# Genetic, Physiological, and Industrial Aspects of the
## 3 _S. bacillaris_ Physiology
Furthermore, phylogenetic and kinetic analyses of putative alcohol dehydrogenase proteins, Adh1 and Adh6, present in the genomes of W/S-clade species, revealed that the corresponding _ADH1_ and _ADH6_ genes seem to have been horizontally transferred from bacteria [30]. Ethanol production in members of the W/S clade, conducted by alcohol dehydrogenases of bacterial origin, allow W/S clade species to maintain redox homeostasis (i.e., NAD+ regeneration) when growing under anaerobic conditions [30]. _S. bacillaris_, in particular, harbors one copy of an _ADH1_ xenolog; the _ADH6_ xenolog was apparently duplicated several times, as this yeast species harbors four _ADH6_ paralogs [30]. _S. bacillaris_ uses higher sugar quantities (i.e., up to 40 g/L) than _S. cerevisiae_ to produce 1% (_v/v_) ethanol [7; 23; 50; 57]. This low ethanol yield, in addition to its low acetic acid production, of _S. bacillaris_ compared to _S. cerevisiae_, reveals low activity of the acetaldehyde pathway in _S. bacillaris_, leading to a redistribution in the fluxes of the central carbon metabolism network [58]. Differently from other members of the W/S clade, which convert fructose directly into mannitol [31], _S. bacillaris_ overproduces glycerol to maintain the  
Figure 3: _S. bacillaris_ colony morphology. Colonies of _C. zemplinina_ (syn., _S. bacillaris_) strain CBS 9494 as observed in standard YPD (**a**) or differential WL-nutrient agar media (**b**), after incubation during 72 h at 25 \({}^{\circ}\)C. _S. bacillaris_ forms small pale green, creamy colonies in WL-nutrient agar (**b**). “Multi-species” reconstitution experiment of common non-_Saccharomyces_ yeasts (_Hansenispora uavrum, Pichia membranitaciens, Metschnikowia pulcherrina_, and _Tortulspora delbrueckii_), _S. cerevisiae_ (strain EC1118), and _C. zemplinina_ (strain CBS 9494) (**c**). The photography shows the particular morphology and color aspects, on WL-nutrient agar, of the various plated yeast species [49]. Bar in (**c**) represents 1 mm. Identical magnification for all colonies is shown. _S. bacillaris_ (_C. zemplinina_ CBS 9494; _Cz_) is resistant to cycloheximide (**d–f**), a phenotype that allows selective recognition of indigenous non-_Saccharomyces_ compared to cycloheximide-sensitive _S. cerevisiae_ strains (_Sc_) [20]. NADH/NAD+ redox balance in the cells [31; 58]. Thus, high glycerol levels are frequently reported for fermentations involving this yeast species [17; 58; 59; 60; 61]. Interestingly, different levels of glycerol production may be associated with alternative alleles of the _GPP1_ gene, encoding glycerol-3-phosphate phosphatase [29]. A reduced lag phase has been observed in _S. bacillaris_ strains growing under low nitrogen conditions, suggesting a limited nitrogen requirement of this yeast species [51]. A preferential uptake of ammonium, tryptophan, and arginine, versus other poorly assimilated amino acids, has been observed in fermenting _S. bacillaris_ cells [62]. The consumption of nitrogen sources by _S. bacillaris_ revealed the strong inability of this species to take up most amino acids in the presence of ammonium [62]. However, nitrogen provided as ammonium versus a mixture of amino acids showed that organic nitrogen compounds supported more efficiently the growth of _S. bacillaris_[62]. Extracellular enzymes produced by _S. bacillaris_ include \(\beta\)-glucosidase [50], proteases [26; 50], and chitinases [26]. No pectinase, xylanase, lipase, or cellulase activities have yet been reported. The production of these enzymes may be finally dependent on the analyzed strain, the composition of the growing media, and/or the growth conditions [50]. For specific fermentation processes, it may be important to perform a detailed characterization of the extracellular enzymes secreted by _S. bacillaris_, to determine the final chemical profile of wines and/or to use this species as a biocontrol agent [26; 27]. Subtle but significant differences have been observed for the various metabolic fermentative traits of _S. bacillaris_ strains [16; 17; 50].