Increased production of alkaline polygalacturonate lyase in the recombinant WB43CB by optimizing the medium

Alkaline polygalacturonate lyase (PGL), which was the central enzyme of green environmental enzyme treatment technology, has been widely used in textile, papermaking and beverage production. In the previous work, Bacillus subtilis was used as the expression host, and the PGL gene derived from B. subtilis WSHB04-02 was successfully expressed in the engineered strain WB43CB by regulating of molecular elements such as signal peptide, promoter and SD sequence. In this study, the fermentation medium was optimized from four aspects of carbon source, nitrogen source, liquid volume and inoculum volume, and the extracellular PGL enzyme activity in WB43CB increased from 264.5 U·mL-1 to 461.96 U·mL-1, which laid a solid foundation for the industrial production of PGL.

High PGL productivity in Bacillus subtilis by optimizing the SD sequence

Alkaline polygalacturonate lyase (PGL, EC 4.2.2.2) can catalyze the cleavage of a-1, 4-glycosidic bonds of polygalacturonate by a trans-elimination reaction and generate an unsaturated oligogalacturonates. As the critical enzyme of many environmental friendly processes, alkaline PGL has been widely used in many fields including paper, textile and beverage industries. At present, Bacillus subtilis is an ideal strain for producing PGL, but the yield is too low for industrial production. In this study, the effect of different SD sequences on the production of PGL was comparatively investigated, and the strong SD sequence (AGAGAACAAGGAGGG G) directed efficient PGL secretory expression and increased PGL yield to 264.5 U·mL-1 with a high productivity. As a result, the PGL yield in B. subtilis was effecively increased and laid the solid foundation for PGL industrial production.

Optimizing Culture Conditions by Statistical Approach to Enhance Production of Pectinase from Bacillus sp. Y1

It was found that Bacillus sp. Y1 could secrete alkaline pectinase with suitable enzyme system for powerful and fast degumming of ramie fiber. In this study, the medium components and fermentation conditions were optimized by some statistical methods including mixture design, fractional factorial design, central composite design and response surface methodology, and single factor method for enhancing the alkaline pectinase production. The optimized conditions for pectinase production were that the culture was shaken at 34°C for 60 h in 50 mL of medium containing 10.5% (w/v) carbon source (consisting of 3.8% starch, 4.2% wheat bran, and 2.5% sucrose), 0.37% (NH4)2SO4, 0.3% MgSO4, and 0.1% Tween-80, with initial pH 8.2 and inoculation amount of 1.3 mL (with the OD600 of the seed medium about 5.77). Using the optimizing conditions, the activities of polygalacturonate lyase (PGL) and polygalacturonase (PG) in fermentation liquor were increased to 2.00-fold and 3.44-fold, respectively, and the fermentation time shortened 12 hours (from 72 h to 60 h), which showed good application potential in degumming of ramie.