Preparation of low-molecular-weight citrus pectin by recombinant Bacillus subtilis pectate lyase and promotion of growth of Bifidobacterium longum

Abstract pel gene (GenBank: KM244046.1 ), which encodes Bacillus subtilis pectate lyase (PelB), was high-level expressed in Escherichia coli BL21 (DE3) and the recombinant enzyme was named rePelB. After induction by IPTG at 15 °C for 24 h, specific activity of rePelB in culture supernatant of pCpel-6 reached 197.4 ± 5.20 U/mg. The optima of rePelB were 60 °C and pH 5.0, respectively. Hydrolysis of citrus pectin by rePelB in 50 L grass reactor was optimized by implementing RSM. HPLC analysis revealed molecular mass of citrus pectin and obtained LCP was 290 and 5.8 kDa, respectively. LCP can significantly promote growth of Bifidobacterium longum.