Functional characterisation of a recombinant xylanase from Pichia pastoris and effect of the enzyme on nutrient digestibility in weaned pigs

摘要

The xyn2 gene of a filamentous mesophilic fungus, Trichoderma reesei, coding xylanase 2 (Xyn2) was previously expressed in Pichia pastoris. In the present study, the recombinant Xyn2 was prepared from a 15 litre fermenter, and subsequently characterised. It has been confirmed to have a molecular mass of 21kDa, an optimal pH of 6.0 and an optimal temperature of 60 degree C. When tested using oat-spelt xylan, it showed a Km and catalytic rate constant (kcat) of 1.1mg/ml and 512.4/s, respectively. Analysis of the products from oat-spelt xylan degradation confirmed that the enzyme was an endoxylanase with xylotriose and xylobiose as the main degradation products. The unprocessed Xyn2 was supplemented to a xylan-containing diet to determine its influences on performance and nutrient digestibilities by weaned pigs. Results showed that the average body-weight gain increased 16.9% when piglets received Xyn2 at a concentration of 500U/kg diet. There also was a positive (0.05