although complex, is reviewed for the first time, highlighting the general effect of fermentation on the food's phenolic content, and its bioaccessibility, bioavailability and bioactivities including antioxidant capacity, anti-cancer, antidiabetic, antiinflammation, antiobesity properties.

58 citations


Journal ArticleDOI
TL;DR: In this paper, the potential of bioethanol production from macroalgae (Rhizoclonium sp.) biomass was evaluated by two-way separate hydrolysis and fermentation (SHF), and the fermentation process was carried at 30 to 35 °C in the incubator.
Abstract: Macroalgae are considered to be one of the rich lignocellulosic biomass materials. Aquatic biomass has gained more attention to biofuels generation in recent years due to its renewable, abundant, and environmentally friendly aspects. Macroalgae are photosynthetic organisms that are found in both marine and freshwater environments. These are considered as a third-generation feedstock for the production of biofuels since they have the ability to synthesize a high amount of lipids, proteins, and carbohydrates. This research study aimed to evaluate the potential of bioethanol production from macroalgae (Rhizoclonium sp.) biomass. The fermentation process was applied in the research by two-way separate hydrolysis and fermentation (SHF). Algae biomass undergoes a pretreatment process to release necessary sugars for yeast digestion. The fermentation process was carried at 30 to 35 °C in the incubator. Finally, the percentage of ethanol was estimated by the ebulliometer. Fermentation was enhanced by immobilization of yeast, which showed the highest concentration of ethanol (65.43 ± 18.13 g/l) after 96 h of fermentation and can be reused for several times for fermentation. Moreover, these study results confirmed that freshwater macroalgae biomass is a suitable and susceptible raw material for bioethanol production.

43 citations


Journal ArticleDOI
TL;DR: Pichia kluyveri is considered a low or non-fermentative yeast, so subsequent inoculation of a more fermentative yeast such as Saccharomyces cerevisiae is indispensable to achieve a proper fermented alcohol as mentioned in this paper.
Abstract: The surfaces of grapes are covered by different yeast species that are important in the first stages of the fermentation process. In recent years, non-Saccharomyces yeasts such as Torulaspora delbrueckii, Lachancea thermotolerans, Metschnikowia pulcherrima, and Pichia kluyveri have become popular with regard to winemaking and improved wine quality. For that reason, several manufacturers started to offer commercially available strains of these non-Saccharomyces species. P. kluyveri stands out, mainly due to its contribution to wine aroma, glycerol, ethanol yield, and killer factor. The metabolism of the yeast allows it to increase volatile molecules such as esters and varietal thiols (aroma-active compounds), which increase the quality of specific varietal wines or neutral ones. It is considered a low- or non-fermentative yeast, so subsequent inoculation of a more fermentative yeast such as Saccharomyces cerevisiae is indispensable to achieve a proper fermented alcohol. The impact of P. kluyveri is not limited to the grape wine industry; it has also been successfully employed in beer, cider, durian, and tequila fermentation, among others, acting as a promising tool in those fermentation processes. Although no Pichia species other than P. kluyveri is available in the regular market, several recent scientific studies show interesting improvements in some wine quality parameters such as aroma, polysaccharides, acid management, and color stability. This could motivate yeast manufacturers to develop products based on those species in the near future.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the microbial interactions in sugarcane ethanol fermentation were analyzed by combinatorically reconstituting every possible combination of species, comprising approximately 80% of the biodiversity in terms of relative abundance.
Abstract: Sugarcane ethanol fermentation represents a simple microbial community dominated by S. cerevisiae and co-occurring bacteria with a clearly defined functionality. In this study, we dissect the microbial interactions in sugarcane ethanol fermentation by combinatorically reconstituting every possible combination of species, comprising approximately 80% of the biodiversity in terms of relative abundance. Functional landscape analysis shows that higher-order interactions counterbalance the negative effect of pairwise interactions on ethanol yield. In addition, we find that Lactobacillus amylovorus improves the yeast growth rate and ethanol yield by cross-feeding acetaldehyde, as shown by flux balance analysis and laboratory experiments. Our results suggest that Lactobacillus amylovorus could be considered a beneficial bacterium with the potential to improve sugarcane ethanol fermentation yields by almost 3%. These data highlight the biotechnological importance of comprehensively studying microbial communities and could be extended to other microbial systems with relevance to human health and the environment.

