Screening Of Xylanase High-producing Mutants Of Saccharomonospora Viridis By Atmospheric And Room Temperature Plasmas And Its Enzyme Characterization

Microbial xylanases have attracted considerable research interest in recent years because of their potential application in different areas of industrial production. Alkaline xylanase can reduce the amount of chlorine containing compound in pulp bleaching technology, and is beneficial to meet the demands of the increasingly strict standards of environmental requirements. Pulp bleaching with microbial xylanases is the development tendency of paper industry in the future.In order to obtain an industrial strain with higher xylanase production, the original strain of Saccharomonospora viridis was mutated by atmospheric and room temperature plasmas. The methods used to screen the mutant strain with higher xylanase production included transparent loop diameter measurement of selective medium with2%beech-wood xylan and shaking flask fermentation. The enzymatic properties of xylanase from different mutants were comparatively analysed by the method of DNS xylanase activity determination. In addition, the gene sequences and amino acid sequences of xylanase from six different mutants were studied in this paper. Main results were as follow.1. It has been demonstrated that both mutants AT22-2, AT24, AT28, AT29, CT22and BT76maintain good genetic stability. The enzyme activity in the fermentation liquor of six mutants at7d reached552.70U/mL,512.74U/mL,167.36U/mL,1,791.44U/mL,424.51U/mL and313.76U/mL, which were16.51,15.24,4.30,55.75,12.45and8.94times higher than that of the original strain, respectively.2. The enzymatic properties of xylanase from different mutants have a large amount of differences with each other and the original strain. In the results, the xylanases secreted by mutants AT22-2, AT24, AT29and CT22were with better thermostability and alkali-tolerance mong the six mutants. To predict, the xylanases from the four mutants above are potential candidates for future use in biotechnological applications particularly in the pulp and paper industry.3. The results of multiple sequence alignment of xylanase gene sequences and amino acid sequences showed that the xylanases gene sequences of mutants AT24, AT28, AT29and BT76had some certain changes. And those changes had led into the amino acid sequences altered. Furthermore, the xylanases gene sequence of mutant AT22-2and CT22were consistent with original stain. It’s estimated that those changes perhaps are the reasons of the varieties in xylanase activity and enzyme characterization.