Monday, May 5, 2008
8-18

Optimization of lignin-degrading enzyme production of white-rot fungi, Phanerochaete chrisosporium and Dichomitus squalens, for the biological pretreatment of lignocellulose

Jin Seop Bak, Division of Food Bioscience and Technology, Korea University, College of Life Sciences and Biotechnology, Anam-dong, Seongbuk-gu, Seoul, South Korea, Yong-Su Jin, School of Biotechnology and Bioengineering, Sungkyunkwan University, Suwon, South Korea, and Kyoung Heon Kim, School of Life Science & Biotechnology, Korea University, College of Life Sciences and Biotechnology, Anam-dong, Seongbuk-gu, Seoul, South Korea.

Unlike various thermal or chemical processes for pretreating biomass, which are usually carried out at an extreme condition, the biological pretreatment using white rot basidiomycetous fungi could bring potential improvement in the current pretreatment and deconstruction of biomass by minimizing inhibitors and energy consumptions.  In our study, a lignin-degrading enzyme was selected as targets for the primary tool for disabling the natural recalcitrance of lingnocellulsic biomass.  The production of a fungal lignin-degrading enzyme, manganese peroxidase (MnP) by Phanerochaete chrisosporium and Dichomitus squalens was optimized.  Various culture conditions such as carbon, nitrogen, trace minerals, and vitamin sources were optimized against the activity of MnP in both cell-envelop-bound and intact-cell-bound forms by the response surface methodology (RSM) including the Plackett-Burman design (PBD), Box-Behnken design (BBD), and Ridge Analysis (RA).  For the direct measurement of change in the enzyme digestibility by using cellulose hydrolysis enzymes (Trichoderma reesei cellulase and Aspersillus niger beta-glucosidase) of biomass in the fungal culture media, the rice straw samples were periodically taken from the culture media, and the enzyme digestibility of the cellulose in the rice straw was measured.  The increase of enzyme digestibility exhibited a strong dependency on the activity of MnP in the cultivation medium of the fungi.  The result indicates that fungal fermentation of lignocellulose could be a potent alternative to the conventional thermochemical or chemical pretreatment processes.


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