37 citations


Journal ArticleDOI
TL;DR: This work studied the autochthonous Saccharomyces and non-Saccharomycing yeasts, isolated from various food sources, with the ability to modify and improve the fermentative and aromatic profiles during alcoholic fermentation, resulting in a promising yeast to produce fruity beers.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of individual inhibitors in inhibitor-rich lignocellulose hydrolysates has been investigated by spiking higher concentrations of each compound in a concentration range relevant for industrial enzymes.
Abstract: Presence of inhibitory chemicals in lignocellulose hydrolysates is a major hurdle for production of second-generation bioethanol. Especially cheaper pre-treatment methods that ensure an economical viable production process generate high levels of these inhibitory chemicals. The effect of several of these inhibitors has been extensively studied with non-xylose-fermenting laboratory strains, in synthetic media, and usually as single inhibitors, or with inhibitor concentrations much higher than those found in lignocellulose hydrolysates. However, the relevance of individual inhibitors in inhibitor-rich lignocellulose hydrolysates has remained unclear. The relative importance for inhibition of ethanol fermentation by two industrial second-generation yeast strains in five lignocellulose hydrolysates, from bagasse, corn cobs and spruce, has now been investigated by spiking higher concentrations of each compound in a concentration range relevant for industrial hydrolysates. The strongest inhibition was observed with industrially relevant concentrations of furfural causing partial inhibition of both D-glucose and D-xylose consumption. Addition of 3 or 6 g/L furfural strongly reduced the ethanol titer obtained with strain MD4 in all hydrolysates evaluated, in a range of 34 to 51% and of 77 to 86%, respectively. This was followed by 5-hydroxymethylfurfural, acetic acid and formic acid, for which in general, industrially relevant concentrations caused partial inhibition of D-xylose fermentation. On the other hand, spiking with levulinic acid, 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid or vanillin caused little inhibition compared to unspiked hydrolysate. The further evolved MD4 strain generally showed superior performance compared to the previously developed strain GSE16-T18. The results highlight the importance of individual inhibitor evaluation in a medium containing a genuine mix of inhibitors as well as the ethanol that is produced by the fermentation. They also highlight the potential of increasing yeast inhibitor tolerance for improving industrial process economics.

34 citations


Journal ArticleDOI
14 Jul 2021-Polymers
TL;DR: In this article, the authors developed edible and bioactive food packaging films comprising yeast incorporated into bacterial cellulose (BC) in conjunction with carboxymethyl cellulose and glycerol (Gly) to extend the shelf life of packaged food materials.
Abstract: The unique properties and advantages of edible films over conventional food packaging have led the way to their extensive exploration in recent years. Moreover, the incorporation of bioactive components during their production has further enhanced the intrinsic features of packaging materials. This study was aimed to develop edible and bioactive food packaging films comprising yeast incorporated into bacterial cellulose (BC) in conjunction with carboxymethyl cellulose (CMC) and glycerol (Gly) to extend the shelf life of packaged food materials. First, yeast biomass and BC hydrogels were produced by Meyerozyma guilliermondii (MT502203.1) and Gluconacetobacter xylinus (ATCC53582), respectively, and then the films were developed ex situ by mixing 30 wt.% CMC, 30 wt.% Gly, 2 wt.% yeast dry biomass, and 2 wt.% BC slurry. FE-SEM observation showed the successful incorporation of Gly and yeast into the fibrous cellulose matrix. FTIR spectroscopy confirmed the development of composite films through chemical interaction between BC, CMC, Gly, and yeast. The developed BC/CMC/Gly/yeast composite films showed high water solubility (42.86%). The yeast-incorporated films showed antimicrobial activities against three microbial strains, including Escherichia coli, Pseudomonas aeruginosa, and Saccharomyces aureus, by producing clear inhibition zones of 16 mm, 10 mm, and 15 mm, respectively, after 24 h. Moreover, the films were non-toxic against NIH-3T3 fibroblast cells. Finally, the coating of oranges and tomatoes with BC/CMC/Gly/yeast composites enhanced the shelf life at different storage temperatures. The BC/CMC/Gly/yeast composite film-coated oranges and tomatoes demonstrated acceptable sensory features such as odor and color, not only at 6 °C but also at room temperature and further elevated temperatures at 30 °C and 40 °C for up to two weeks. The findings of this study indicate that the developed BC/CMC/Gly/yeast composite films could be used as edible packaging material with high nutritional value and distinctive properties related to the film component, which would provide protection to foods and extend their shelf life, and thus could find applications in the food industry.

