Hanseniaspora in wine-making: their genetic modification and potential role in acid modulation

Abstract

Hanseniaspora spp. are one of the most common yeast isolates in vineyards and wineries and play an important role in wine-making.  We explored the impact of an apiculate yeast Hanseniaspora occidentalis strain as a co-partner with Saccharomyces cerevisiae in a sequential-type mixed-culture fermentation of Muscaris grape must.  Like with other fermentation trials using Hanseniaspora strains, a significant increase in ethyl acetate was observed, but most intriguing, was the almost complete abolition of malic acid in the wine.  Compared to the pure S. cerevisiae inoculum there was also a marked increase in the concentrations of the other acetate esters. Modulation of some of the varietal elements like rose oxide was also observed.  Identifying and confirming the genes involved in malic acid utilization and aroma formation would require the development of gene modification tools: a feature not existing yet in H. occidentalis. We have recently developed gene-modifying tools in Hanseniaspora uvarum where we knocked-out the two alleles of the alcohol acetyltransferase gene (HuATF) resulting in a yeast with much lower acetate ester capabilities. This was the first successful attempt to genetically remove a gene from Hanseniaspora and paves the way for further gene-to-function studies in this apiculate yeast
genus