Use of non-Saccharomyces yeasts in cider fermentation: Importance of the nutrients addition to obtain an efficient fermentation

Kinetic Evaluation of the Production of Mead from a Non-Saccharomyces Strain

There is a growing market for craft beverages with unique flavors. This study aimed to obtain a palate-pleasing mead derived from Pichia kudriavzevii 4A as a monoculture. Different culture media were evaluated to compare the fermentation kinetics and final products. The crucial factors in the medium were ~200 mg L-1 of yeast assimilable nitrogen and a pH of 3.5-5.0. A panel of judges favored the mead derived from Pichia kudriavzevii 4A (fermented in a medium with honey initially at 23 °Bx) over a commercial sample produced from Saccharomyces cerevisiae, considering its appearance, fruity and floral flavors (provided by esters, aldehydes, and higher alcohols), and balance between sweetness (given by the 82.91 g L-1 of residual sugars) and alcohol. The present mead had an 8.57% v/v ethanol concentration, was elaborated in 28 days, and reached a maximum biomass growth (2.40 g L-1) on the same fermentation day (6) that the minimum level of pH was reached. The biomass growth yield peaked at 24 and 48 h (~0.049 g g-1), while the ethanol yield peaked at 24 h (1.525 ± 0.332 g g-1), in both cases declining thereafter. The Gompertz model adequately describes the kinetics of sugar consumption and the generation of yeast biomass and ethanol. Pathogenic microorganisms, methanol, lead, and arsenic were absent in the mead. Thus, Pichia kudriavzevii 4A produced a safe and quality mead with probable consumer acceptance.

Valorization of Cashew Apple Waste into a Low-Alcohol, Healthy Drink Using a Co-Culture of Cyberlindnera rhodanensis DK and Lactobacillus pentosus A14-6

This study investigated the potential of microbial fermentative transforming processes in valorizing the cashew apple by-product into a low-alcohol, health-benefiting beverage. We particularly investigated the use of a non-Saccharomyces yeast, Cyberlindnera rhodanensis DK, as the main targeted microbe. At 30 °C without agitation, C. rhodanensis DK caused changes in key parameters during the fermentation of cashew apple juice (CAJ) in terms of varied pH values and initial sugar concentrations. This result indicated that pure CAJ, with pH adjusted to 6 and with the original 6.85% (w/v) total sugar content, was the most feasible condition, as glucose and fructose were mostly consumed at 12 days of fermentation. A co-culture approach with either Saccharomyces cerevisiae TISTR 5088 or Lactobacillus pentosus A14-6 was investigated to improve both physicochemical and fermentation characteristics. Co-fermentation with S. cerevisiae TISTR 5088 resulted in significantly increased ethanol accumulation to 33.61 ± 0.11 g/L, but diminished bioactive compounds, antioxidant activity, and antidiabetic potential. In contrast, co-fermentation with L. pentosus A14-6 demonstrated excellent outcomes, as it significantly increased sugar consumption and finally remained at only 4.95 g/L compared to C. rhodanensis DK alone, produced lower levels of ethanol at only 19.47 ± 0.06 g/L, and higher total titratable acid (TTA), resulting in a final pH of 3.6. In addition, co-fermentation with this lactic acid bacterium significantly enhanced bioactive compounds and antioxidant activity and also retained potential antidiabetic properties. These findings highlight the feasibility of using tailored microbial fermentation strategies to produce low-alcohol beverages with enhanced health-promoting properties from CAJ; however, product-development processes following health food regulations and sensory evaluation are necessary.

A catalog of ethanol-producing microbes in humans

Aim: Endogenous ethanol production emerges as a mechanism of nonalcoholic steatohepatitis, obesity, diabetes and auto-brewery syndrome. Methods: To identify ethanol-producing microbes in humans, we used the NCBI taxonomy browser and the PubMed database with an automatic query and manual verification. Results: 85 ethanol-producing microbes in human were identified. Saccharomyces cerevisiae, Candida and Pichia were the most represented fungi. Enterobacteriaceae was the most represented bacterial family with mainly Escherichia coli and Klebsiella pneumoniae. Species of the Lachnospiraceae and Clostridiaceae family, of the Lactobacillales order and of the Bifidobacterium genus were also identified. Conclusion: This catalog will help the study of ethanol-producing microbes in human in the pathophysiology, diagnosis, prevention and management of human diseases associated with endogenous ethanol production.

