Production of Cellulases by Aspergillus sp. GDX02 in a Solid-State Fermentation Using Oil Palm Empty Fruit Bunch
A reduction in enzyme cost is one of the important factors for making bioethanol production more economically feasible. To this aim, we isolated a fungus, GDX02, to produce cellulases using agricultural wastes, including empty fruit bunch (EFB), under sol
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Abstract A reduction in enzyme cost is one of the important factors for making bioethanol production more economically feasible. To this aim, we isolated a fungus, GDX02, to produce cellulases using agricultural wastes, including empty fruit bunch (EFB), under solid-state fermentation (SSF). This study was conducted to determine the best substrate and optimal fermentation conditions for maximum cellulase production using GDX02. Of the different substrates tested, rice straw resulted in the highest enzyme production. As a nitrogen source, a supplement of yeast extract was necessary to achieve high enzyme activity. In particular, FPase activity reached its maximum at a supplement of 7 % yeast extract, whereas bglucosidase activity experienced little change under all concentrations of yeast extract tested. The GDX02 produced high FPase and b-glucosidase after three-day culture of EFB at 40 % moisture level. The saccharification yield of pretreated EFB by GDX02 cellulase was comparable to that from the commercial enzymes Celluclast and C-Tec2, indicating the great potential use of GDX02 cellulase for cellulosic ethanol production from EFB. Keywords Cellulase Aspergillus
Oil palm empty fruit bunch Solid-state fermentation
H. W. Kim G. J. Lee D. M. Kim Y. W. Lee Y. S. Kim (&) H-J.Chung (&) GenDocs Inc, Daejeon, Republic of Korea e-mail: [email protected] H-J.Chung e-mail: [email protected]
R. Pogaku et al. (eds.), Developments in Sustainable Chemical and Bioprocess Technology, DOI: 10.1007/978-1-4614-6208-8_7, Springer Science+Business Media New York 2013
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Introduction Lignocellulose, an important source for the production of both renewable energy and chemicals, is composed of cellulose and hemicellulose that can be hydrolyzed into glucose or xylose by cellulases and hemicellulases, respectively. Cellulases are a mixture of endo-D-glucanase, exo-D-glucanase, and b-glucosidase that synergistically convert cellulose into glucose. The cellulases are mostly produced by fermentation of the fungi Trichoderma and Aspergillus under a condition of either submerged or solid media. Solid-state fermentation (SSF) is a process wherein the solid substrate provides both the nutrients and physical support during the culture. SSF has been widely employed in the production of industrial enzymes due to its several advantages over submerged fermentation, including higher concentration of enzymes, high volumetric productivity, lower operating expenses, and lower sterility demand. Besides, SSF generates less wastewater because of lower water requirements. Agro-industrial by-products and crop residues can be used as carbon sources for cellulase production in SSF at a lower cost. Oil palm empty fruit bunch (EFB) is an agricultural by-product rich in cellulose and hemicellulose, typically containing 35 to 40 % cellulose and 20 to 25 % hemicellulose. It is abundantly produced in Indonesia and Malaysia. Palm oil mills in Malaysia generate 2.4 million tons of EFB annually. EFB was often used as f
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