(626b) Comparison of Bioethanol Production with Saccharomyces Cerevisiae Immobilized On Different Supports

Use of immobilized yeast in bioethanol fermentation generally increases ethanol yield and productivity compared to free cell fermentation. In present work, different supports (wheat straw, pine wood chips, granular activated carbon, and cotton balls) were compared for their immobilization ability for yeast Saccharomyces cerevisiae. The immobilization supports were characterized for their surface properties like BET surface area, pore volume and average pore size. The immobilization was carried out by culturing 48 h grown S. cerevisiae culture with immobilization support for 24 h with gentle shaking. The immobilization was confirmed by optical microscope and by the efficiency of immobilized cells to ferment glucose faster compared to free culture.

Fermentation experiments with glucose as sole substrate (initial concentration 155.0±5.0 g/l) were carried out using immobilized yeast and free cells. Pine wood chips (PWC) and cotton balls (CB) proved to be better supports for immobilization and bioethanol production as evident by their higher volumetric ethanol productivity (Q_p) of 1.5 g/L.h and 1.44 g/L.h respectively while with wheat straw, higher Q_p (1.4 g/L.h) was observed but desorption of cells from support into medium was also high. Granular activated carbon (GAC) proved to be least efficient as a yeast support with lowest Q_p (0.684 g/L.h) and sugar utilization (68%). Except GAC, immobilized cells produced ethanol 1.4-1.6 times faster compared to free cells. PWC seemed to be better and efficient support for yeast immobilization.