Phenotypic and genomic differences among S. cerevisiae strains in nitrogen requirements during wine fermentations

Nitrogen requirements by S. cerevisiae during wine fermentation are highly strain-dependent. Different approaches were applied to explore the nitrogen requirements of 28 wine yeast strains. Based on the growth and fermentation behaviour displayed at different nitrogen concentrations, high and low nitrogen-demanding strains were selected and further verified by competition fermentation. Biomass production with increasing nitrogen concentrations in the exponential fermentation phase was analysed by chemostat cultures. Low nitrogen-demanding (LND) strains produced a larger amount of biomass in nitrogen-limited synthetic grape musts, whereas high nitrogen-demanding (HND) strains achieved a bigger biomass yield when the YAN concentration was above 100 mg/L. Constant rate fermentation was carried out with both strains to determine the amount of nitrogen required to maintain the highest fermentation rate. Large differences appeared in the analysis of the genomes of low and high-nitrogen demanding strains showed for heterozygosity and the amino acid substitutions between orthologous proteins, with nitrogen recycling system genes showing the widest amino acid divergences. The CRISPR/Cas9-mediated genome modification method was used to validate the involvement of GCN1 in the yeast strain nitrogen needs. However, the allele swapping of gene GCN1 from low nitrogen-demanding strains to high nitrogen-demanding strains did not significantly influence the fermentation rate.The authors thank Lallemand Inc. For supplying the strains and funding the project. This project has been also partially funding by the grants GRISOLIA/2015/030 and PROMETEO/2020/014, both from Generalitat Valenciana, awarded to YS and AQ respectively.Peer reviewe