Abstract
The thermal stability of Trichoderma reesei Xyn III was improved by directed evolution. The random mutations were introduced into xyn III gene using error prone PCR and random mutagenesis library was constructed into E. coli cells. The mutated Xyn III that had higher thermal stability was screened. The selected mutant had two amino acids substitutions. Next, the saturation mutagenesis was introduced into this two amino acid positions. The most effective mutations were Gln to Ala and Asn to Tyr. This Xyn III mutant showed high thermal stability at 50℃ for 48 h.
