Trophic relationships between Saccharomyces cerevisiae and Lactobacillus plantarum and their metabolism of glucose and citrate

Skincare potential of a sustainable postbiotic extract produced through sugarcane straw fermentation by Saccharomyces cerevisiae

Postbiotics are defined as a "preparation of inanimate microorganisms and/or their components that confers a health benefit on the host." They can be produced by fermentation, using culture media with glucose (carbon source), and lactic acid bacteria of the genus Lactobacillus, and/or yeast, mainly Saccharomyces cerevisiae as fermentative microorganisms. Postbiotics comprise different metabolites, and have important biological properties (antioxidant, anti-inflammatory, etc.), thus their cosmetic application should be considered. During this work, the postbiotics production was carried out by fermentation with sugarcane straw, as a source of carbon and phenolic compounds, and as a sustainable process to obtain bioactive extracts. For the production of postbiotics, a saccharification process was carried out with cellulase at 55°C for 24 h. Fermentation was performed sequentially after saccharification at 30°C, for 72 h, using S. cerevisiae. The cells-free extract was characterized regarding its composition, antioxidant activity, and skincare potential. Its use was safe at concentrations below ~20 mg mL-1 (extract's dry weight in deionized water) for keratinocytes and ~ 7.5 mg mL-1 for fibroblasts. It showed antioxidant activity, with ABTS IC50 of 1.88 mg mL-1 , and inhibited elastase and tyrosinase activities by 83.4% and 42.4%, respectively, at the maximum concentration tested (20 mg mL-1 ). In addition, it promoted the production of cytokeratin 14, and demonstrated anti-inflammatory activity at a concentration of 10 mg mL-1 . In the skin microbiota of human volunteers, the extract inhibited Cutibacterium acnes and the Malassezia genus. Shortly, postbiotics were successfully produced using sugarcane straw, and showed bioactive properties that potentiate their use in cosmetic/skincare products.

Impact of Leavening Agent and Wheat Variety on Bread Organoleptic and Nutritional Quality

Leavened bread can be made with different wheat varieties and leavening agents. Several studies have now demonstrated that each of these factors can play a role in bread quality. However, their relative impact in artisanal bread making remains to be elucidated. Here, we assessed the impact of two wheat varieties as well as the impact of sourdoughs and yeasts on multiple components of bread organoleptic and nutritional quality. Using a participatory research approach including scientists and bakers, we compared breads leavened with three different sourdoughs and three different commercial yeasts as well as a mix of sourdough and yeast. Breads were made from two wheat varieties commonly used in organic farming: the variety “Renan” and the landrace “Barbu”. Except for bread minerals contents that mostly depended on wheat variety, bread quality was mostly driven by the fermenting agent. Sourdough breads had lower sugar and organic acids contents. These differences were mostly attributable to lower amounts of maltose and malate. They also had a higher proportion of soluble proteins than yeast breads, with specific aroma profiles. Finally, their aroma profiles were specific and more diverse compared to yeast breads. Interestingly, we also found significant nutritional and organoleptic quality differences between sourdough breads. These results highlight the value of sourdough bread and the role of sourdough microbial diversity in bread nutritional and organoleptic quality.

Comparison of Fermentation Behaviors and Characteristics of Tomato Sour Soup between Natural Fermentation and Dominant Bacteria-Enhanced Fermentation

