Abstract

ABSTRACT

This study illustrates the stress tolerance levels of locally sourced yeast for vinification. Candida tropicalis^(H4) and Clavispora lusitaniae^(H7) isolated from honey; Candida tropicalis^(B10) and Candida tropicalis^(B7) isolated from banana using standard mycological methods and Candida tropicalis^(CY), a commercial wine yeast, were subjected stress tolerance at various percentages of ethanol (v/v), glucose, sucrose, fructose, metabisulphite (w/v) and pH. The decreasing order of the optimal stress tolerance of yeasts for ethanol was H4 (0.56 OD, 25%) > B7 (0.56 OD, 20%) > B10 (0.58 OD, 20%) and H7 (0.50 OD, 15%) > CY (1.07 OD, 10%); Glucose tolerance, B10 (1.24 OD, 30%) > B7 (1.07 OD, 30%) > CY (1.01 OD, 30%) > H4 (1.07 OD, 25%) > H7 (1.06 OD, 20%); Sucrose tolerance, H4 (1.46 OD, 30%) > B10 (1.23 OD, 30%) > CY (1.17 OD, 30%) > H7 (1.08 OD, 30%) > B7 (1.04 OD, 25%); fructose tolerance, CY (1.636 OD, 20 %) > B10 (1.648 OD, 20 %) > B7 (1.089 OD, 5 %) > H4 (1.362 OD, 10 %) > H7 (1.124 OD, 5%) >B7 (1.089 OD, 5 %); pH tolerance,  B7 and B10 (1.22)  > H7 (1.21)  > CY (1.12)  > H4 (0.73) (OD) at pH 2. Metabisulphite tolerance, H4 (0.68 OD, 0.3g/100ml) > B10 (0.63 OD, 0.3g/100ml) > B7 (0.52 OD, 0.3g/100ml) > CY (0.68 OD, 0.25g/100ml) > H7 (0.56 OD, 0.25g/100ml). The wild non-Saccharomyces isolates possess stress tolerance ability.