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Optimization of cellulase production using

Saravanan P, Muthuvelayudham R, Rajesh Kannan R, Viruthagiri T

《化学科学与工程前沿（英文）》 2012年第6卷第4期页码 443-452 doi: 10.1007/s11705-012-1225-1

摘要： The potential of for cellulase production using pineapple waste as substrate has been investigated. A maximum cellulase activity of 9.23 U/mL is obtained under the optimum experimental conditions: pH (5.5), temperature (37.5°C), initial substrate concentration (3%), inoculum concentration (6.6 × 10 ?CFU/mL), and culture time (6 days). Box-Behnken design (BBD) statistical tool and genetic algorithm (GA) are used to optimize the process parameters. The BBD study of linear and quadratic interactive effects of experimental variables on the desired response of cellulase activity showed that the second order polynomial is significant ( = 0.9414). The experimental cellulase activity under the optimal conditions identified by the BBD is 9.23 U/mL and that by GA is 6.98 U/mL. This result indicates that the BBD model gives better result than GA in the present case.

关键词： cellulase pineapple waste Trichoderma reesei Box-Behnken design genetic algorithm

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Advances in the study of directed evolution for cellulases

Hailong LIN, Weiguang LI, Changhong GUO, Sihang QU, Nanqi REN

《环境科学与工程前沿（英文）》 2011年第5卷第4期页码 519-525 doi: 10.1007/s11783-011-0326-2

摘要： If cellulose can be effectively hydrolyzed into glucose by cellulase, the production costs of hydrogen, ethanol or other chemicals from cellulosic materials will be greatly decreased, and economically viable production of biohydrogen and bioethanol will become feasible. Cellulose is degraded into glucoses by multi-component enzyme systems. Nowadays cellulases are widely used in brewing, food, bioenergy, fodder, textiles, paper, pharmaceuticals, environmental protection and other industries. However, existing cellulases have several problems that limit their wider applications, including the low turnover number for solid cellulosic materials, and low stability in adapting to various application conditions. For example, high temperature, low pH, and so on. Application of directed evolution technology may be one of the most effective ways for improving the characteristics of cellulases. This paper presents a brief review of the cellulose hydrolysis mechanism by cellulase, advances in cellulases (endoglucanase and -glucosidase) improvement by directed evolution for several characteristics (for instance, thermal stability, pH adaptability and enzyme activity), limitations of directed evolution for cellulases, and the outlook for directed evolution for cellulase.

关键词： biohydrogen bioethanol cellulase cellulose directed evolution

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Direct ethanol production from rice straw by coculture with two high-performing fungi

Maki TAKANO, Kazuhiro HOSHINO

《化学科学与工程前沿（英文）》 2012年第6卷第2期页码 139-145 doi: 10.1007/s11705-012-1281-6

摘要： To develop efficient and economical direct ethanol production from fine rice straw crashed mechanically, two high-performing fungi, which can secret hyperactive cellulases and/or ferment effectively various sugars, were selected from some strains belong to preserved in our laboratory. The simultaneous saccharification and fermentation (SSF) by coculture with these fungi was investigated. The screening of high-performing fungi resulted in the selection of NBRC 4572 as an ethanol-producing fungus and NBRC 5398 as a cellulase-secreting fungus. The strain 4572 produced ethanol aerobically from glucose and xylose in high yields of 0.420 g/g at 36 h and 0.478 g/g at 60 h, respectively, but secreted fairly low cellulases. On the other hand, the strain 5398 also produced ethanol from glucose in yield of 0.340 g/g though it had a little growth in xylose culture. However, it secreted hyperactive cellulases that are essential for hydrolysis of rice straw in culture and the maximum activities of endo-β-glucanase and β-glucosidase were 2.11 U/L and 1.47 U/L, respectively. In SSF of rice straw by coculture with two fungi selected, the ethanol production reached 1.28 g/L after 96 h when the inoculation ratio of the strain 5398 to the strain 4572 was 9.

关键词： Mucor circinelloides ethanol production cellulase secretion SSF coculture rice straw