Prediction of optimum reaction conditions for the thermo-tolerant acetylxylan esterase from Neocallimastix patriciarum using the response surface methodology

摘要

BACKGROUND: Xylan is the second most abundant renewable polysaccharide in nature and also represents an important industrial substrate. The complete degradation of xylan requires the combination of several types of xylanolytic enzymes, including endo-β-1,4-xylanases, β-xylosidases, and acetylxylan esterases. As a biocatalyst, xylanolytic enzymes with good thermal stability are of great interest, therefore, a thermo-tolerant acetylxylan esterase, AxeS20E, was investigated. RESULTS: The cDNAencoding the carbohydrate esterase (CE) domain of AxeS20E from Neocallimastixpatriciarum was expressed in Escherichia coli as a recombinant His6 fusion protein. The recombinant AxeS20E protein was obtained after purification by immobilized metal ion-affinity chromatography. Response surface modeling (RSM) combined with central composite design (CCD) and regression analysis were then employed for the planned statistical optimization of the acetylxylan esterase activities of AxeS20E. The optimal conditions for the highest activity of AxeS20E were observed at 54.6 C and pH 7.8. Furthermore, AxeS20E retained more than 85% of its initial activity after 120 min of heating at 80 C. CONCLUSIONS: The results suggested that RSM combined with CCD and regression analysis were effective in determining optimized temperature and pH conditions for the enzyme activity of AxeS20E. The results also proved AxeS20E was thermotolerant andmight be a good candidate for various biotechnological applications.