High-level expression and characterization of a novel phospholipase C from Thielavia terrestris suitable for oil degumming

Abstract

A novel phospholipase C gene (TtPLC) from Thielavia terrestris CAU709 was cloned and efficiently expressed in Pichia pastoris. The deduced protein sequence of TtPLC shared the highest identity of 33% with the characterized phospholipase C from Arabidopsis thaliana. The highest phospholipase C yield of 98, 970 U mL−1, with a protein concentration of 4.9 mg mL−1 was obtained by high-cell density fermentation in a 5-L fermentor. The recombinant enzyme (TtPLC) was purified to homogeneity with a recovery yield of 59.1% and a specific activity of 22, 910 U mg−1. TtPLC was most active at pH 6.5 and 55 °C, respectively. It was stable within the pH range of 4.5–8.0 and up to 45 °C. The enzyme exhibited excellent stability in different surfactants and organic solvents, including Tween 20 (147.6%), Tween 40 (180.6%), Tween 60 (205.4%), cyclohexane (160.0%), n-octane (178.2%), n-heptane (180.7%), acetone (187.5%) etc. The application of TtPLC in crude soybean oil degumming process significantly reduced the residual phosphorus content from 135.4 mg kg−1 to 7.9 mg kg−1 under the optimized conditions, which satisfied the requirement of environmental friendly physical refining process for oil refining industry. Therefore, TtPLC should be a good candidate in oil refining industry.