32 citations


Journal ArticleDOI
TL;DR: In this paper, the advances in yeast gene manipulation tools and techniques for heterologous pharmaceutical protein synthesis are reviewed, including secretory pathway engineering, glycosylation engineering strategies and fermentation scale-up strategies in customizing yeast cells for the synthesis of therapeutic proteins has been meticulously described.
Abstract: The manufacture of recombinant therapeutics is a fastest-developing section of therapeutic pharmaceuticals and presently plays a significant role in disease management. Yeasts are established eukaryotic host for heterologous protein production and offer distinctive benefits in synthesising pharmaceutical recombinants. Yeasts are proficient of vigorous growth on inexpensive media, easy for gene manipulations, and are capable of adding post translational changes of eukaryotes. Saccharomyces cerevisiae is model yeast that has been applied as a main host for the manufacture of pharmaceuticals and is the major tool box for genetic studies; nevertheless, numerous other yeasts comprising Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Yarrowia lipolytica have attained huge attention as non-conventional partners intended for the industrial manufacture of heterologous proteins. Here we review the advances in yeast gene manipulation tools and techniques for heterologous pharmaceutical protein synthesis. Application of secretory pathway engineering, glycosylation engineering strategies and fermentation scale-up strategies in customizing yeast cells for the synthesis of therapeutic proteins has been meticulously described.

32 citations


Journal ArticleDOI
TL;DR: Insight is provided into the microbial dynamics and higher alcohol formation, as well as an efficient strategy for process improvement in Baijiu fermentation.

31 citations


Journal ArticleDOI
TL;DR: Beyond the characterizing two previously unknown plant enzymes and conducting the first biosynthesis of icaritin from glucose, two strategies of overcoming the widespread issue of incompatible pH conditions encountered in basic and applied bioproduction research are described.
Abstract: Icaritin is a prenylflavonoid present in the Chinese herbal medicinal plant Epimedium spp. and is under investigation in a phase III clinical trial for advanced hepatocellular carcinoma. Here, we report the biosynthesis of icaritin from glucose by engineered microbial strains. We initially designed an artificial icaritin biosynthetic pathway by identifying a novel prenyltransferase from the Berberidaceae-family species Epimedium sagittatum (EsPT2) that catalyzes the C8 prenylation of kaempferol to yield 8-prenlykaempferol and a novel methyltransferase GmOMT2 from soybean to transfer a methyl to C4’-OH of 8-prenlykaempferol to produce icaritin. We next introduced 11 heterologous genes and modified 12 native yeast genes to construct a yeast strain capable of producing 8-prenylkaempferol with high efficiency. GmOMT2 was sensitive to low pH and lost its activity when expressed in the yeast cytoplasm. By relocating GmOMT2 into mitochondria (higher pH than cytoplasm) of the 8-prenylkaempferol–producing yeast strain or co-culturing the 8-prenylkaempferol–producing yeast with an Escherichia coli strain expressing GmOMT2, we obtained icaritin yields of 7.2 and 19.7 mg/L, respectively. Beyond the characterizing two previously unknown plant enzymes and conducting the first biosynthesis of icaritin from glucose, we describe two strategies of overcoming the widespread issue of incompatible pH conditions encountered in basic and applied bioproduction research. Our findings will facilitate industrial-scale production of icaritin and other prenylflavonoids.

30 citations


Journal ArticleDOI
TL;DR: Zhang et al. as mentioned in this paper characterized microbial community dynamics and associated biochemical changes in 12% salted Zhacai during a 90-day spontaneous fermentation process using high-throughput sequencing and chromatography-based approaches to identify associations between microorganisms and fermentation characteristics.


