Screening and characteristics of a butanol-tolerant strain and butanol production from enzymatic hydrolysate of NaOH-pretreated corn stover

Abstract

As a gasoline substitute, butanol has advantages over traditional fuel ethanol in terms of energy density and hydroscopicity. However, solvent production appeared limited by butanol toxicity. The strain of Clostridium acetobutylicum was subjected to mutation by mutagen of N-methyl-N′-nitro-N-nitrosoguanidine for 0.5 h. Screening of mutants was done according to the individual resistance to butanol. A selected butanol-resistant mutant, strain 206, produced 50 % higher solvent concentrations than the wild-type strain when 60 g glucose/l was employed as substrate. The strain was also able to produce solvents of 23.47 g/l in 80 g/l glucose P2 medium after 70 h fermentation, including 5.41 g acetone/l, 15.05 g butanol/l and 3.02 g ethanol/l, resulting in an ABE yield and productivity of 0.32 g/g and 0.34 g/(l h). Subsequently, Acetone-butanol-ethanol (ABE) production from enzymatic hydrolysate of NaOH-pretreated corn stover was investigated in this study. An ABE yield of 0.41 and a productivity of 0.21 g/(l h) was obtained, compared to the yield of 0.33 and the productivity of 0.20 g/(l h) in the control medium containing 52.47 mixed sugars. However, it is important to note that although strain 206 was able to utilize all the glucose rapidly in the hydrolysate, only 32.9 % xylose in the hydrolysate was used after fermentation stopped compared to 91.4 % xylose in the control medium. Strain 206 was shown to be a robust strain for ABE production from lignocellulosic materials and has a great potential for industrial application.