Yeast mannoprotein characterization and their effect on Oenococcus oeni and malolactic fermentation
Mannoproteins are released at the end of alcoholic fermentation due to yeast autolysis . It has been described a positive effect of these molecules on lactic acid bacteria growth . The main objective of this work was the characterization of different mannoproteins extracted from active dry yeast (ADY) and the assessment of their effect on Oenococcus oeni and malolactic fermentation (MLF).
The cell wall fraction of strains from different yeast species were extracted by autolysis and alkali methods: Saccharomyces cerevisiae, Torulaspora delbrueckii, Lachancea thermotolerans and Metschnikowia pulcherrima. The profiles of the polysaccharide fraction were analyzed by HPLC-DAD and HRSEC-RID. The protein and glycoprotein profiles were analyzed by SDS-PAGE. The effect on MLF of the addition of 2 g/L of each mannoprotein extract was evaluated in a wine like-medium using the O. oeni strain PSU-1 (ATCC BAA-331). The consumption of L-malic was monitored by an enzymatic method. The analysis of mannoprotein consumption, in terms of equivalents of mannose, was carried out by HPLC-MWC-RID.
The polysaccharide composition and the size of mannoproteins extracted by the two methods were significantly different for all the mannoproteins. Protein and glycoprotein profiles were also different in all the studied yeast walls. The addition of mannoprotein extract influenced the evolution of MLF differently according to the extraction method. Mannoproteins obtained by the yeast autolysis showed a positive effect on MLF in all cases; this effect was also observed in two S. cerevisiae and L. thermotolerans extracted by the alkali method. However, MLF was arrested after consuming 0.5 g/L of L-malic acid in the rest of fermentations with mannoproteins obtained by the alkali method. The results obtained indicate that the capacity of O. oeni to use mannoproteins depends on the mannoprotein composition, which in turns depends on the yeast species and the extraction method.
Keywords: Malolactic fermentation, mannoproteins, Oenococcus oeni
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Issue: ICGWS 2023
1a Grupo de Biotecnología Enológica, 1bGrupo de Biotecnología Microbiana de los Alimentos, Departamento de Bioquímica y Biotecnología, Universitat Rovira i Virgili, Tarragona, España
2 Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Farmacia, Universidad de Salamanca, España