Journal ArticleDOI
TL;DR: In this article, the authors investigated the probiotic potential of yeast isolated from naturally fermented Brazilian table olives and found that the resulting Yeasts exhibited a hydrophobic cell surface (42.5-92.2%), autoaggregation capacity (41.0-91.0%), and adhesion to Caco-2 and HT-29 epithelial cell lines.
Abstract: Aims To investigate the probiotic potential of yeasts isolated from naturally fermented Brazilian table olives. Methods and results Eighteen yeast strains were tested in terms of: safety; survival of gastrointestinal and digestion conditions; antimicrobial activity; cellular hydrophobicity; autoaggregation ability and adhesion to epithelial cells; coaggregation and inhibition of pathogenic bacteria adhesion. Six yeasts showed favorable results for all probiotic attributes: Saccharomyces cerevisiae CCMA1746, Pichia guilliermondii CCMA1753, Candida orthopsilosis CCMA1748, Candida tropicalis CCMA1751, Meyerozyma caribbica CCMA1758, and Debaryomyces hansenii CCMA1761. These yeasts demonstrated resistance to 37 °C, pH 2.0, and bile salts, and survived in vitro digestion (≥ 106 CFU.mL-1 ). Further, the yeasts exhibited a hydrophobic cell surface (42.5-92.2%), autoaggregation capacity (41.0-91.0%), and adhesion to Caco-2 (62.0-82.8%) and HT-29 (57.6-87.3%) epithelial cell lines. Also, the strains showed antimicrobial activity against Salmonella enteritidis as well as the ability to coaggregate and reduce the adhesion of this pathogen to intestinal cells. Conclusions Autochthonous yeasts from naturally fermented Brazilian table olives have probiotic properties, with potential for development of new probiotic food products. Significance and impact of study These data are important and contribute to the knowledge of new potential probiotic yeasts capable of surviving gastrointestinal tract (GIT) conditions and inhibiting pathogenic bacteria.

Journal ArticleDOI
TL;DR: Zhang et al. as mentioned in this paper investigated the role of volatile compound-mediated microbial interaction in microbiome assembly and discovered a plausible scenario in which Pichia antagonized fungal blooms.
Abstract: Volatile organic compounds (VOCs) are chemicals responsible for antagonistic activity between microorganisms. The impact of VOCs on microbial community succession of fermentation is not well understood. In this study, Pichia spp. were evaluated for VOC production as a part of antifungal activity during baijiu fermentation. The results showed that the abundance of Pichia in the defect group (agglomerated fermented grains) was lower than that in control group, and a negative interaction between Pichia and Monascus was determined (P < 0.05). In addition, the disruption of fungi was significantly related to the differences of metabolic profiles in fermented grains. To determine production of VOCs from Pichia and its effect on Monascus purpureus, a double-dish system was assessed, and the incidence of M. purpureus reduction was 39.22% after 7 days. As to antifungal volatile compounds, 2-phenylethanol was identified to have an antifungal effect on M. purpureus through contact and noncontact. To further confirm the antifungal activity of 2-phenylethanol, scanning electron microscopy showed that 2-phenylethanol widely and significantly inhibited conidium germination and mycelial growth of filamentous fungi. Metatranscriptomic analysis revealed that the Ehrlich pathway is the metabolic path of 2-phenylethanol in Pichia and identified potential antifungal mechanisms, including protein synthesis and DNA damage. This study demonstrated the role of volatile compound-mediated microbial interaction in microbiome assembly and discovered a plausible scenario in which Pichia antagonized fungal blooms. The results may improve the niche establishment and growth of the functional yeast that enhances the flavor of baijiu.IMPORTANCE Fermentation of food occurs within communities of interacting species. The importance of microbial interactions in shaping microbial structure and metabolic performance to optimize the traditional fermentation process has long been emphasized, but the interaction mechanisms remain unclear. This study applied metabolome analysis and amplicon sequencing along with metatranscriptomic analysis to examine the volatile organic compound-mediated antifungal activity of Pichia and its effect on the metabolism of ethanol during baijiu fermentation, potentially enhancing the establishment of the fermentation niche and improving ethanol metabolism.

