(40d) Efficient Fermentation of Glucose and Xylose Mixtures Using Immobilized Saccharomyces Cerevisiae on Pine Wood Chips and Free Pichia Stipitis

In this work, the ability of pine wood chips (PWC) as yeast support has been evaluated. Saccharomyces cerevisiae was immobilized on this biological support and mixed sugar fermentation was carried out with free culture of Pichia stipitis and immobilized S. cerevisiae. Pine wood was used in two forms; untreated (UPW) and treated (TPW). Fermentation experiments with free culture of both the yeasts were also carried out. The immobilization was carried out by co-culturing 48 h grown S. cerevisiae culture with PWC for 24 h with gentle shaking. The immobilization was confirmed by optical microscope and by the efficiency to ferment glucose quickly as compared to free culture. Initial experiments were carried out with 50 g/l mixture of glucose and xylose (1.5:1.0 ratio of glucose to xylose).

The efficiency of support for fermentation was evident by the fact that 63-70% of sugars were consumed in only 12 h and 84-93% fermentation efficiency was observed with almost complete utilization of both the sugars in 44 h. Doubling the sugar concentration (100 g/l) had little effects on fermentation efficiency but time required for complete sugar fermentation was increased to 78 h from 44 h. TPW worked out as a better support than UPW as the surface area of the former increased after the treatment to 1.5 times.