The effects of cell-cell contact between Pichia kluyveri and Saccharomyces cerevisiae on amino acids and volatiles in mixed culture alcoholic fermentations

Lactiplantibacillus plantarum exerts strain-specific effects on malolactic fermentation, antioxidant activity, and aroma profile of apple cider

This study aimed to investigate the impact of different strains of Lactiplantibacillus plantarum on malolactic fermentation (MLF), antioxidant activity, and aroma of ciders. A commercial strain of Saccharomyces cerevisiae and six indigenous L. plantarum strains were co-inoculated into apple juice to induce simultaneous alcoholic fermentation (AF) and MLF. The findings indicated that despite belonging to the same species, the different L. plantarum strains significantly differed (p < 0.05) in terms of antioxidant activity and aroma compounds in the ciders. MLF induced by L. plantarum resulted in the substantial consumption of malic acid and increased levels of lactic acid in the ciders, with strain-specific effects observed, particularly with L. plantarum SCFF284. In addition, ciders produced from mixed fermentations exhibited higher levels of antioxidant activity than those from pure S. cerevisiae fermentation (p < 0.05), especially for LAM284. Furthermore, ciders produced from mixed fermentations exhibited higher levels of aroma compounds, such as ethyl acetate and isoamyl alcohol, and also received higher sensory scores compared to ciders produced through pure S. cerevisiae fermentation (p < 0.05). These results highlight the effectiveness of MLF induced by L. plantarum in enhancing the antioxidant activity and aroma profile of ciders.

Improving aromatic higher alcohol acetates in wines by co-fermentation of Pichia kluyveri and Saccharomyces cerevisiae: growth interaction and amino acid competition

BACKGROUND

Higher alcohol acetates (HAAs) are potent aroma-active esters that impart desirable fruity and floral aromas. However, the conversion of higher alcohol precursors into HAAs is extremely low in winemaking. To investigate the underlying yeast-yeast interaction on targeted improvement of aromatic HAAs, we evaluated fermentation activity, cell viability, amino acid consumption and HAA production when Pichia kluyveri and Saccharomyces cerevisiae were inoculated concurrently or sequentially.

RESULTS

Pichia kluyveri PK-21 possessed the ability to survive and increased HAA level up to 5.2-fold in mixed fermentation. Such an increment may benefit from the efficient conversion of higher alcohol precursors into HAAs (>27-fold higher than S. cerevisiae). During mixed fermentation, the two yeasts exhibited crucial interactions regarding cell growth and amino acid competition. Saccharomyces cerevisiae dominated over the co-inoculated P. kluyveri by efficient uptake of amino acids and biomass production. However, this dominance decreased in sequential fermentation, where P. kluyveri growth increased due to the consumption of preferred amino acids prior to S. cerevisiae. Pearson correlation analysis indicated that phenylalanine and aspartic acid may act as positive amino acids in boosting P. kluyveri growth and HAA production. Laboratory-scale winemaking validated the fermentation performance of P. kluyveri in sequential inoculum, resulting in a balanced aroma profile with enhanced floral and tropical fruity characteristics in the final wines.

CONCLUSION

This study proposes a microbial, non-genetically engineered approach for targeted increase of HAA production in winemaking and the findings provide new insights into yeast-yeast interactions. © 2024 Society of Chemical Industry.

A comparative study to investigate the individual contribution of metabolic and physical interaction on volatiles formation in the mixed fermentation of Torulaspora delbrueckii and Saccharomyces cerevisiae

It is well-known that the co-inoculation of Saccharomyces cerevisiae and non-Saccharomyces strains can modulate and improve the aromatic quality of wine through their multi-level interactions. However, the individual contribution of metabolic interaction (MI) and physical interaction (PI) on wine volatiles remains poorly understood. In this work, we utilized a double-compartment bioreactor to examine the aromatic effect of MI and PI by comparing the volatiles production in Torulaspora delbrueckii and Saccharomyces cerevisiae single fermentations to their mixed fermentations with or without physical separation. Results showed that the PI between T. delbrueckii and S. cerevisiae increased the production of most aroma compounds, especially for acetate esters and volatile fatty acids. In comparison, the MI only promoted a few volatile compounds, including ethyl decanoate, isoamyl acetate, and isobutanol. Noticeably, the MI significantly decreased the levels of ethyl dodecanoate, 2-phenylethyl alcohol, and decanoic acid, which exhibited opposite profiles in PI. Our results indicated that the PI was mainly responsible for the improved volatiles in T. delbrueckii/S. cerevisiae mixed fermentation, while the MI can be targeted to modulate the specific aroma compounds. A thorough understanding of the PI and MI aromatic effect will empower winemakers to accurately and directionally control the volatile profile of the wine, promoting the application of multi-starters to produce diverse styles of wines.

Strain specific Starmerella bacillaris and Saccharomyces cerevisiae interactions in mixed fermentations

AIMS

Yeast interactions have a key role in the definition of the chemical profile of the wines. For this reason, winemakers are increasingly interested in mixed fermentations, employing Saccharomyces cerevisiae and non-Saccharomyces strains. However, the outcome of mixed fermentations is often contradictory because there is a great variability among strains within species. Previously, it was demonstrated that the loss of culturability of Starmerella bacillaris in mixed fermentations with S. cerevisiae was due to the physical contact between cells. Therefore, to further explore previous observations, the interaction mechanisms among different strains of Starm. bacillaris and S. cerevisiae during mixed fermentations were investigated.