Journal ArticleDOI
TL;DR: In this paper, a morphologically engineered Yarrowia lipolytica strain was constructed via the integration of multiple copies of 13 genes related to the β-carotene biosynthesis pathway.
Abstract: The oleaginous yeast Yarrowia lipolytica represents an environmentally friendly platform cell factory for β-carotene production. However, Y. lipolytica is a dimorphic species that can undergo a yeast-to-mycelium transition when exposed to stress. The mycelial form is unfavorable for industrial fermentation. In this study, β-carotene-producing Y. lipolytica strains were constructed via the integration of multiple copies of 13 genes related to the β-carotene biosynthesis pathway. The β-carotene content increased by 11.7-fold compared with the start strain T1. As the β-carotene content increased, the oval-shaped yeast form was gradually replaced by hyphae, implying that the accumulation of β-carotene in Y. lipolytica induces a morphological transition. To relieve this metabolic stress, the strains were morphologically engineered by deleting CLA4 and MHY1 genes to convert the mycelium back to the yeast form, which further increased the β-carotene production by 139%. In fed-batch fermentation, the engineered strain produced 7.6 g/L and 159 mg/g DCW β-carotene, which is the highest titer and content reported to date. The morphological engineering strategy developed here may be useful for enhancing chemical synthesis in dimorphic yeasts.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate that acetate can be rapidly co-consumed with xylose by engineered Saccharomyces cerevisiae, which leads to a metabolic re-configuration that boosts the synthesis of acetyl-CoA derived bioproducts, including triacetic acid lactone and vitamin A, in engineered strains.
Abstract: Plant cell wall hydrolysates contain not only sugars but also substantial amounts of acetate, a fermentation inhibitor that hinders bioconversion of lignocellulose. Despite the toxic and non-consumable nature of acetate during glucose metabolism, we demonstrate that acetate can be rapidly co-consumed with xylose by engineered Saccharomyces cerevisiae. The co-consumption leads to a metabolic re-configuration that boosts the synthesis of acetyl-CoA derived bioproducts, including triacetic acid lactone (TAL) and vitamin A, in engineered strains. Notably, by co-feeding xylose and acetate, an enginered strain produces 23.91 g/L TAL with a productivity of 0.29 g/L/h in bioreactor fermentation. This strain also completely converts a hemicellulose hydrolysate of switchgrass into 3.55 g/L TAL. These findings establish a versatile strategy that not only transforms an inhibitor into a valuable substrate but also expands the capacity of acetyl-CoA supply in S. cerevisiae for efficient bioconversion of cellulosic biomass. Cellulosic hydrolysates contain substantial amounts of acetate, which is toxic to fermenting microorganisms. Here, the authors engineer Baker’s yeast to co-consume xylose and acetate for triacetic acid lactone production from a hemicellulose hydrolysate of switchgrass.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the microbiological and biochemical characteristics of six endogenous yeast species isolated from spontaneous wet coffee fermentation for their potential as starter cultures, and found that Hanseniaspora uvarum and Pichia kudriavzevii were the most stress-tolerant species and also exhibited high pectinase, amylase, cellulase and protease activities compared with P. fermentans.
Abstract: This study investigated the microbiological and biochemical characteristics of six endogenous yeast species isolated from spontaneous wet coffee fermentation for their potential as starter cultures. The yeasts were cultured under elevated temperature, osmotic pressure, ethanol and acid concentrations to assess their tolerance to these coffee fermentation-related stress conditions. Their ability to produce hydrolytic enzymes for pectin, protein, cellulose and starch were evaluated using plate assays. Hanseniaspora uvarum and Pichia kudriavzevii were the most stress-tolerant species and also exhibited high pectinase, amylase, cellulase and protease activities compared with P. fermentans, Candida railenensis, C. xylopsoci and Wickerhamomyces anomalus. When the yeasts were inoculated in a synthetic coffee pulp extract medium all the isolates grew and produced several important aromatic compounds, including isoamyl alcohol, 2-phenylethyl alcohol, ethanol, ethyl acetate, acetaldehyde, and 2-propanone. The concentrations of these volatiles produced by the yeast species differed significantly. H. uvarum and P. kudriavzevii produced significantly higher concentration of total alcohols (42.5, 57.6 mg/l), esters (31.0, 33.7 mg/l) and aldehydes (0.7, 1.9 mg/l). Overall, H. uvarum and P. kudriavzevii demonstrated the strongest potential as starter cultures for wet coffee fermentation.

Journal ArticleDOI
TL;DR: Saponification of yeast cells with alcoholic KOH and further extraction with hexane was the most appropriate method to extract and separate lipids and carotenoids from oleaginous yeast.

