Microwave-assisted pretreatment of corncobs for butanol production

Abstract

A two-stage pretreatment of corncobs using NaOH followed by H₂SO₄ combined with microwave radiation prior enzymatic hydrolysis has been examined. The optimum condition of second stage was obtained with response surface methodology (RSM) at a three-variable and five-level central composite design (CCD). A maximum concentration of glucose 48.58 g/l was obtained at the optimal condition of 2 % NaOH at 100ºC, 30 min, and SLR 67 for first stage and 1 % H₂SO4 at 156ºC, 16 min, and SLR 106 for second stage of two-stage pretreatment. The result showed that SLR and temperature are the most significant factors on the glucose concentration. After that, the hydrolysate was used to produce Acetone-Butanol-Ethanol (ABE) by Clostridium beijerinckii TISTRI146l. The overliming combined with diluted 4 times hydrolysate (D4O) technique gave the highest ABE yield of 0.41. It is suggested that the dilution and overliming process can reduce fermentation inhibitors, increase cell growth and improve ABE yield.