Sunday, May 4, 2008
3-30

Identification of phenolic compounds in lignocellulosic hydrolysates and its detoxification by enzyme for the production of butanol by Clostridia

Dae Haeng Cho1, Yun Jie Lee2, Byoung In Sang2, and Yong Hwan Kim1. (1) Dept. of Chemical engineering, Kwangwoon University, 447-1, Wolgye-Dong, Nowon-Gu, Seoul 139-701, South Korea, (2) Hazardous substance research center, Korea Institute of Science and Technology, 131, Cheongryang, Seoul 130-650, South Korea

With inevitable depletion of fossil fuel and increase of problem of greenhouse effect, the needs of alternative and non-petroleum-based sources of energy being on the rise. Increased attention has been focused on alcoholic liquid fuels, such as ethanol and butanol, prepared from lignocellulosics as an alternative to fossil fuels due to its net reduction of carbon dioxide emission. Lignocellulosic materials provide abundant and renewable resources and have great potential as a substrate for fermentation. Lignocellulosics contain cellulose and hemicellulose which can liberate sugars by steam and dilute acid hydrolysis. Lignocellulosic hydrolysates, however, contain not only fermentable sugars but also some compounds that inhibit microbial fermentation to desirable products, such as furan, weak acids, and various phenolic compounds [1]. Therefore, detoxification of hydrolysates, i.e., removal of inhibitory compounds is necessary before the fermentation for achieving high yield of products.

Phenols are oxidized by peroxidase to generate phenoxy radicals, which couple with other substrate molecules to form dimeric, oligomeric, and polymeric compounds. This enzymatic polymerization method can be exploited for the treatment of wastewater polluted with phenolic compounds. In the present study, we identified phenolic compounds and investigated the enzymatic detoxification of phenolic compounds found in lignocellulosic hydrolysates. The enzyme reaction was optimized as a function of external variables, such as pH, enzyme dose, and hydrogen peroxide to substrate ratio. The detoxified materials were used as substrate for butanol production from Clostridium beijerinckii in order to evaluate the toxicity of reaction product.


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