In this study, the correlations between microbial communities with physicochemical properties and volatile flavor compounds (VFCs) during the fermentation of traditional tomato sour soup (CTN) are explored. The results of high-throughput sequencing (HTS) of CTN showed that Lacticaseibacillus (28.67%), Enterobacter (12.37%), and Providencia (12.19%) were the dominant bacteria in the first round of fermentation, while Lacticaseibacillus (50.11%), Enterobacter (13.86%), and Providencia (8.61%) were the dominant bacteria in the second round of fermentation. Additionally, the dominant fungi genera of the first fermentation were Pichia (65.89%) and Geotrichum (30.56%), and the dominant fungi genera of the second fermentation were Pichia (73.68%), Geotrichum (13.99%), and Brettanomyces (5.15%). These results indicate that Lacticaseibacillus is one of the main dominant bacteria in CTN. Then, the dominant strain Lacticaseibacillus casei H1 isolated from CTN was used as a culture to ferment tomato sour soup to monitor dynamic changes in the physicochemical properties and VFCs during enhanced fermentation of tomato sour soup (TN). The physicochemical analysis showed that, compared with CTN, the TN group not only produced acid faster but also had an earlier peak of nitrite and a lower height. The results of the GC–IMS analysis showed that the ester and alcohol contents in the TN group were 1.26 times and 1.8 times that of the CTN group, respectively. Using an O2PLS-DA analysis, 11 bacterial genera and 18 fungal genera were identified as the functional core flora of the CTN group flavor production, further verifying the importance of dominant bacteria for the production of VFCs. This study proved that enhanced fermentation not only shortens the fermentation cycle of tomato sour soup, but also significantly improves its flavor quality, which has great value in the industrial production of tomato sour soup and in the development of a vegetable fermentation starter.

Deep insights into fungal diversity in traditional Chinese sour soup by Illumina MiSeq sequencing

Sour soup is a traditional condiment in Guizhou Province, China. The purpose of this study was to investigate the differences in the fungi present in 5 types of sour soup (tomato sour soup, chili sour soup, cherry tomato sour soup, spoiled tomato sour soup, and red sour soup made from blended tomato and chili sour soup subjected to secondary fermentation) and to determine the reasons for the deterioration of tomato sour soup by comparing the fungal communities in normal and deterioratedtomato sour soup. A total of 5 phyla were detected in all 5 samples, including Ascomycota (69.38%), Basidiomycota (7.63%), Zygomycota (1.59%), Chytridiomycota (0.01%) and unclassified phyla (21.39%). Ascomycota was the main phylum in each sample except the red sour soup made from blended tomato and chili sour soup subjected to secondary fermentation. That sour soup contained many unrecognized phyla. At the genus level, there were major differences among the different samples. Dekkera spp. and Pichia spp. were the main dominant fungus in tomato sour soup, Saccharomyces spp. and Pichia spp. were the dominant fungus in chili sour soup, and Pichia spp. were the dominant fungus in cherry tomato sour soup. When sour soup went bad, the fungus of sour soup changed greatly, and the unknown fungal genera, Cladospora spp., Saccharomyces spp. and Emericella spp. became the dominant fungal genera. In addition, after the secondary fermentation of tomato and chili sour soup mixed with garlic and ginger, the fungal genera of the base fermentation were replaced by unknown fungal genera. Moreover, there were various spoilage fungi in sour soup, which indicated that there were safety risks in naturally fermented sour soup and should be further controlled. This study revealed the fungal flora in sour soup made from different vegetables and compared the fungal diversity of spoiled and normal tomato sour soup and thereby provided a basis for understanding the fungal diversity of sour soup in China and guiding the production of sour soup.

Non-sterile fermentation of food waste with indigenous consortium and yeast - Effects on microbial community and product spectrum

This work presents examples of non-sterile mixed culture fermentation of food waste with a cultivated indigenous consortium (IC) gained from food waste, which produces lactic and acetic acids, combined with Saccharomyces cerevisiae, which produces ethanol. All results are flanked by microbial analysis to monitor changes in microbial community. At pH 6 and inoculated with yeast or IC, or both mixed sugars conversion was equal to 71%, 51%, or 67%, respectively. Under pH unregulated conditions metabolic yields were 71%, 67%, or up to 81%. While final titer of acetic acid was not affected by pH (100-200 mM), ethanol and lactic acid titers were. Using mixed culture and pH 6, sugars were almost equally used for formation of ethanol and lactic acid (400-500 mM). However, under pH unregulated conditions 80% of the substrate was converted into ethanol (900-1000 mM).