A comparative study of the effect of bacteria and yeasts communities on inoculated and spontaneously fermented apple cider

Understanding bacteria and yeasts communities can reduce unpredictable changes of apple cider. In this study, apple juice inoculated with Saccharomyces cerevisiae WET 136 and fermented spontaneously were compared, the relationships of bacteria, yeasts, organic acids, and volatiles were analyzed. Results showed that microbial diversity affected the fermentation, organic acids and volatiles in apple ciders. In the first four spontaneous fermentation days, LAB (lactic acid bacteria) multiplied and reached 7.89 lg CFU/mL, and then triggered malolactic fermentation (MLF), leading to malic acid decreased by 3880.52 mg/L and lactic acid increased by 4787.55 mg/L. The citric, succinic and fumaric acids content was 2171.14, 701.51 and 8.06 mg/L lower than that in inoculated cider, respectively. Although the yeasts multiplied during spontaneous fermentation, it did not reach 7.50 lg CFU/mL until the 5th day, which led to a long lag period, as well as later and lower production of acetaldehyde and higher alcohols. The inoculated yeast inhibited LAB, acetic acid bacteria, Rahnella, and non-Saccharomyces. Yeasts were the key to produce citric acid, acetaldehyde and 3-methyl-1-butanol in apple cider; while bacteria were closely related to the formation of lactic acid, acetic acid and ethyl acetate. It suggested that low higher alcohols and acetaldehyde can be realized by selecting yeasts, and Leuconostoc pseudomesenteroides can work as candidate to reduce L-malic and citric acids in apple cider.

Quality Improvement in Apple Ciders during Simultaneous Co-Fermentation through Triple Mixed-Cultures of Saccharomyces cerevisiae, Pichia kudriavzevii, and Lactiplantibacillus plantarum

This study explored the effect of the combination of Saccharomyces yeast, non-Saccharomyces yeast (Pichia kudriavzevii), and Lactiplantibacillus plantarum during cider fermentation on physicochemical properties, antioxidant activities, flavor and aroma compounds, as well as sensory qualities. Ciders fermented with the triple mixed-cultures of these three species showed lower acid and alcohol content than those fermented with the single-culture of S. cerevisiae. The antioxidant activities were enhanced by the triple mixed-culture fermentation, giving a higher 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate and total antioxidant capacity; specifically, the SPL5 cider showed the highest DPPH radical scavenging rate (77.28%), while the SPL2 gave the highest total antioxidant capacity (39.57 mmol/L). Additionally, the triple mixed-culture fermentation resulted in improved flavor and aroma with a lower acidity (L-malic acid) and higher aroma compounds (Esters), when compared with the single-culture fermented ciders (Saccharomyces cerevisiae); more specifically, the SPL4 cider resulted in the highest total flavor and aroma compounds. In addition, sensory evaluation demonstrated that ciders produced using the triple mixed-cultures gained higher scores than those fermented using the single-culture of S. cerevisiae, giving better floral aroma, fruity flavor, and overall acceptability. Therefore, our results indicated that the triple mixed-cultures (S. cerevisiae, P. kudriavzevii, and L. plantarum) were found to make up some enological shortages of the single S. cerevisiae fermented cider. This study is believed to provide a potential strategy to enhance cider quality and further give a reference for new industrial development protocols for cider fermentation that have better sensory qualities with higher antioxidant properties.

Comparative metabolome and transcriptome analyses of the properties of Kluyveromyces marxianus and Saccharomyces yeasts in apple cider fermentation

This study explored the application of Kluyveromyces marxianus and Saccharomyces cerevisiae (commercial and wild type) in the alcoholic fermentation of Fuji apple juice under static conditions. Metabolome analyses revealed that ethyl esters, including ethyl hexanoate, ethyl decanoate, ethyl octanoate, octanoic acid and decanoic acid, were the dominant components in ciders fermented by the Saccharomyces yeasts. In the K. marxianus ciders, ethyl acetate, hexyl acetate, propyl acetate and acetic acid were the most abundant volatiles, suggesting that the cider fermented by K. marxianus might have a fruitier smell. Transcriptome analyses were adapted to gain insight into the differential metabolite patterns between K. marxianus and S. cerevisiae during cider fermentation. GO and KEGG enrichments revealed that the metabolic pathways of glucose, organic acids and amino acids during cider fermentation were quite different between these two yeasts. The K. marxianus strain exhibited a higher rate of glycolysis and ethanol fermentation than did Saccharomyces yeasts under oxygen-limited conditions. It also reduced the metabolic flux of acetate into acetyl-CoA and then into the TCA cycle, increasing the syntheses of ethyl acetate and relevant esters, which may affect its cell growth under anaerobic conditions but enriched the taste and variety of aromas in apple cider.

Chemical and Sensory Characteristics of Fruit Juice and Fruit Fermented Beverages and Their Consumer Acceptance

Recent social, economic, and technological evolutions have impacted consumption habits. The new consumer is more rational, more connected and demanding with products, more concerned with the management of the family budget, with the health, origin, and sustainability of food. The food industry over the last few years has shown remarkable technological and scientific evolution, with an impact on the development and innovation of new products using non-thermal processing. Non-thermal processing technologies involve methods by which fruit juices receive microbiological inactivation and enzymatic denaturation with or without the direct application of low heat, thereby lessening the adverse effects on the nutritional, bioactive, and flavor compounds of the treated fruit juices, extending their shelf-life. The recognition of the nutritional and protective values of fruit juices and fermented fruit beverages is evident and is attributed to the presence of different bioactive compounds, protecting against chronic and metabolic diseases. Fermentation maintains the fruit's safety, nutrition, and shelf life and the development of new products. This review aims to summarize the chemical and sensory characteristics of fruit juices and fermented fruit drinks, the fermentation process, its benefits, and its effects.

