Study On Biological Characteristics Of Cold-active-phytase-producing Strains

The purpose of this paper was to screen high-yielding strains of phytase, and in order tostudy its biological characteristics, including not only the classification and identification ofstrain, but also enzymatic properties and fermentation conditions of the cold-active phytaseproducing by the screened strain.1. The sequence of Internal Transcriber Spacer rDNA (ITS rDNA) from genome DNA ofstrain CZC0208which was preserved in our laboratory, was analyzed and built NJphylogenetic tree. The result showed CZC0208was belonged to Dipodascus. Because ofphytase production of CZC0208was became lower, ultraviolet mutagenesis to CZC0208wastaken for many times. But mutant strain with much higher phytase production wasn’t got.Therefore, it is necessary for screening high-yielding cold-active phytase strains.2.7strains producing cold-active phytase were isolated from seawater and sea mud, soilsamples, and so on. According to the determination of enzyme activity, the cold-activephytase, from strain CZC0806isolated from seawater, had highest activity. CZC0806waspreliminarily identified as Kurthia by morphology of strain CZC0806and NJ phylogenetictree based on the result of16s rDNA. The properties of the cold-active phytase from strainCZC0806was preliminary studied, and results were as follows: The optimum temperature andpH of the cold-active phytase were35℃and5.5respectively; and metal ions had little effecton its activity. Based on the single-factor and response surface analysis, optimization resultsof fermentation medium components of strain CZC0806showed: sucrose3.38%, peptone0.99%, NaCl0.82%, CaCl2·2H2O0.07%, MgSO4·7H2O0.03%, FeSO4·7H2O0.007%. Andbased on the single-factor and orthogonal experiments, optimization results of its fermentationconditions showed: initial pH7.0,20℃, seed volume8%for55hours,180r/min.The highestyield of enzyme was up to114.51U/mL...