Phenotypic and genomic assessment of sugar assimilation in the pomegranate yeast Hanseniaspora valbyensis

Among non-conventional yeasts, Hanseniaspora is known for its high capacity to produce aroma compounds during fermentation and for its apparent reduced ability to completely utilise sugars in some ecosystems, due to sensitivity to ethanol or antimicrobials produced by other yeasts. Although the capacity of Hansenisapora species (e.g. Hanseniaspora valbyensis) to grow on fructose was previously reported, no fructose-specific transporters were identified. This study aimed to characterize fermentation behavior and scout potential fructose transporters of H. valbyensis biotypes, isolated from pomegranate. Well characterised strains of Saccharomyces cerevisiae and Kluyveromyces marxianus were used as references. The capacity to assimilate diverse sugars was first assessed using agar minimal medium (MM) supplemented (at 2 %) with glucose, fructose, lactose, xylose, maltose, or sucrose. H. valbyensis grew at highest level on MM plates containing glucose or fructose. Starting from this result, growth, sugar consumption and metabolite production were investigated during liquid cultivation on glucose, fructose, glucose and fructose. Among the yeast species under investigation, only H. valbyensis was able to consume fructose and glucose after cultivation on MM broth, thus suggesting potential fructophilic behavior. Whole genome analysis was performed to identify potential sugar transporters of H. valbyensis, and a phylogenetic tree was built. The analysis showed that some sugar transporters of H. valbyensis were close to Ffz1 fructose facilitator of Zygosaccharomyces bailii. Ffz transporters are phylogenetically distinct from all the other previously characterized hexose transporters and more similar to drug transporters. Further research will focus on the role of this candidate Ffz1-like transporter in H. valbyensis.