**4. Biotechnological properties of non-***Saccharomyces***: fermentation and assimilation of carbon compounds**

Fermentation of carbon compounds is particularly useful for identifying isolates with new fermentation profiles for potential applications in various fields. The carbon compounds assayed were D-glucose, D-galactose, L-arabinose, L-rhamnose, melibiose, lactose, raffinose, xylose, maltose, mannose, saccharose and cellobiose. The tests were carried out on a 96-well microtiter plate. Each well was filled with sugar solution, bromocresol green and cell suspensions (exhausting the endogenous carbon compound reserves). Finally, the wells were sealed with sterile vaseline, and the plates were incubated at 28°C/5 days. Depending on the time of the change and the intensity of colouration (from blue to yellow or yellow green), a classification system was established [27, 28].

The majority of the isolates (*Torulaspora*, *Lachancea* and *Saccharomycodes* species and *C. lactis-condensi*) fermented D-glucose either in the first 12 h or on the 5th day. D-mannose and saccharose were fermented to a lesser extent.

None of the isolates fermented xylose, lactose, arabinose, melibiose and rhamnose, and some only weakly fermented galactose, maltose and raffinose.

*C. lactis-condensi* fermented the majority of the sugars at a major or minor intensity. On the other hand, for galactose, raffinose and saccharose fermentation, variability was observed in species such as T. *delbrueckii*, *C. lactis-condensi*, *P. galeiformis* and *C. ethanolica*.

Only one *H. uvarum* isolate and one *H. vinae* isolate weakly fermented cellobiose, which is a sugar of great biotechnological interest in the production of bioethanol from agricultural and forest by-products.

The compounds used for the assimilation assay were mono- and disaccharides (D-glucose, maltose, lactose, L-rhamnose, xylose and cellobiose), polysaccharides (starch, carboxymethylcellulose and lignin) and alcohols (ethanol and methanol).

The tests were carried out in agar plates containing the carbon source and YNB without amino acids (Difco™). The assimilation profile was noticed as (++) abundant growth, (+) normal growth and (−) absence of growth.

Assimilation of carbon compounds, glucose and maltose were the most commonly used and, to a lesser extent, xylose and methanol. Three species of *Candida*, *C. viswanathii, C. ethanolica* and *C. sake*, and one *P. galeiformis* isolate assimilated carboxymethyl cellulose, while three *Pichia* isolates used starch. The majority of *Torulaspora* isolates and a few isolates of *P. kudriavzevii*, *P. galeiformis* and *H. osmophila* assimilated xylose. All of the *H. osmophila, H. uvarum* and *S'codes ludwigii* isolates effectively assimilated cellobiose. Ethanol was assimilated by a few *P. galeiformis* and *P. anomala* isolates. Finally, only some *L. thermotolerans, P. kudriavzevii*, *C. sake* and *C. viswanathii* isolates assimilated methanol. Thus, differences between isolates of the same species were observed, as can be seen in the fermentation tests.