Screening and Identification of Yeasts from Fruits and Their Coculture for Cider Production

Coculturing non-Saccharomyces yeasts with Saccharomyces cerevisiae could enrich the aromatic complexity of alcoholic beverages during cider brewing. Therefore, the present study performed rapid strain screening via selective culture medium and aroma analysis and adopted a response surface methodology to optimize fermentation conditions to produce 2-phenylethyl acetate (PEA), which presents a rose and honey scent. The effects of coculturing yeasts on cider quality were evaluated through hedonic sensory analysis and the check-all-that-apply (CATA) method. Hanseniaspora vineae P5 and S. cerevisiae P1 produced ciders with high levels of PEA and 2-phenylethanol, respectively. The optimal fermentation process consisted of sequential inoculation with a 31 h delay between inoculations, followed by fermentation for 14.5 d at 18.7 °C, yielding 17.41 ± 0.51 mg/L of PEA, which was 4.6-fold higher than that obtained through the unoptimized fermentation process. Additionally, the CATA results revealed that the cider produced through coculturing was associated with descriptors such as “smooth taste”, “honey”, “pineapple”, and “fruity”, which can be attributed to the high ethyl acetate and PEA levels in the cider.

Coordinately express hemicellulolytic enzymes in Kluyveromyces marxianus to improve the saccharification and ethanol production from corncobs

BACKGROUND

Hemicellulose acts as one factor contributing to the recalcitrance of lignocellulose that prevents cellulases to degrade the cellulose efficiently even in low quantities. Supplement of hemicellulases can enhance the performance of commercial cellulases in the enzymatic hydrolyses of lignocellulose. Kluyveromyce marxianus is an attractive yeast for cellulosic ethanol fermentation, as well as a promising host for heterologous protein production, since it has remarkable thermotolerance, high growth rate, and broad substrate spectrum etc. In this study, we attempted to coordinately express multiple hemicellulases in K. marxianus through a 2A-mediated ribosome skipping to self-cleave polyproteins, and investigated their capabilities for saccharification and ethanol production from corncobs.

RESULTS

Two polycistronic genes IMPX and IMPαX were constructed to test the self-cleavage of P2A sequence from the Foot-and-Mouth Disease virus (FMDV) in K. marxianus. The IMPX gene consisted of a β-mannanase gene M330 (without the stop codon), a P2A sequence and a β-xylanase gene Xyn-CDBFV in turn. In the IMPαX gene, there was an additional α-factor signal sequence in frame with the N-terminus of Xyn-CDBFV. The extracellular β-mannanase activities of the IMPX and IMPαX strains were 21.34 and 15.50 U/mL, respectively, but the extracellular β-xylanase activity of IMPαX strain was much higher than that of the IMPX strain, which was 136.17 and 42.07 U/mL, respectively. Subsequently, two recombinant strains, the IXPαR and IMPαXPαR, were constructed to coordinately and secretorily express two xylantic enzymes, Xyn-CDBFV and β-D-xylosidase RuXyn1, or three hemicellulolytic enzymes including M330, Xyn-CDBFV and RuXyn1. In fed-batch fermentation, extracellular activities of β-xylanase and β-xylosidase in the IXPαR strain were 1664.2 and 0.90 U/mL. Similarly, the IMPαXPαR strain secreted the three enzymes, β-mannanase, β-xylanase, and β-xylosidase, with the activities of 159.8, 2210.5, and 1.25 U/mL, respectively. Hemicellulolases of both strains enhanced the yields of glucose and xylose from diluted acid pretreated (DAP) corncobs when acted synergistically with commercial cellulases. In hybrid saccharification and fermentation (HSF) of DAP corncobs, hemicellulases of the IMPαXPαR strain increased the ethanol yield by 8.7% at 144 h compared with the control. However, both ethanol and xylose yields were increased by 12.7 and 18.2%, respectively, at 120 h in HSF of aqueous ammonia pretreated (AAP) corncobs with this strain. Our results indicated that coordinate expression of hemicellulolytic enzymes in K. marxianus promoted the saccharification and ethanol production from corncobs.

CONCLUSIONS

The FMDV P2A sequence showed high efficiency in self-cleavage of polyproteins in K. marxianus and could be used for secretory expression of multiple enzymes in the presence of their signal sequences. The IMPαXPαR strain coexpressed three hemicellulolytic enzymes improved the saccharification and ethanol production from corncobs, and could be used as a promising strain for ethanol production from lignocelluloses.