Journal ArticleDOI
TL;DR: This review summarizes previous studies on yeast-derived peptides, the production methods, the bioactivity, the mechanism of action, as well as the structure-function relationship, and stability of identified peptides.
Abstract: Background Yeast cells are a rich source of protein and have long been investigated for the production of yeast extract as a source of bioactive peptides with different documented bioactivity, e.g. antioxidant, ACE-inhibitory, antidiabetic, as well as prevention of chronic diseases and providing immune responces. Furthermore, yeast cells are known to contribute to generation of bioactive peptides due to their proteolytic activity during fermentation processes, and also release of antimicrobial peptides during growth. Scope and approach Although reports on preparation and characteristic of yeast extract increased tremendously, research on the functional properties of yeast extract attributed to the content of bioactive peptides and production methods lack a systematic review. Also, the contribution of yeast cells to the production of bioactive peptides during the growth and fermentation process has not been summarized previously. This review summarizes previous studies on yeast-derived peptides, the production methods, the bioactivity, the mechanism of action, as well as the structure-function relationship, and stability of identified peptides. This article would be helpful to promote the application of yeast-derived peptides in research and commercialization. Key finding Yeast cells and yeast extract have great potentials for producing bioactive peptides with multiple functionalities. Current scientific evidence regarding the potential health benefit of yeast highlights the need for additional investigation on the bioactivity of peptides as influenced by production and purification methods. Also, predicting and designing new peptide sequences with specific functionality with the aid of bioinformatics tools, animal and human studies will effectively transfer these findings into practical and market applications.

Journal ArticleDOI
TL;DR: In this paper, the first report on the microbiota of kefir produced in Greece by a holistic approach combining classical microbiological, molecular, and amplicon-based metagenomics analyses was presented.
Abstract: Kefir is a high nutritional fermented dairy beverage associated with a wide range of health benefits. It constitutes a unique symbiotic association, comprising mainly lactic acid bacteria, yeasts, and occasionally acetic acid bacteria, which is strongly influenced by the geographical origin of the grains, the type of milk used, and the manufacture technology applied. Until recently, kefir microbiota has been almost exclusively studied by culture-dependent techniques. However, high-throughput sequencing, alongside omics approaches, has revolutionized the study of food microbial communities. In the present study, the bacterial, and yeast/fungal microbiota of four home-made samples (both grains and drinks), deriving from well spread geographical regions of Greece, and four industrial beverages, was elucidated by culture-dependent and -independent analyses. In all samples, classical microbiological analysis revealed varying populations of LAB and yeasts, ranging from 5.32 to 9.60 log CFU mL-1 or g-1, and 2.49 to 7.80 log CFU mL-1 or g-1, respectively, while in two industrial samples no yeasts were detected. Listeria monocytogenes, Salmonella spp. and Staphylococcus spp. were absent from all the samples analyzed, whereas Enterobacteriaceae were detected in one of them. From a total of 123 isolates, including 91 bacteria and 32 yeasts, Lentilactobacillus kefiri, Leuconostoc mesenteroides, and Lactococcus lactis as well as Kluvyeromyces marxianus and Saccharomyces cerevisiae were the mostly identified bacterial and yeast species, respectively, in the home-made samples. On the contrary, Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Lacticaseibacillus rhamnosus along with Debaryomyces hansenii and K. marxianus were the main bacterial and yeast species, respectively, isolated from the industrial beverages. In agreement with the identification results obtained from the culture-dependent approaches, amplicon-based metagenomics analysis revealed that the most abundant bacterial genera in almost all home-made samples (both grains and drinks) were Lactobacillus and Lactococcus, while Saccharomyces, Kazachstania, and Kluvyeromyces were the predominant yeasts/fungi. On the other hand, Streptococcus, Lactobacillus, and Lactococcus as well as Kluvyeromyces and Debaryomyces dominated the bacterial and yeast/fungal microbiota, respectively, in the industrial beverages. This is the first report on the microbiota of kefir produced in Greece by a holistic approach combining classical microbiological, molecular, and amplicon-based metagenomics analyses.

Journal ArticleDOI
TL;DR: In this article, the authors describe the process of obtaining insoluble β-glucans (particulate) from spent brewer's yeast and provide an insight into how a byproduct from brewing can be converted to potential food applications.
Abstract: In the brewing process, the consumption of resources and the amount of waste generated are high and due to a lot of organic compounds in waste-water, the capacity of natural regeneration of the environment is exceeded. Residual yeast, the second by-product of brewing is considered to have an important chemical composition. An approach with nutritional potential refers to the extraction of bioactive compounds from the yeast cell wall, such as β-glucans. Concerning the potential food applications with better textural characteristics, spent brewer’s yeast glucan has high emulsion stability and water-holding capacity fitting best as a fat replacer in different food matrices. Few studies demonstrate the importance and nutritional role of β-glucans from brewer’s yeast, and even less for spent brewer’s yeast, due to additional steps in the extraction process. This review focuses on describing the process of obtaining insoluble β-glucans (particulate) from spent brewer’s yeast and provides an insight into how a by-product from brewing can be converted to potential food applications.

