Journal of Bioscience and Bioengineering, Vol.105, No.2, 90-96, 2008
Strategies for reducing supplemental medium cost in bioethanol production from waste house wood hydrolysate by ethanologenic Escherichia coli: Inoculum size increase and Coculture with Saccharomyces cerevisiae
In this paper, we report a simultaneous realization of both efficient ethanol production and saving medium nutrient (corn steep liquor ICSL]) during bioethanol fermentation of overliming-treated hydrolysate of waste house wood (WHW) using ethanologenic Escherichia coli K011. In cultivation using WHW hydrolysate supplemented with 4% (v/v) CSL and 0.2 g-dry cell weight (DCW)/l E. coli K011 cells, the overall ethanol yield reached 84% of the theoretical value at 61 h. When we conducted the cultivation with 1% CSL to reduce the supplemental medium cost, the overall ethanol yield remained in the range of 66-72% even at 90 h. We proposed two alternative methods for increasing the overall yield even with 1% CSL. The first method involved increasing the inoculum size of E. coli K011 up to 0.8 g-DCW/l, where 83% of the overall yield was attained at 60 h of cultivation. The second method involved the coculture of 0.2 g-DCW/l E. coli K011 together with 0.02 g-DCW/l of Saccharomyces cerevisiae TJ1, and the overall yield reached 81% at 47 h of cultivation.
Keywords:bioethanol;waste house wood;Escherichia coli;corn steep liquor;coculture;Saccharomyces cerevisiae