Background:
As the supply of starch grain and sugar cane, currently the main feedstocks for bioethanol production, become limited, lignocelluloses will be sought as alternative materials for bioethanol production. Production of cellulosic ethanol is still cost-inefficient due to the low final ethanol concentration and the addition of nutrients. Here, simultaneous saccharification and co-fermentation (SSCF) of lignocellulosic residues from commercial furfural production (furfural residue, FR) and corn kernels were carried out to compare different nutritional media. The final ethanol concentration, the yield, the amount of live yeast cells and yeast cell death ratio were investigated to evaluate the effectiveness of integrating cellulosic and starch ethanol.
Results:
Both the ethanol yield and amount of live yeast cells increased with increasing corn kernels concentration, while the yeast cell death ratio decreased in the SSCF of FR and corn kernels. An ethanol concentration of 73.1 g/L at 120 h, which corresponded to a 101.1% ethanol yield based on FR cellulose and corn starch, was obtained in the SSCF of 7.5% FR and 14.5% corn kernels with mineral salt medium. SSCF could simultaneously convert cellulose into ethanol from both corn kernels and FR, and the SSCF ethanol yield was similar between the organic and mineral salt media.
Conclusions:
Starch ethanol promotes cellulosic ethanol by providing important nutrients for fermentative organisms whereby cellulosic ethanol promotes starch ethanol by providing cellulosic enzymes that convert the cellulosic polysaccharides in starch materials into additional ethanol. It is feasible to produce ethanol in SSCF of FR and corn kernels with mineral salt medium. It would be cost-efficient to produce ethanol in SSCF of high water insoluble solid (WIS) of lignocellulosic materials and corn kernels. Compared with prehydrolysis and fed-batch strategy using lignocellulosic materials, addition of starch hydrolysates to cellulosic ethanol production is a more suitable method to improve the final ethanol concentration.