Journal ArticleDOI
TL;DR: Different down-stream processing of S. cerevisiae led to increased protein and β-glucan solubility that further increased protein digestibility in Atlantic salmon, and different processing of the yeast triggered different immune stimulatory effects in Atlantic Salmon.

Journal ArticleDOI
TL;DR: Caffeic acid production in S. cerevisiae strain was successfully improved by adopting a glucose-regulated GAL system and comprehensive metabolic engineering strategies, showing the prospect for microbial biosynthesis of caffeic acid and laid the foundation for constructing biosynthetic pathways of its derived metabolites.
Abstract: As a natural phenolic acid product of plant source, caffeic acid displays diverse biological activities and acts as an important precursor for the synthesis of other valuable compounds. Limitations in chemical synthesis or plant extraction of caffeic acid trigger interest in its microbial biosynthesis. Recently, Saccharomyces cerevisiae has been reported for the biosynthesis of caffeic acid via episomal plasmid-mediated expression of pathway genes. However, the production was far from satisfactory and even relied on the addition of precursor. In this study, we first established a controllable and stable caffeic acid pathway by employing a modified GAL regulatory system to control the genome-integrated pathway genes in S. cerevisiae and realized biosynthesis of 222.7 mg/L caffeic acid. Combinatorial engineering strategies including eliminating the tyrosine-induced feedback inhibition, deleting genes involved in competing pathways, and overexpressing rate-limiting enzymes led to about 2.6-fold improvement in the caffeic acid production, reaching up to 569.0 mg/L in shake-flask cultures. To our knowledge, this is the highest ever reported titer of caffeic acid synthesized by engineered yeast. This work showed the prospect for microbial biosynthesis of caffeic acid and laid the foundation for constructing biosynthetic pathways of its derived metabolites. KEY POINTS: Genomic integration of ORgTAL, OHpaB, and HpaC for caffeic acid production in yeast. Feedback inhibition elimination and Aro10 deletion improved caffeic acid production. The highest ever reported titer (569.0 mg/L) of caffeic acid synthesized by yeast.

Journal ArticleDOI
TL;DR: The results showed higher weight gain and specific growth rate in shrimp fed diet YE2 compared with those fed the Control, and the effects of yeast and yeast extract on growth performance, anti-oxidant ability and intestinal microbiota of Litopenaeus vannamei.

Journal ArticleDOI
TL;DR: In this article, the main aspects of fuel ethanol production, emphasizing bioprocesses operating in North America and Brazil, are described, and the main properties of commercial yeast products (i.e., yeast strains) that are available worldwide to bioethanol producers.
Abstract: Fuel ethanol is produced by the yeast Saccharomyces cerevisiae mainly from corn starch in the United States and from sugarcane sucrose in Brazil, which together manufacture ∼85% of a global yearly production of 109.8 million m3 (in 2019). While in North America genetically engineered (GE) strains account for ∼80% of the ethanol produced, including strains that express amylases and are engineered to produce higher ethanol yields; in South America, mostly (>90%) non-GE strains are used in ethanol production, primarily as starters in non-aseptic fermentation systems with cell recycling. In spite of intensive research exploring lignocellulosic ethanol (or second generation ethanol), this option still accounts for <1% of global ethanol production. In this mini-review, we describe the main aspects of fuel ethanol production, emphasizing bioprocesses operating in North America and Brazil. We list and describe the main properties of several commercial yeast products (i.e., yeast strains) that are available worldwide to bioethanol producers, including GE strains with their respective genetic modifications. We also discuss recent studies that have started to shed light on the genes and traits that are important for the persistence and dominance of yeast strains in the non-aseptic process in Brazil. While Brazilian bioethanol yeast strains originated from a historical process of domestication for sugarcane fermentation, leading to a unique group with significant economic applications, in U.S.A., guided selection, breeding and genetic engineering approaches have driven the generation of new yeast products for the market.

