Characterisation of biomass degrading xylanolytic enzymes of Penicillium chrysogenum produced using sugarcane bagasse

Penicillium chrysogenum CCDCA10746 secretome (SPc) produced using raw sugarcane bagasse was used to hydrolyse the hydrothermally pretreated sugarcane bagasse, in order to solubilise xylan to produce xylose with the conversion rate of 67%. The secretome was active in a wide pH range and exhibits increased thermostability (t(1/2) 8 h) than purified PcX2, a 23 kDa endo-8-1,4-xylanase of GH11 family, identified by mass spectrometry and zymogram. Xylanolytic activity was sensitive to Cu+2 and Zn+2 ions. In trials where enzymes were exposed to lignin-derived phenolic compounds: vanillin, cinnamic acid, and 4-hydroxy-benzoic acid inhibited the 70% activity of xylanase. On contrary, both enzymes showed resistance for tannic acid, additionally PcX2 was resistant to p-coumaric and SPc to gallic acid. PcX2 showed a binding affinity of KM 0.53 mg/mL and Vmax 0.21 U/mg for oat spelt xylan. Ionization of histidine appeared to be a crucial event in substrate binding and catalysis of PcX2 since decrease in fluorescence intensity and optimum activity was observed at pH 6.0.