Improved Production Of Microbial Transglutaminase From Streptomyces Hygroscopicus By Fermentation Strategies And Mutation

Microbial transglutaminase (MTG; protein-glutamineγ-glutamyltransferase, EC 2.3.2.13) is a recently developed enzyme and is capable of catalyzing acyl transfer reactions, which introduces covalent cross-links between proteins, peptides and various primary amines. So it has potential application in food processing, cosmetic, pharmacy and other industries.This study is mainly aimed at enhancing the production of microbial transglutaminase (MTG) by Streptomyces hygroscopicus. The relatively high cell density culture was invesgated. The effect of DO concentration and the effect of mutagenesis of Streptomyces hygroscopicus were researched, respectively. The following researches have been done:1. The relatively high cell density culture of Streptomyces hygroscopicus was investigated, the optimized initial concentration of glucose was 10 g/L.The effects of exponential feeding of glucose and the addition of nitrogen source on MTG production were investigated. The results showed that keeping a high specific growth rate (0.15 h-1) in 8-16 h and a relative low specific growth rate (0.10 h-1) during later time could obtain high-cell density.2. Effect of nitrogen sources addition on MTG fermentation by Streptomyces hygroscopicus was investigated. Nitrogen sources were added until the end of cells growing. The results showed that MTG activity reached 5.79 U/mL by adding 50 g/L soybean.3. The effect of dissolved oxygen (DO) concentration on the batch production of MTG in a 3 L stirred fermentor by Streptomyces hygroscopicus was studied. It was found that keep the DO at 30% during 0-20 h, and 10% during later time, the air flow rate was controlled at 1.25 vvm all the time in the fermentation process, the final MTG activity reached 5.88 U/mL achieving the unification of high MTG yield and high productivity.4. Streptomyces hygroscopicu CCTCC M203062 was mutagenized by UV and N~+-Implantation, and screened by 2-deoxy-D-glucose. DG-1, which is resistant to catabolite repression, was screened. The highest activity reached 8.19 U/mL, increased by 96% over the parent strain.