• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.2
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• pp.99-105
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• 1991

This study was carried out to provide basic data to be necessary for the selection of an energy recovery process based on the characteristics of municipal solid wastes(MSW). The samples were collected at Kangdong-Ku in Seoul and conducted ultimate and proximate analyses. Laboratory scale anaerobic digesters were operated to determine the non biodegradable fractions of the wastes. The results indicated that carbon and hydrogen contents, and lower heating values could be calculated from the volatile contents of MSW by the following equations : C = 0.57 VS, H =0.084 VS, and HL=49.5 VS-(6-0.045VS) W. Nonbiodegradable fractions were respectively 58.9% of volatile matters and 77.7% of MSW. Incineration and refuse derived fuel(RDF) processes appeared to be the most efficient processes in terms of weight reduction and energy recovery, But determining the energy recovery processes, the fluctuations of heating values of MSW throughout a year and available landfill site and secondary pollution should be considered.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.6
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• pp.482-493
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• 2005

Biomass is originally photosynthesized from inorgainic compounds such as $CO_2$, minerals, water and solar energy. Recent studies have shown that anaerobic bacteria have the ability to convert recalcitrant biomass such as cellullosic or chitinoic materials to useful compounds. The biomass containing agricultural waste, unutilized wood and other garbage is expected to utilize as feed, food and fuel by microbial degradation and other metabolic functions. In this study we isolated several anaerobic, cellulolytic and chitinolytic bacteria from rumen fluid, compost and soil to study their related enzymes and genes. The anaerobic and cellulolytic bacteria, Clostridium thermocellum, Clostridium stercorarium, and Clostridium josui, were isolated from compost and the chitinolytic Clostridium paraputrificum from beach soil and Ruminococcus albus was isolated from cow rumen. After isolation, novel cellulase and xylanase genes from these anaerobes were cloned and expressed in Escherichia coli. The properties of the cloned enzymes showed that some of them were the components of the enzyme (cellulase) complex, i.e., cellulosome, which is known to form complexes by binding cohesin domains on the cellulase integrating protein (Cip: or core protein) and dockerin domains on the enzymes. Several dockerin and cohesin polypeptides were independently produced by E. coli and their binding properties were specified with BIAcore by measuring surface plasmon resonance. Three pairs of cohesin-dockerin with differing binding specificities were selected. Two of their genes encoding their respective cohesin polypeptides were combined to one gene and expressed in E. coli as a chimeric core protein, on which two dockerin-dehydrogenase chimeras, the dockerin-formaldehyde dehydrogenase and the dockerin-NADH dehydrogenase are planning to bind for catalyzing $CO_2$ reduction to formic acid by feeding NADH. This reaction may represent a novel strategy for the reduction of the green house gases. Enzymes from the anaerobes were also expressed in tobacco and rice plants. The activity of a xylanase from C. stercorarium was detected in leaves, stems, and rice grain under the control of CaMV35S promoter. The digestibility of transgenic rice leaves in goat rumen was slightly accelerated. C. paraputrificum was found to solubilize shrimp shells and chitin to generate hydrogen gas. Hydrogen productivity (1.7 mol $H_2/mol$ glucos) of the organism was improved up to 1.8 times by additional expression of the own hydrogenase gene in C. paraputrficum using a modified vector of Clostridiu, perfringens. The hydrygen producing microflora from soil, garbage and dried pelletted garbage, known as refuse derived fuel(RDF), were also found to be effective in converting biomass waste to hydrogen gas.