Effect of different biological surfactants on engineering Saccharomyces cerevisiae in simultaneous saccharification and fermentation of corncob

Abstract

Lignocellulose is considered to be a good resource for producing renewable energy. This paper reports on the effect of three surfactants [polyoxyethylene (80) sorbitan monooleate (POE80), rhamnolipid, and tea saponin] on cellulase (CBH/EG/BG) expression of Saccharomyces cerevisiae in simultaneous saccharification and fermentation (SSF) of corncob. In this work, the optimal surfactant concentrations for yeast growth were 0.1% POE80, 0.05% rhamnolipid, and 0.002% tea saponin. In the process of SSF, the reducing sugar content with 0.1% POE80 was 13.5% higher than the control at 24 h. The reducing sugar content with 0.05% rhamnolipid was higher than the control at 120 h, and reached the maximum difference of 18.2% in 120 h. The addition of 0.002% tea saponin exhibited the lowest promotion effect on the reducing sugar content in SSF compared with POE80 and rhamnolipid. However it reached the maximum difference of 8% in 120 h. Compared with the control, 0.1% POE80, 0.05% rhamnolipid, and 0.002% tea saponin presented different degrees of increase in reducing sugar content and viable count in the SSF. The results showed that the addition of the surfactants in SSF increased the growth rate of strains and promoted the saccharification efficiency of the substrate. This study lays a foundation for the application of surfactants in bio-energy research.