Directed Evolution of Xylanase from Dickeya dadantii DCE-01 with Improved Enzymatic Activity

Xylanase, an essential enzyme for breaking down xylan, faces limitations in its industrial applications due to the relatively low catalytic activity of the wild type. Directed evolution was used to enhance the catalytic efficiency of xylanase that originated from the Dickeya dadantii DCE-01. A xylanase variant (Xyn-ep) was obtained with improved catalytic activity by random mutant library employing two rounds of error-prone PCR. The results showed that the Xyn-ep demonstrated enzyme activity 1.6 times higher than that of wild-type xylanase. Sequencing analysis pinpointed key mutation sites at S159P, K212N, and N397S, respectively. Homology modeling was used to analyze the location of the mutation sites and to investigate the mechanism of the improved catalytic performance. The mutant Xyn-ep showed improved catalytic performance by error-prone PCR. Additionally, the increased flexibility of the loop of the mutant may contribute to the enhanced activity. These findings indicate that error-prone PCR is an effective method for enhancing enzyme activity and that the mutant Xyn-ep may be a new GH30 xylanase, being a potential candidate for industrial applications such as bast fiber bio-degumming, cotton bio-refinery, paper making, and so on.