A moderately thermotolerant bacterial strain was isolated from the hot spring of Tatta Pani (AJ and K) Pakistan and was designated as Bacillus subtilis strain GQ 301542 after biochemical, morphological and 16S rDNA sequence analysis. This strain and its catabolite repression resistant mutant CRM197 were utilized for the study of different production kinetic parameters of both endoglucanase and cellobiohydrolase. Time course study on one monomeric (glucose), one dimeric (maltose) and two polymeric substrates (α-cellulose and wheat straw) was carried out at different time intervals (4 - 28 h, after each 4 h) for determining the maximum enzyme productivity on a particular substrate. Maximum rate of englucanase production by the mutant (53.1 IU/L/h) was significantly (P = 0.0007) higher than that (23.7 IU/L/h of the parental organism following their growth on glucose in Dubos salts medium while the optimum product yields (Yp/s) was calculated as 69.0 IU/g S (parent) and 82.3 IU/g S (mutant) for cellobiohydrolase production. Deoxy-D-glucose resistant mutant was significantly (p = 0.03 to 0.0007) improved over its parental strain with respect to some substrate consumption and all product formation parameters and can easily degrade cellulosic biomass for production of fermentable carbohydrates.
Key words: Cellobiohydrolase, endoglucanase, thermotolerant, Bacillus subtilis.
Abbreviations: µ, Specific growth rate (h-1); Qs, rate of subs/h); Yp/s, product yield (IU/g S utilized); Yp/x, specific yield of enzyme produstrate (S) consumption (g S/L/h); Qx, rate of cell mass formation (g cells/L/h); qs, specific rate of substrate consumption (g S/g cells/h); Yx/s, g (cells)/ g (S) consumed; Qp, rate of product formation (IU/L/h); qp, specific rate of enzyme production (IU/g cellction (IU/g cells); CBH, cellobiohydrolase; CMC, carboxymethyl cellulose; CMCase, carboxymethyl cellulose.
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