Effects of a high-dose Saccharomyces cerevisiae inoculum alone or in combination with Lactobacillus plantarum on the nutritional composition and fermentation traits of maize silage

Context The inoculation of silage with Saccharomyces cerevisiae to deliver viable yeast cells is a novel concept. Aims The effects of a high-dose S. cerevisiae inoculum alone or combined with Lactobacillus plantarum on the nutritional composition, fermentation traits and aerobic stability of maize silage were studied after 30, 60 and 90 days of storage. Methods Whole-crop maize (309.3 g dry matter (DM)/kg as fed) was subjected to one of three treatments: deionised water (untreated control); S. cerevisiae at an estimated concentration of 108 CFU/g fresh forage (S); or S. cerevisiae at an estimated concentration of 108 CFU/g and L. plantarum at an estimated concentration of 105 CFU/g of fresh forage (SL). Key results Compared with the control, the S and SL groups showed increases (P < 0.001) in average pH (3.98 in S and 4.01 in SL vs 3.65 in the control), crude protein (85 g/kg DM in S and 80 g/kg DM in SL vs 63 g/kg DM in the control) and ammonia nitrogen/total nitrogen (122.2 g/kg in S and 163.9 g/kg in SL vs 52.9 g/kg in the control) but a lower (P < 0.001) average concentration of water-soluble carbohydrate (0.9 g/kg DM in S and 0.7 g/kg DM in SL vs 2.3 g/kg DM in the control). The levels of neutral detergent fibre and acid detergent fibre were greater (P < 0.001) in S silage than in the control and SL silages, and the hemicellulose level was lower (P = 0.004) in the SL group than the control and S groups. Starch and aerobic stability were unaffected by treatment, and the average lactate and ethanol concentrations were higher (P < 0.001) in the S (53.7 g lactate/kg DM and 28.7 g ethanol/kg DM) and SL (56.9 g lactate/kg DM and 21.4 g ethanol/kg DM) groups than the control (40.1 g lactate/kg DM and 5.3 g ethanol/kg DM) over 90 days of ensiling. Conclusions Overall, a high-dose inoculum of S. cerevisiae alone or combined with L. plantarum affected the nutritional composition and fermentation traits of maize silage. Implications The inoculation of maize silage with a high dose of S. cerevisiae needs to be performed with caution.

Influence of Energy Beverages on the Surface Texture of Glass lonomer Restorative Materials

BACKGROUND AND OBJECTIVE

The objective of the study was to find whether energy beverages have an erosive effect, leading to a risk in the clinical performance of glass ionomer restorative materials.

AIM

This study evaluated the influence of energy beverages on the surface texture of glass ionomer restorative materials.

MATERIALS AND METHODS

Glass ionomer materials used were Ionofil Plus AC, GC EQUIA, and Ketac Molar; energy beverages are Code Red, Red Bull, and Power Horse. Specimens prepared were discs of 8 mm diameter and 3 mm thickness; specimens from each material were evaluated following aging with Code Red, Red Bull, and Power Horse energy beverages. Distilled water was used as a control. The surface roughness (Ra) was assessed by surface scanning interferometry. The surface roughness values (ΔRa and Ra) were measured for each specimen. The data were analyzed statistically using multiple repeated measures [analysis of variance (ANOVA)] and paired data t-test (p < 0.05 was considered as the significance level).

RESULTS

The surface roughness (ΔRa and Ra) values before and after aging using Code Red, Red Bull, and Power Horse energy beverages differ significantly for all the materials regardless of the immersion time (p < 0.05). All the materials showed roughness changes after immersion periods of 1 day, 1 week, and 1 month.

CONCLUSION

It can be concluded that all energy beverage solutions used in this study had an adverse effect on the surface roughness degradation of the tested glass ionomers with increasing immersion time.

CLINICAL SIGNIFICANCE

Energy beverages have an erosive effect on glass ionomer, which influences the clinical importance of the material; it also has anticarious property because it releases the fluoride.

