Production, Purification and Characterization of Xylanase from Oyster Mushroom (Pleurotus Sp.)

Abstract

Back gound: Xylanase is lignocellulolytic enzyme produced by Microorganisms, marine algae, protozoans, crustaceans, insects and snails. Fungal xylanases are attractive to be used in various industrial applications, but xylanase from oyster mushroom collected from Eucalyptus tree bark around Holetta is not screened and characterized. Therefore the objectives of this study were, to evaluate the in vitro production of xylanase by Pleurotus spp. using different lignocellulosic substrates, and to partially purify and characterize the xylanase produced by Pleurotus spp. with respect to changes in pH, temperature, and concentration of different substrates (wheat straw, teff straw, bean straw and Eucalyptus tree bark) to identify the most suitable medium for the production of xylanase. Results: The highest enzyme production was obtained on bean straw (2.38U/ml and 1.77 U/ml in solid state fermentation and submerged fermentation, respectively) and the lowest was obtained in media containing Eucalyptus tree bark (0.36 U/ml and 0.58 U/ml in solid state fermentation and submerged fermentation, respectively). Optimal production of xylanase was obtained when Pleurotus ostreatus was grown in solid state fermentation using wheat straw supplemented with 5% birch wood xylan, peptone and KCl salt at pH 4.0 and a temperature of 30^∘C under stationary conditions for four days. The xylanase from P. ostreatus was partially purified to homogeneity using different concentrations (30 to 80% (wt/vol) of ammonium sulphate. Xylanase having highest specific activity (11.47U/ml) and total protein content of 0.631mg/ml was recovered from the culture supernatant when precipitated with 40% (wt/vol) ammonium sulphate. The optimum activity was observed at 50^∘C and pH 6.0. The enzyme was very stable at a wide range of temperature and pH. Its apparent K_m and V_max were 186.67 µg/ml and 11.58µmole/min, respectively, showing its high affinity towards its substrate. Conclusions: Based on these results, the enzyme seems to be very stable at a wide range of temperature and pH in addition to having high affinity toward its substrate. These characteristics hopefully would make this enzyme potentially very attractive for animal feed processing and other industrial applications

Keywords: Pleurotus spp. Solid state fermentation, Xylanase, Wheat straw.