Ethanol production from wheat straw by Saccharomyces cerevisiae and Scheffersomyces stipitis co-culture in batch and continuous system

• In batch and continuous processes, co-culture produced higher amount of ethanol.
• In batch system, SVSF process resulted in a decrease in process duration.
• In ICR, 235.43 g/L day ethanol was produced from wheat straw hydrolysate.
• S. stipitis was more sensitive to mass transfer limitations and O2 concentration.

In this research, Scheffersomyces stipitis and Saccharomyces cerevisiae in immobilized and suspended state were used to convert pentose and hexose sugars to ethanol. In batch and continuous systems, S. stipitis and S. cerevisiae co-culture performance was better than S. cerevisiae. Continuous ethanol production was performed in packed bed immobilized cell reactor (ICR). In ICR, S. stipitis cells were found to be more sensitive to oxygen concentration and other possible mass transfer limitations as compared to S. cerevisiae. Use of co-immobilized S. stipitis and S. cerevisiae resulted in maximum xylose consumption (73.92%) and 41.68 g/L day ethanol was produced at HRT (hydraulic retention time) of 6 h with wheat straw hydrolysate. At HRT of 0.75 h, the highest amount of ethanol with the values of 356.21 and 235.43 g/L day was produced when synthetic medium and wheat straw hydrolysate were used as feeding medium in ICR, respectively.