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

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 fermentatio

Isolation, Purification, and Characterization of Xylanase Produced by a New Species of Bacillus

A thermoalkalophilic new species of Bacillus, similar to Bacillus arseniciselenatis DSM 15340, produced extracellular xylanase under solid state fermentation when wheat bran is used as carbon source. The extracellular xylanase was isolated by ammonium sulfate (80%) precipitation and purified using ion exchange chromatography. The molecular weight of xylanase was ~29.8 ;kDa. The optimum temperature and pH for the enzyme activity were 50°C and pH 8.0. The enzyme was active on birchwood xylan and little active on p-nitrophenyl xylopyranoside but not on Avicel, CMC, cellobiose, and starch, showing its absolute substrate specificity. For birchwood xylan, the enzyme gave a Km 5.26 ;mg/mL and Vmax 277.7 ;μmol/min/mg, respectively. In addition, the xylanase was also capable of producing high-quality xylo-oligosaccharides, which indicated its application potential not only in pulp biobleaching processes but also in the nutraceutical industry