Isolation, identification and screening of potential cellulase-free xylanase producing fungi and its production

Abstract

In order to isolate cellulase-free xylanase producing fungi, screening and isolation was done using composting soil as microbial source. Eight fungal species were selected for further study based on clearing zones formation on agar media containing covalently linked xylan with dye cibacron brilliant red-3BA. Both solid state and submerged fermentations were done with eight fungal isolates to identify strain that could produce highest amount of cellulase-free xylanase at a pH of 5.5 and at 28 ± 2°C temperature. Under solid state conditions, 50% of the strains produced xylanase (45.78 to 923 U gds -1 ) and lower amount of cellulase (20 to 33 U gds -1 ). The amount of soluble protein was also determined which ranged between 67 to 99 mg gds -1 . In submerged conditions, 25% strains produced xylanase (45 to 205 U mL -1 ) and negligible amount of cellulase (12 to 13 U mL -1 ). The amount of soluble protein was determined which ranged between 45 and 85 U ml -1 in submerged conditions. Growth was determined in terms of mycelial dry weight which ranged between 0.70 and 2.90 mg mL -1 . Keywords: Cellulase-free xylanase, xylan, solid state fermentation, submerged fermentation