The production of an extracellular β-glucosidase by Aspergillus niger NRRL 599 was optimized using submerged fermentation technique. Effect of different media, different carbon sources, initial pH of the fermentation medium, temperature, incubation period and inoculum size on the production of β-glucosidase enzyme was investigated. A. niger NRRL 599 produced maximum extracellular β-glucosidase (4.48 U/mg) in Eggins and Pugh medium with 1% wheat bran (w/v) at pH 5.5 inoculated with 4% conidial suspension after 96 h of incubation at 30°C. Purified β-glucosidase gave K m and V max values of 3.11 mM and 20.83 U/mg respectively for pNPG hydrolysis. The enzyme was optimally active at pH 4.8 and at temperature of 60°C. Thermodynamic parameters, E a , ∆H and ∆S were found to be 52.17 KJ/mol, 49.90 J/mol.K and -71.69 KJ/mol, respectively. The pKa 1 and pKa 2 of ionizable groups of active site residues involved in V max were calculated to be 4.1 and 6.0 respectively.

Pretreatment of the cellulosic substrate has miracle effect on the enhancement of cellulase production by fungal strains. A thermophilic strain of Humicola insolens TAS-13 was locally isolated and was tested for cellulases production under solid-state fermentation conditions using sugar cane bagasse as substrate. The cultural conditions for the H. insolens were also optimized for the higher rate of cellulase secretion. In order to enhance the production rate of heterogenous cellulosic proteins, bagasse was pretreated with NaOH, H 2 SO 4 , H 2 O 2 and H 2 O 2 +1.5%NaOH. The pretreatment of bagasse with 2.0% H 2 O 2 along with 1.5% NaOH enhanced the biosynthesis of cellulases by H. insolens. Production rate was also optimized with different parameters like thickness of fermentation medium, initial pH, incubation time and temperature. The thickness of the fermentation medium of 0.8 cm (10 g) with pH range of 5.5 was found to be better for enhanced production at 50°C. The yield of the enzyme was reached maximum with CMC-ase (18.98 U/g/min), FP-ase (13.63 U/g/min), -glucosidase (19.54 U/g/min) 72 h after inoculation.

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