Two Novel Thermal Stable Pectate Lyases from Dickeya dadantii DCE-01: Cloning, Expression and Characterization

D. dadantii DCE-01 is an available and efficient strain of bacteria for bast fiber degumming. Pectate lyase genes (pelB and pelC) were cloned from the genome of D. dadantii DCE-01 and overproduced in Escherichia coli BL21 (DE3). Using polygalacturonic acid sodium (PGA center dot Na) as a substrate, maximum pectate lyase activities in fermentation liquor of E. coli harboring the pelB and pelC reached 1374.2 IU/mg and 231.8 IU/mg respectively. Purified by a two-step process involving ultrafiltration and gel filtration, the PelB and PelC exhibited corresponding molecular masses about 37.8 kD and 38.1 kD on SDS-PAGE. For the purified PelB, optimal pH and temperature exhibited 9.0 and 50 degrees C respectively. A high activity and stability were showed when temperature was higher than 45 degrees C in pH 8.5-10.0 and the highest affinity was displayed for PGA center dot Na (nonmethylated substrate). For the purified PelC, optimal pH and temperature were 9.5 and 55 degrees C respectively, thermal stability and alkaline-stability were showed up to 60 degrees C in pH 9.0-10.0, and the optimal substrate was apple pectin (partially methylated substrate). The high yield of the extracellular activities, relevant alkaliphilicity and thermostability of the two Pels suggest potential implications for textile application.