Hydrolysis of palm kernel meal fibre using a newly isolatedBacillus subtilisF6 with high mannanase activity

Abstract

AbstractHigh fibre content is the main limitation of using mannan-rich palm kernel meal (PKM) in feeding non-ruminant livestock. Microbial fermentation stands out as a cost-effective and environmentally friendly approach for hydrolysing fibre in lignocellulosic biomass. In this study, aBacillus subtilisstrain F6 with high mannanase secretion capability was isolated from an environmental source. Fermentation of PKM using strain F6 resulted in at least a 10% reduction in its neutral detergent fibre content. Notably, the strain exhibited a rapid response to PKM, with significant mannanase activity detected as early as 6 h, enabling fibre hydrolysis within a short fermentation period. Subsequent transcriptome analysis uncovered potential enzymes involved in PKM fibre degradation, and the purified recombinant enzymes were generated to assess their activity on PKM fibre degradation. β-mannanase GmuG demonstrated strong hydrolysis activity of PKM fibre, and its biochemical properties were determined. Overall, the study reported the isolation of aB. subtilisstrain suitable for fibre hydrolysis of mannan-rich biomass, followed by an investigation to identify and characterize the enzyme responsible for fibre degradation.Graphical abstract