Journal ArticleDOI
TL;DR: The prevalence of yeasts in food products, the impact of pathogenic yeasts on the human organism, and the possibility to suppress their growth by use of lactic acid bacteria and preservatives of plant origin are described.
Abstract: Background Yeasts are widely spread in nature. Yeasts have a positive role in the fermentation of some products such as wine or beer, although they are also responsible for food spoilage alongside fungi. In addition, some species of yeasts, such as Candida spp., can enter the human body through food and beverages and may cause various types of infections. Therefore, it is necessary to find natural means for inhibition yeast growth in foods where they are undesirable microorganisms. Scope and approach This work describes the prevalence of yeasts in food products, the impact of pathogenic yeasts on the human organism, and the possibility to suppress their growth by use of lactic acid bacteria and preservatives of plant origin. It may be applicable in food industries where yeasts are undesirable microorganisms which requires inhibition of their growth. Key findings Yeasts have a positive role in food fermentation, but can also cause infections in people, therefore their presence in food should be controlled. Lactic acid bacteria (LAB) are good inhibitors of fungal activity due to the presence of inhibitory compounds, such as lactic, acetic, and ascorbic acids, hydrogen peroxide, bacteriocins, and others. Out of LAB, Lactobacillus plantarum shows the strongest inhibitory effects. Furthermore, plant extracts, such as black walnut, clove, garlic, oregano leaf extracts, as well as anolyte – a natural disinfectant - also display an antifungal effect and could be used for yeast and fungal control.

Journal ArticleDOI
28 Jan 2021
TL;DR: In this paper, the impact of yeast extract and jasmonic acid on the induction of defense responses and consequently the production of phenolic acids in vitro hairy root cultures of O aristatus have been investigated.
Abstract: Phenolic acids represent a big group of plant secondary metabolites that can be used as food additives, nutraceuticals, and pharmaceuticals Obtaining phenolic acids from the plant in vitro cultures provide an attractive alternative to produce high-value plant-derived products The impact of yeast extract and jasmonic acid on the induction of defense responses and consequently the production of phenolic acids in vitro hairy root cultures of O aristatus have been investigated Treatment of O aristatus cultures with jasmonic acid caused accumulation of 1298 mgg-1 DW of phenolic acids, elicitation with yeast extract resulted in the highest amount of phenolic acids, particularly in 1799 mgg-1 DW as compared to 403 mgg-1 DW for the non-treated cultures Individual phenolic acids showed a different response to elicitation Particularly rosmarinic acid content on the control plot reached 289 mgg-1 DW, while after the treatment with jasmonic acid is increased to 1084 mgg-1 DW and after yeast application, it was 1431 mgg-1 DW Also, caffeic acid content increased until 075 and 201 mgg-1 DW after application of jasmonic acid and yeast extract, while at the control plot its concentration was 058 mgg-1 DW Application of yeast extract influenced synthesis of phenolic acids in vitro cultures of O aristatus stronger as jasmonic acid treatment

Journal ArticleDOI
27 May 2021-Yeast
TL;DR: In this paper, a review on acetic acid stress and its response in the context of cellular transport, pH homeostasis, metabolism and stress-signalling pathways is presented.
Abstract: Acetic acid stress represents a frequent challenge to counteract for yeast cells under several environmental conditions and industrial bioprocesses. The molecular mechanisms underlying its response have been mostly elucidated in the budding yeast Saccharomyces cerevisiae, where acetic acid can be either a physiological substrate or a stressor. This review will focus on acetic acid stress and its response in the context of cellular transport, pH homeostasis, metabolism and stress-signalling pathways. This information has been integrated with the results obtained by multi-omics, synthetic biology and metabolic engineering approaches aimed to identify major cellular players involved in acetic acid tolerance. In the production of biofuels and renewable chemicals from lignocellulosic biomass, the improvement of acetic acid tolerance is a key factor. In this view, how this knowledge could be used to contribute to the development and competitiveness of yeast cell factories for sustainable applications will be also discussed.

Journal ArticleDOI
TL;DR: This research demonstrates the applicability of Baker yeast cells in the design of microbial biofuel cells by applying PQ as a redox mediator for yeast-based MFC improves electron transfer through the yeast cell membrane and cell wall towards electrode without any noticeable decrease of yeast cell viability.