Simultaneous Saccharification and Fermentation of Corn Straw to Lactic Acid

Q. Wang, D. Zou, H. Ma, X. Wang and Y. Ji

Abstract
The utilization of corn straw to produce lactic acid could largely save the resource as well as decrease the amount of agricultural waste. In this study, orthogonal experimental design was adopted to investigate the optimum conditions for cellulase production from corn straw, and then the cellulase was further used to produce lactic acid through simultaneous saccharification and fermentation (SSF) process. (NH4)2SO4 and Tween 80 were also used to test their effects on lactic acid production. The optimum conditions were determined as follows: solid-to-liquid ratio was ζ = 1 : 3, pH of the substrate mixture was 4.5, inoculum size of Trichoderma koningii was G = 12 % (v/m), fermentation time was t = 84 h. Corresponding maximum cellulase of H = 2630.3 U g–1 straw was achieved. With the produced cellulase added, the maximum lactic acid concentration of γ = 20.2 g L–1 could be achieved inoculated with lactic acid bacteria T50 at ϑ = 45 °C. As compared with control (non-addition), addition of w = 2 % (NH4)2SO4 could increase the lactic acid by 3.6 %, while addition of Tween 80 could shorten the fermentation time from t = 108 h to t = 72 h. The result indicated that utilization of corn straw as substrate to produce cellulase and lactic acid was applicable and could reduce pollution, thus this was worth investigating further.

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Keywords
cellulose, simultaneous saccharification and fermentation (SSF), lactic acid, corn straw, Trichoderma koningii