Strain Screening、Optimization Of Fermentation Conditions And Enzymatic Properties Of Cold-Adapted α-Mylase

α-Amylase(EC 3.2.1.1), a kind of endo-acting enzyme that hydrolyzes starch by cutting off α-1,4-glycosidic bonds at random sites. The hydrolysates include dextrin,maltose, glucose oligosaccharide, etc. α-Amylase is one of the most important commercial enzymes and is widely used in many field including starch-processing, brewing,pharmaceutical, textile, papermaking and sewage treatment.In the study, we collected samples from mud, seaweed, seafood in the sea area QinHuangdao and screened the strains that could produce α-amylase. After the study on biological characteristics and 18 SrDNA identification, the strain was named as Schwanniomyces.sp QX210. Also we got a high yied of α-amylase by exposured Schwanniomyces.sp QX210 to ultroviolate.Then the production and properties of the cold-active α-amylase produced by this strain were studied, including fermentation time, temperature, pH, carbon source and nitrogen source. Then the results were as follows. Maximum enzyme yield of 122.25U/L was achieved after 48 h cultivating. The maximum enzyme production was around 25℃with 137.32U/L enzyme yield and around pH 8.0 with 142.86U/L enzyme yield. Enzyme production was enhanced by adding of starch, beef extract and peptone. Based on the results of single factor, the maximum activity of QX210 was recorded as 167.6U/L after cultivated 48 h under the optimal condition of 0.1% soluble starch and 0.75% beef extract at 25℃.The properties of the α-amylase enzyme were studied. The optimum temperature and pH for the α-amylase activity were 35℃and 8.0, respectively. The stability of the enzyme was enhanced by Ca2+. 80% and 2% of the enzyme activity was kept after 4h of incubation at 25℃ and 45℃, respectively. The amylase was highly stable in the range of pH 7.5 to8.5 at 30℃ for 1h. The enzyme was activated by K+, Na+, Ca2+ and strongly inhibited by Cu2+ and Fe3+.