Protease Control In The Preparation Of Microbial Transglutaminase By Streptomyces Hygroscopicus

Microbial transglutaminase (MTG; protein-glutamineγ-glutamyltransferase, EC 2.3.2.13) 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, cosmetic, pharmacy, textile and other industries.Aimed to control the secretion of protease in the production of MTG by Streptomyces hygroscopicus WSH03-13, we observed the controlling strategy at the fementation, extraction and preparation process of MTG. The main research results were shown as follows:1. Optimized the conditions of zinc sulfate addition in the fermentation liquid. It confirmed the appropriate adding amount and adding time; We optimize the fermentation condition and get the optimal pH and preferable inoculation amount.2. After MTG fermentation condition was determined, fermentation was performed in 7L fermentor. When agitator speed was 400 rpm and aeration rate was 1.25 vvm, MTG activity reached 5.6 U/mL. It was showed that the level of protease activity could be controlled in the following extraction process.3. Ultrafiltration was used to concentrate the Microbial Transglutaminase (MTG) from fermentation liquid. Several factors, which influence the MTG activity and its recovery rate, were investigated to explore the optimal operation conditions during the ultrafiltration process. The results showed that polyethersulphone (PES) membrane with a molecular weight cut off (MWCO) of 30 kDa, the initial pH value of fermentation liquid at 7 and fermentation liquid was concentrated four times, the MTG yield rate could reach the best effect and the protease in the liquid was also low. Finally, after the ultrafiltration membrane was washed by NaOH solution(pH 11)for 50 min, its membrane flux could be recovered 98.12%.4. The methods of inhibiting protease in the production of microbial transglutaminase were investigated. The results showed that sodium hexametaphosphate (SHMP) was the most effective inhibitor to protease and the least concentration of SHMP was determined.5. The addition of SHMP before spray-drying procedure, could inhibit the...