Screening And Optimization Of Fermenting Conditions Of A Nitrile Hydratase Producing Strain

Acrylamide is a widely used fine chemical industrial product which is mostly used to produce polyacrylamide and its ramifications. Polyacrylamide is used as water treatment chemicals, paper intensifier, sticking-preventor for drilling, fibre treatment and bond et al. In recent years, with broad application in the third oil extraction technology in our country, the demand of polyacrylamide is growing increasingly. Thus, as the monomer of polyacrylamide, the supply of acylamide falls short of demand and it will have a well market prospect.Compared with producing acrylamide in chemical method, the microbial method has many benefits such as high efficiency, high selectivity, mild reacting conditons, low cost and little environmental contamination. It becomes one of the researching hotspots at all times. Nitrile Hydratase as the catalyst of producing acrylamide by microbial method, can catalyze acrylonitrile to acrylamide. The key to producing acrylamide by microbial method is screening of the strain which can produce nitrile hydratase with high activity. Strain screening and optimization of fermenting conditions were further studied in ths paper, the main fruits included the following several aspects:A strain T5, which can produce nitrile hydratase, was isolated from activated sludge of wastewater treatment plant. The enzyme activity was 415.1U. After compound treatment of UV and DES to the original strain T5, the strain HUST-1 with enzyme activity of 688.3U was obtained.Based on physiological and physiochemical characteristics and 16S rDNA sequences analysis of strain HUST-1, it was identified as Rhodococcus sp.and was named as Rhodococcus sp.HUST-1.The nitrile hydratase producing conditions such as cultural temperature and pH were studied and optimized. The results showed that Co2+ and tyrosine can induce the production of nitrile hydratase. The optimum cultural medium was as follows(g/L): glucose 20, yeast extract 10, MgSO4.7H2O 0.5, K2HPO4 0.5, K2HPO4 0.5, CoCl2.6H2O 0.08mmol/L, pH 7.0. Insure the age of strain was between 36h and 48h when inoculating. In the case of 28℃and 200r/min, when HUST-1 was cultivated for 96h, the activity of nitrile hydratase was up to 1012.7U, 47.1% higher than that before optimization. By controlling pH value at about 7.0 and adding glucose and inducer in the process of fermentation, the enzyme activity was increased to 1500.4U, 48.2% higher than that before controlling.