Fungal dynamic during apricot wine spontaneous fermentation and aromatic characteristics of Pichia kudriavzevii for potential as starter.

Microbial activity during spontaneous fermentation in alcoholic beverages have driven in developing the chemical and aromatic characteristic of products but not clear in apricot wines. We have characterised the composition of fungal communities and volatile metabolites in apricot wine spontaneous fermentation among two Shaanxi regions. Results showed that Aureobasidium, Alternaria, Pichia and Saccharomyces, were the dominant fungi in apricot wine fermentation. A total of 80 volatiles including esters, alcohols, acids and terpenes were detected from two apricot wines. Their correlations suggested that apricot wine aroma was mainly affected by Pichia kudriavzevii, rather than Saccharomyces cerevisiae we commonly considered. Furthermore, reinforced inoculation of P. kudriavzevii LQD20 has exhibited the commendable potential in enhancing sensory qualities. The results of this study provide fundamental information of the indigenous microbiota in microbial dynamic during apricot wine fermentation, which would be helpful in exploiting the strains with potential for industrial use as starter cultures.

Microbial diversity on grape epidermis and wine volatile aroma in spontaneous fermentation comprehensively driven by geography, subregion, and variety.

On their journey from the wine grape to the resulting wine, microbiota from grape surfaces controlled by multiple factors is transferred to wine spontaneous fermentation process with indisputable consequences for wine quality parameters. The associated microbiota was regionally distinct (defined to microbial terroir) but how these microbial patterns with significantly regional distinctiveness quantitatively drive the wine regional characteristics are not definite within a complete grape ecosystem at different geographical (> 300 km), subregional (< 10 km), and varietal scales. Here, we collected 24 samples (containing two grape varieties) from four subregions of two regions in Xinjiang wine production area to investigate fungal distribution patterns and the association with wine chemical composition at different evaluation scales. Meanwhile, the relationships were established between geographical, subregional, varietal community of fungi, and wine volatile aroma using partial least squares regression (PLSR) and structural equation modeling (SEM). Results show that microbial and volatile samples present the significantly regional difference inside the complete ecosystem. Microbiota showed a stronger heterogeneity at geography scales, which drove the distributions of subregional and varietal microbiota thereby influencing the volatile composition of finished wines. Moreover, geographical microbiota seems to weaken the effects of varietal community on wine aroma compounds. Microbial communities respond to environmental changes within a completely set grape-related ecosystem at different scales, and these responses resulted in the wine regional distinctiveness based on the volatile profiles. Our findings further confirmed the important role of microbial terroir in shaping wine styles and provided the new cerebration for the terroir drivers of microbiota.

Phenylalanine Promotes Biofilm Formation of Meyerozyma caribbica to Improve Biocontrol Efficacy against Jujube Black Spot Rot.

During storage and transportation after harvest, the jujube fruit is susceptible to black spot rot, which is caused by Alternaria alternata. The present study aimed to evaluate the effectiveness of the yeast Meyerozyma caribbica in controlling A. alternata in postharvest jujube fruits, and to explore the biofilm formation mechanism. The results showed that M. caribbica treatment significantly reduced the A. alternata decay in jujube fruits. M. caribbica could rapidly colonize jujube fruit wounds, adhering tightly to hyphae of A. alternata, and accompanied by the production of extracellular secretions. In in vitro experiments, we identified that M. caribbica adhered to polystyrene plates, indicating a strong biofilm-forming ability. Furthermore, we demonstrated that M. caribbica can secrete phenylethanol, a quorum sensing molecule which can affect biofilm development. Phenylalanine (a precursor substance for phenylethanol synthesis) enhanced the secretion of phenylethanol and promoted the formation of M. caribbica biofilms. Meanwhile, phenylalanine enhanced the biological control performance of M. caribbica against jujube black spot rot. Our study provided new insights that enhance the biological control performance of antagonistic yeast.

Debaryomyces nepalensis reduces fungal decay by affecting the postharvest microbiome during jujube storage.

Microbial antagonists are effective and environmentally friendly in controlling postharvest diseases of fruit. The present study investigated the influence of D. nepalensis on epiphytic microbiome and postharvest decay of jujube. Results showed that D. nepalensis notably reduced fungal decay, maintained the fruit firmness and delayed discoloration. The epiphytic microbiome revealed that D. nepalensis changed the fungal communities, but few influence on bacterial communities were observed. D. nepalensis, as the dominant population in the treatment group, decreased the abundance of pathogenic fungi of Alternaria, Penicillium, Fusarium and Botrytis, while increased the beneficial bacteria of Pantoea. The canonical correspondence analysis revealed that Debaryomyces was negatively correlated with the decay rate, whereas Penicillium, Acremonium, Rhodosporidiobolus and Hansfordia were positively correlated. In conclusion, D. nepalensis altered the successional process of fungal and bacterial communities to reduce the decay rate of jujube during storage.