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Zhang J.,Shandong University | Zhang J.,Shandong Academy of Sciences | Wang M.,Shandong University | Gao M.,Japan National Institute of Advanced Industrial Science and Technology | And 6 more authors.
Bioenergy Research | Year: 2013

Acetone-butanol-ethanol (ABE) production from corncob was achieved using an integrated process combining wet disk milling (WDM) pretreatment with enzymatic hydrolysis and fermentation by Clostridium acetobutylicum SE-1. Sugar yields of 71. 3 % for glucose and 39. 1 % for xylose from pretreated corncob were observed after enzymatic hydrolysis. The relationship between sugar yields and particle size of the pretreated corncob was investigated, suggesting a smaller particle size benefits enzymatic hydrolysis with the WDM pretreatment approach. Analysis of the correlation between parameters representing particle size and efficiency of enzymatic hydrolysis predicted that frequency 90 % is the best parameter representing particle size for the indication of the readiness of the material for enzymatic hydrolysis. ABE production from corncob was carried out with both separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes using C. acetobutylicum SE-1. Interestingly, when considering the time for fermentation as the time for ABE production, a comparable rate of sugar consumption and ABE production in the SHF process (0. 55 g/l·h sugar consumption and 0. 20 g/l·h ABE production) could be observed when glucose (0. 50 g/l·h sugar consumption and 0. 17 g/l·h ABE production) or a mixture of glucose and xylose (0. 68 g/l·h sugar consumption and 0. 22 g/l·h ABE production) mimicking the corncob hydrolysate was used as the substrate for fermentation. This result suggested that the WDM is a suitable pretreatment method for ABE production from corncob owing to the mild conditions. A higher ABE production rate could be observed with the SSF process (0. 15 g/l·h) comparing with SHF process (0. 12 g/l·h) when combining the time for saccharification and fermentation and consider it as the time for ABE production. This is possibly a result of low sustained sugar level during fermentation. These investigations lead to the suggestion that this new WDM pretreatment method has the potentials to be exploited for efficient ABE production from corncob. © 2012 Springer Science+Business Media, LLC. Source


Zhou G.,Dalian Polytechnic University | Lu J.,Dalian Polytechnic University | Li Z.,Shandong University | Li J.,Dalian Polytechnic University | And 11 more authors.
Shengwu Gongcheng Xuebao/Chinese Journal of Biotechnology | Year: 2012

Penicillium decumbens T. is an important filamentous fungus for the production of cellulases to effectively degrade lignocellulose for second generation biofuel production. In order to enhance the capability of Penicillium decumbens to produce cellulases, we constructed a creB (a deubiquitinating enzyme encoding gene) deletion cassette, and generated a creB knockout strain with homologous double crossover recombination. This mutation resulted in a detectable decrease of carbon catabolite repression (CCR) effect. The filter paper activity, endoglucanase activity, xylanase activity and exoglucanase activity of the ΔcreB strain increased by 1.8, 1.71, 2.06 and 2.04 fold, respectively, when comparing with the parent strain Ku-39. A 2.68 fold increase of extracellular protein concentration was also observed. These results suggest that the deletion of creB results in CCR derepression. These data also suggest that CREB influences cellulase production of Penicillium decumbens. In generation, this study provides information that can be helpful for constructing cellulase hyper-producing strain. © 2012 Chin J Biotech. All Reserved. Source

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