Simultaneous consumption of pentose and hexose sugars: an optimal microbial phenotype for efficient fermentation of lignocellulosic biomass

Lignocellulosic biomass is an attractive carbon source for bio-based fuel and chemical production; however, its compositional heterogeneity hinders its commercial use. Since most microbes possess carbon catabolite repression (CCR), mixed sugars derived from the lignocellulose are consumed sequentially, reducing the efficacy of the overall process. To overcome this barrier, microbes that exhibit the simultaneous consumption of mixed sugars have been isolated and/or developed and evaluated for the lignocellulosic biomass utilization. Specific strains of Escherichia coli, Saccharomyces cerevisiae, and Zymomonas mobilis have been engineered for simultaneous glucose and xylose utilization via mutagenesis or introduction of a xylose metabolic pathway. Other microbes, such as Lactobacillus brevis, Lactobacillus buchneri, and Candida shehatae possess a relaxed CCR mechanism, showing simultaneous consumption of glucose and xylose. By exploiting CCR-negative phenotypes, various integrated processes have been developed that incorporate both enzyme hydrolysis of lignocellulosic material and mixed sugar fermentation, thereby enabling greater productivity and fermentation efficacy.

Relaxed control of sugar utilization in Lactobacillus brevis

Prioritization of sugar consumption is a common theme in bacterial growth and a problem for complete utilization of five and six carbon sugars derived from lignocellulose. Growth studies show that Lactobacillus brevis simultaneously consumes numerous carbon sources and appears to lack normal hierarchical control of carbohydrate utilization. Analysis of several independent L. brevis isolates indicated that co-utilization of xylose and glucose is a common trait for this species. Moreover, carbohydrates that can be used as a single carbon source are simultaneously utilized with glucose. Analysis of the proteome of L. brevis cells grown on glucose, xylose or a glucose/xylose mixture revealed the constitutive expression of the enzymes of the heterofermentative pathway. In addition, fermentative mass balances between mixed sugar inputs and end-products indicated that both glucose and xylose are simultaneously metabolized through the heterofermentative pathway. Proteomic and mRNA analyses revealed that genes in the xyl operon were expressed in the cells grown on xylose or on glucose/xylose mixtures but not in those grown on glucose alone. However, the expression level of XylA and XylB proteins in cells grown on a glucose/xylose mixture was reduced 2.7-fold from that observed in cells grown solely on xylose. These results suggest that regulation of xylose utilization in L. brevis is not stringently controlled as seen in other lactic acid bacteria, where carbon catabolite repression operates to prioritize carbohydrate utilization more rigorously.

Contribution of Gal- lactic acid bacteria to Saccharomyces cerevisiae metabolic activity in milk

The contemporaneous presence of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus affected the growth kinetics of Saccharomyces cerevisiae PZ2 and the metabolic products of their growth were quantitatively and qualitatively different from those produced by single strains inoculated alone. S. cerevisiae can grow in milk without using lactose or galactose. In particular, the presence of peptides seems to be sufficient to ensure its growth. The growth of S. cerevisiae with lactic acid bacteria is characterised by stimulatory effects that involve both yeast and bacteria. However, the release of galactose by lactic acid bacteria does not seem to be the core metabolic event of these stimulatory effects on S. cerevisiae.

Phenotypic and genotypic diversity of yeasts isolated from water-buffalo Mozzarella cheese

Water-buffalo Mozzarella (WBM) cheese is one of the several 'pasta filata' or stretched curd cheeses that originated in southern Italy, traditionally manufactured from raw milk employing natural whey starter cultures. Lactose- and galactose-fermenting yeasts isolated from WBM were studied to evaluate their role in the ripening of this cheese. The kinetic parameters of the growth of the yeasts as well as their principal metabolic end-products showed a great variability depending on the species. Moreover, the genetic polymorphism of the yeasts was studied for their differentiation at species level by means of the polymerase chain reaction (PCR) fingerprinting and mitochondrial DNA (mtDNA) restriction analysis. While the differentiation based on metabolic traits was not able to discriminate Kluyveromyces marxianus, Candida kefyr and C. sphaerica, the PCR analysis with primers M13 and RF2 resulted in a reliable and rapid method for differentiating at species level Saccharomyces cerevisiae, K. marxianus, K. lactis and their anamorphic species. Furthermore, mtDNA analysis proved to be more discriminating at strain level.