A novel thermophilic β-mannanase with broad-range pH stability from Lichtheimia ramosa and its synergistic effect with α-galactosidase on hydrolyzing palm kernel meal

In this study, a novel GH5 family β-mannanase gene (LrMan5B) with 381 amino acid residues was identified from Lichtheimia ramosa, and highly expressed in Pichia pastoris X33. The amino acid sequence shares the highest identity (64%) with the β-mannanase from Rhizomucor miehei. Purified recombinant LrMan5B showed the optimal activity at pH 5.0 and 65 °C. It had broad-range pH stability (retaining>65% activity after incubation at pH 3.0–8.0 at 37 °C for 24 h) and was highly thermostable (retaining>80% activity after incubation at 60 °C for 30 min). LrMan5B displayed the highest catalytic efficiency for locust bean gum and the kcat/Km value was 1357.47 mL·mg-1·s-1, followed by guar gum (512.82 mL·mg-1·s-1), konjac glucomannan (454.21 mL·mg-1·s-1), and palm kernel meal (137.00 mL·mg-1·s-1). In order to evaluate the synergistic effect of LrMan5B and α-galactosidase LrAgal36A from L. ramosa, LrAgal36A was supplemented to hydrolyze palm kernel meal with LrMan5B together, showing that the reducing sugar release significantly increased by 21% (compared with the sum of that by hydrolysis of single Lrman5B or LrAgal36A). Due to its favorable enzymatic properties, LrMan5B might own potential applications in the area of food and feed processing.Graphical abstract

Source: Process Biochemistry - September 25, 2019 Category: Biochemistry Source Type: research