Isolation and utilization of cellulolytic microorganisms for cellulase production through solid state fermentation of corncobs

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Date
2011
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This research was conducted to investigate production of cellulase enzymes from a cellulolytic soil microorganism cultured on corncobs under solid state conditions. The cellulolytic fungi isolated from soil samples were Aspergillus niger, Neurospora crassa, Penicillium sp., Rhizopus sp., Trichoderma sp. The bacteria isolated from the same soil samples were Streptomyces sp., Clostridium sp and Klebsiella pneumonia. Out of these microorganisms, A. niger had the highest clearing zone to mycelium diameter ratio of 0.26 when cultured on carboxymethylcellulose agar and so was selected for the solid state fermentation experiments. The fermentation was carried out under different temperatures (27, 37, 47 and 57 °C) and initial spore concentrations of the fungi (1.3x106, 2.3x106 and 4.5x106) in order to investigate how these parameters affect the production of cellulase enzymes. Undiluted spore inoculum (containing about 4.5x106 spores) gave the best fermentation results in terms of the amounts of glucose released (1.38 mg ml-1) from the substrate and the concentration of enzymes produced by the fungi throughout the 15-day period. Although 47 °C was best for the lag phase of A. niger growth on corncobs, 37 °C is most suitable for exponential growth and enzyme production under solid state conditions. At 37 °C, enzyme activities of the fermentation filtrates were 0.35, 0.44 and 0.45 CMC units respectively for 5, 10 and 15 days of fermentation. These values were the highest obtained as compared with values obtained when the other temperatures were used. Thus the strain of A. niger used can be described as a highly cellulolytic mesophile.
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A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Master of Science in Biotechnology,
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