Diauxic utilization of glucose-cellobiose mixtures by Candida wickerhamii

Abstract

Glucose and cellobiose are the principle sugars released during cellulose hydrolysis. The utilization of mixtures of these sugars (10 g·l−1) by Candiada wickerhamii in batch cultures under aerobic and non-aerated conditions was investigated. Glucose was utilized first followed by cellobiose after a diauxic lag. Ethanol was produced from glucose under both aerobic and non-aerated conditions. Following glucose depletion under aerobic conditions, ethanol (produced during growth on glucose) and cellobiose were utilized simultaneously. Under non-aerated conditions ethanol was produced from cellobiose after the diauxic lag. When the glucose concentration was increased from 2 to 8 g·l−1 in glucose: cellobiose mixtures (total sugar 10 g·l−1), decreases of 66–91% were observed in the specific rates of growth, ethanol production, β-glucosidase production and sugar utilization on cellobiose as well as an increase in the diauxic time lag under aerobic and non-aerated conditions. After depletion of glucose, the viability of C. wickerhamii decreased during cellobiose utilization.