Expanding the biotechnological potential of M. pulcherrima/fructicola clade for wine-related applications

Abstract

AIM: Strains belonging to M. pulcherrima/fructicola clade are frequently isolated from flowers, fruits and grape musts, and exhibit a broad spectrum of enzymatic activities and antimicrobial potential (Morata et al., 2019; Sipiczki, 2020; Vicente et al. 2020). By reason of these features, selected strains of this clade have been proposed as non-Saccharomyces starter cultures for winemaking. In this study, with a view to valorise the biotechnological potential of these strains, a new Metschnikowia sp. strain, DBT012, was selected for application in vinification trials of Valpolicella’s fresh and withered typical grapes for reduction of SO₂addition and increase of aromatic complexity. Further, in the framework of the investigation on the biodiversity of a collection of strains, distinct pulcherrimin-producing isolates from spontaneous fermentation and grapes were putatively recognized as Metschnikowia spp. and selected for genotypic and phenotypic characterisation.

METHODS: Lyophilised cultures of the reference strain DBT012 were tested in pilot-scale vinifications (mixed-cultures with S. cerevisiae). The isolates were characterised based on enzymatic activities (e.g., sulphite-reductase and beta-glucosidase activities) and growth under different wine-related stress conditions (e.g., ethanol, high sugar content). Genetic fingerprinting techniques (e.g., (GTG)5 and microsatellite) were performed for de-replication of isolates and strain typing. Whole-genome sequencing of the reference strain was carried out to analyse the correlation between genotype and phenotype, and comparative analyses with available type strains were performed to deepen the taxonomic aspects and molecularly identify this strain.

RESULTS: Use of Metschnikowia sp. DBT012 reduced the acetaldehyde content in wines, and positively influenced the wine aroma. About 50 Metschnikowia strains were characterised, which displayed a significant phenotypic diversity in terms of β-glucosidase and esterase activities, H2S production and growth at high sugar concentrations. The relationship of those features with genotypic and genomic distinctiveness of the reference strain was highlighted.

CONCLUSIONS:

The well-characterised thematic collection of strains belonging to M. pulcherrima/fructicola clade presented here constitutes an important reservoir of biodiversity for applications in different wine-related scenarios.