Screening and identification of phospholipase-producing strains and their applications

Using soybean phospholipids as substrates, one strain which expressed phospholipase was screened out from the oil-rich soil sample by preliminary screening of plate cultivation and re-screening of shake flask fermentation. According to the morphological characteristics, physiochemical properties, and 16S rRNA sequences, the strain BIT-18 was identified as Pseudomonas fluorescens. Synthetic phosphatecholine (1-palmitoyl-2-oleoyl phosphatecholine) was used as substrate, then the fatty acid compositions of hydrolyzates were analyzed by gas chromatography, and the phospholipase from BIT-18 was determined as phospholipase B. This enzyme could not tolerate a high temperature. The optimal conditions for the enzymatic reaction were 25°C and pH 6.5, and low concentrations of metal ions were good for trigging its reaction. The phospholipase B from BIT-18 was used as catalyst for the degumming of soybean oil in a self-made batch reactor. The optimal conditions were phospholipase B dosage of 500 U·kg ^-1 and 2% water, and reaction at 40°C, pH 4.7 for 6 h. The residual phosphorus content of degummed oil decreased from 90.1 mg·kg ^-1 to 4.6 mg·kg ^-1, with the degumming rate as high as 94.9%, which showed a good application potential in the degumming of vegetable oils.