Screening and identification of pectinase-producting strains and optimization of pectinase-producting condition

To obtain the pectinase- producing strains, the bromophenol blue plate separation method which contains the pectin as the sole carbon source was used,combined with DP/DCvalue and flat color changes. The strains screened were inoculated for the liquid fermentation culture,and the activities were determinated,then screened again out a strain XHV25 with the pectinase activity of 2937.34 U/m L. Morphology,physiology and biochemistry research coupled with 18 S r RNA,ITS,26 S r RNA sequence and analysis indicates that the strain of XHV25 was Zygoascus sp. Single-factor method was used for optimizing the fermentation condition. The optimum pectinase-producting conditions were as follows :initial medium p H5.5,shaking speed 160 r/min,inoculum amount 4%(v/v),loading volume 25 m L/250 m L,optimum fermentation temperature 31 ℃,fermentation time 48 h.Under this fermentation conditions,pectinase activity reached 4849.90 U/m L,which was 65.11% higher than that of before optimization.