Characterization and overproduction of a thermo-alkaline pectate lyase from alkaliphilic Bacillus licheniformis with potential in ramie degumming

A thermo-alkaline pectate lyase (BliPelA) gene from an alkaliphilic Bacillus licheniformis strain was cloned and overexpressed in Escherichia coli. Mature BliPelA exhibited maximum activity at pH 11 and 70 degrees C, and demonstrated cleavage capability on a broad range of substrates such as polygalacturonic acid, pectins, and methylated pectins. The highest specific activity, of 320 U mg(-1), was towards polygalacturonic acid. Significant ramie (Boehmeria nivea) fiber weight loss (21.5%) was obtained folloWing enzyme treatment and combined enzyme-chemical treatment (29.3%), indicating a high ramie degumming efficiency of BliPelA. The total activity of recombinant BliPelA reached 1450.1 U ml(-1) with a productivity of 48.3 U ml(-1) h(-1) under high-cell-density cultivation with a glycerol exponential feeding strategy for 30 h in 1-l fed-batch fermenter, and 1380.1 U ml(-1) With a productivity of 57.5 U ml(-1) h-1 after 24 h under constant glucose feeding in a 20-l fermenter using E. coli as the host. The enzyme yields reached 4.5 and 4.3gl(-1) in 1-l and 20-l fed-batch fermenters, respectively, which are higher than those of most reported alkaline Pels. Based on these promising properties and high-level production, BliPelA shows great potential for application in ramie degumming in textile industry. (C) 2017 Published by Elsevier Ltd.