Heterologous expression and characterization of novel glucomannan-degrading enzymes from Paenibacillus macerans

Abstract:

[Objective] We cloned, expressed, and characterized the glucomannan-degrading enzymes from Paenibacillus macerans, aiming to enrich the glucomannan-degrading enzyme resources and decipher the mechanism of glucomannan degradation by P. macerans. [Methods] We retrieved the glucomannan-degrading enzyme genes and constructed recombinant strains to express the recombinant enzymes. The roles of the purified proteins in the degradation of glucomannan were then studied. [Results] We cloned and expressed five glucomannan-degrading enzymes, among which PmMan1 and PmMan2 were endo-β-mannanases, and PmGlc1, PmGlc2, and PmGlc3 were exo-β-glucosidases. PmGlc1 only hydrolyzed pNPβGlc, and PmGlc2 hydrolyzed β-1,6-glucosidic bonds in disaccharides and ginsenosides. PmGlc3 hydrolyzed a wide range of β-glucosidic bonds. PmMan1, PmMan2, PmGlc2, and PmGlc3 degraded glucomannan oligosaccharides, and PmMan1 and PmMan2 degraded glucomannan. In the degradation of glucomannan, PmGlc2 and PmGlc3 had synergistic effects with PmMan2, and the synergistic effect was more significant between PmGlc3 and PmMan2. [Conclusion] We obtained four glucomannan-degrading enzymes from P. macerans and clarified the role of the enzymes in glucomannan degradation. The findings enrich the enzyme resources and theoretical research achievements and provide an effective tool for enzymatic preparation of active glucomannan oligosaccharides.