Phenotypic characterization of indigenous Saccharomyces cerevisiae strains associated with sorghum beer and palm wines.

In order to phenotypically characterized Saccharomyces cerevisiae strains isolated from sorghum beer and palm wines for a possible selection of a starter culture, 30 strains were tested for killer activity, temperature resistance, ethanol tolerance, carbohydrate fermentation, enzyme profile and sorghum wort fermentation. Of the tested strains, three showed a killer profile, while four showed a neutral profile and 23 were found to be sensitive to K2 toxin. Temperatures of 40 °C and 44 °C allowed to distinguish strains into four thermal groups with only three strains may grow at 44 °C. Almost tested strains were tolerant to 5% ethanol with viability rates up to 73%. But at 10% and 15% ethanol, respectively 18 and 7 strains were tolerant. Carbohydrate fermentation revealed 13 fermentation profiles, including one typical and 12 atypical profiles. The typical profile strains (16.13% of the strains) fermented glucose, galactose, fructose, sucrose, maltose, trehalose and raffinose. Most of the strains secreted lipases (mainly esterase and esterase-lipase), proteases (mainly valine and cysteine arylamidase, chrymotrypsin) and phosphatases (mainly acid phosphatase and naphthol phosphohydrolase). On contrary, only five strains isolated from sorghum beer exhibited glucosidase activity, mainly α-glucosidase. The analyse of fermented sorghum wort revealed that fermentative performance is strain dependent. Furthermore, the Hierarchical Cluster Analysis showed that the strains were separated in three distinct clusters with the strains from sorghum beer clustered separately.

Candida species in tchapalo and bangui, two traditional alcoholic beverages from Côte d'Ivoire.

The increase of infections due to non-Candida albicans species made it very necessary to conduct adequate characterization to be able to identify the species of Candida isolated from traditional fermented foods. In this study, based on their hue on Candida Chromogenic Agar medium, a total of 136 yeast strains were isolated from tchapalo and bangui. Molecular identification based on PCR-RFLP of internal transcribed spacers of rDNA (ITS) and sequencing of the ITS and the D1/D2 regions allowed us to assign these isolates to seven species: Candida tropicalis, Candida inconspicua, Candida rugosa, Saccharomyces cerevisiae, Kluyveromyces marxianus, Hanseniaspora guilliermondii, Trichosporon asahii. With the respect to each beverage, six species were found among with four species are regarded as opportunistic pathogens. From these, C. tropicalis, C. inconspicua and K. marxianus were the most commonly encountered. The enzyme activities of the potential pathogens assessed using API ZYM system showed that almost strains had esterase, esterase lipase, valine and cystine arylamidase, alpha chymotrypsin, alkaline phosphatase and naphthol phosphohydrolase activities. The activity of α-glucosidase was found only in C. tropicalis and C. inconspicua strains isolated from tchapalo while ß-glucosidase activity was found in all strains from tchapalo and only in C. inconspicua isolated from bangui.