METHODS AND RESULTS

Fermentations were conducted under conditions that allow physical contact between cells (flasks) but also using a double-compartment fermentation system in which cells of both species were kept separate. The role of competition for nutrients and antimicrobial compounds production on yeast-yeast interaction mechanisms was also investigated. Three Starm. bacillaris and three S. cerevisiae strains were used to investigate if interaction mechanisms are modulated in a strain-specific way. Both species populations were affected by physical contact, particularly Starm. bacillaris that lost its culturability during fermentation. In addition, loss of culturability of Starm. bacillaris strains was observed earlier in flasks than in the double-compartment system. The phenomena observed occurred in a strain couple-dependent way. Starm. bacillaris disappearance seemed to be independent of nutrient depletion or the presence of inhibitory compounds (which were not measured in this study).

CONCLUSION

Overall, the results of the present study reveal that cell-to-cell contact plays a role in the early death of non-Saccharomyces but the extent to which it is observed depends greatly on the Starm. bacillaris/S. cerevisiae strains tested.

Enhancement of ester biosynthesis in blueberry wines through co-fermentation via cell-cell contact between Torulaspora delbrueckii and Saccharomyces cerevisiae

This study investigated the effects of co-fermentation of T. delbrueckii and S. cerevisiae on the volatile composition and sensory characteristics of blueberry wines. Mixed fermentation led to higher levels of terpenes, higher alcohols, and esters compared to wines fermented with each yeast individually. Conversely, when T. delbrueckii were physically separated from S. cerevisiae in the double-compartment fermenter, contrasting outcomes emerged. The stronger fruity aroma induced by mixed fermentation were linked to higher ester concentrations, including isoamyl acetate, ethyl isovalerate, ethyl hexanoate, and diethyl succinate. The enhanced esters in mixed fermentation can be attributed to the upregulated alcohol acyltransferase activity and the expressions of ACC1, FAS2, ELO1 and ATF1 genes in late fermentation stage via the cell-cell contact between T. delbrueckii and S. cerevisiae. These findings can deepen the understanding of the interaction between non-Saccharomyces and S. cerevisiae in ester production, assisting wineries in effectively controlling wine aroma through mixed fermentations.

Multi-omics analysis reveals the microbial interactions of S. cerevisiae and L. plantarum on Suanyu, Chinese traditional fermented fish

S. cerevisiae and L. plantarum play important roles in Suanyu fermentation. This study investigated the interaction between S. cerevisiae and L. plantarum during fermentation and its impact on metabolic pathways. Co-culturing S. cerevisiae and L. plantarum increased pH to 5.72, reduced TVB-N to 9.47 mg/mL, and achieved high utilization rates of sugars (98.9%) and proteins (73.7%). During microbial interactions, S. cerevisiae and L. plantarum produced antibiotics, including phenyllactate and Gentamicin C1a, inhibiting the growth of each other. S. cerevisiae used S-adenosyl-l-methionine to counteract acid production of L. plantarum, establishing dominance in Suanyu fermentation. Microbial interactions influenced carbohydrate and energy metabolism pathways, such as nicotinate and nicotinamide metabolism and purine metabolism. S. cerevisiae significantly impacted gene expression in protein synthesis and cell growth pathways, including ribosome, SNARE interactions, basal transcription factors, and MAPK signaling. These findings offer insights into microbial interactions and metabolic processes during Suanyu fermentation.

Bio-protection in oenology by Metschnikowia pulcherrima: from field results to scientific inquiry

Finding alternatives to the use of chemical inputs to preserve the sanitary and organoleptic quality of food and beverages is essential to meet public health requirements and consumer preferences. In oenology, numerous manufacturers already offer a diverse range of bio-protection yeasts to protect must against microbiological alterations and therefore limit or eliminate sulphites during winemaking. Bio-protection involves selecting non-Saccharomyces yeasts belonging to different genera and species to induce negative interactions with indigenous microorganisms, thereby limiting their development and their impact on the matrix. Although the effectiveness of bio-protection in the winemaking industry has been reported in numerous journals, the underlying mechanisms are not yet well understood. The aim of this review is to examine the current state of the art of field trials and laboratory studies that demonstrate the effects of using yeasts for bio-protection, as well as the interaction mechanisms that may be responsible for these effects. It focuses on the yeast Metschnikowia pulcherrima, particularly recommended for the bio-protection of grape musts.

Fungal Diversity and Its Relationship with Environmental Factors in Coastal Sediments from Guangdong, China

As one core of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), Guangdong is facing some serious coastal environmental problems. Fungi are more vulnerable to changes in coastal environments than bacteria and archaea. This study investigated the fungal diversity and composition by high-throughput sequencing and detected basic parameters of seven environmental factors (temperature, dissolved oxygen, pH, salinity, total organic carbon, total nitrogen, and total phosphorus) at 11 sites. A total of 2056 fungal operational taxonomic units (OTUs) belonging to 147 genera in 6 phyla were recovered; Archaeorhizomyces (17.5%) and Aspergillus (14.19%) were the most dominant genera. Interestingly, a total of 14 genera represented the first reports of coastal fungi in this study. Furthermore, there were nine genera of fungi that were significantly correlated with environmental factors. FUNGuild analysis indicated that saprotrophs and pathogens were the two trophic types with the highest proportions. Saprotrophs were significantly correlated with total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP), while pathogens were significantly correlated with pH. This study provides new scientific data for the study of the diversity and composition of fungal communities in coastal ecosystems.