A Study of the cellulases produced by three mesophilic actinomycetes grown on bagasse as substrate.
The cellulases that strains of Streptomyces albogriseolus, S. nitrosporeus, and Micromonospora melanosporea produce when grown on untreated ballmilled bagasse were investigated. Optimum conditions for extracellular cellulase production and activity were determined to be growth at pH 6.7-7.4 and 25-35 degrees C for 4-5 days and assay at pH 5.0-6.0 and 45-55 degrees C, respectively. The endoglucanases were thermally stable at 50 degrees C, but the Avicelases had a half-life of approximately 24 h at this temperature. Nearly half of the endoglucanases and almost all of the Avicelases were absorbed on ballmilled bagasse after 15 min incubation at 50 degrees C. The beta-glucosidases were found to be mainly intracellular or cell wall bound. These mesophilic actinomycetes concomitantly produced xylanases and beta-xylosidases with cellulases that, apart from cellobiose and glucose, also release xylose from bagasse. This feature may be advantageous in the commerical application of the enzymes of mesophilic actinomycetes for the saccharification of natural cellulosic substrates.
National Food Research Institute, Council for Scientific and Industrial Research, Pretoria 0001, South Africa.
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Van Zyl