Hydrolysis of palm kernel meal fibre using a newly isolated Bacillus subtilis F6 with high mannanase activity

Abstract

High 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, a Bacillus subtilis strain 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. {beta}-mannanase GmuG demonstrated strong hydrolysis activity of PKM fibre, and its biochemical properties were determined. Overall, the study reported the isolation of a B. subtilis strain suitable for fibre hydrolysis of mannan-rich biomass, followed by an investigation to identify and characterize the enzyme responsible for fibre degradation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=146 SRC="FIGDIR/small/599806v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@50b8c8org.highwire.dtl.DTLVardef@1937688org.highwire.dtl.DTLVardef@4b0ab6org.highwire.dtl.DTLVardef@ac727a_HPS_FORMAT_FIGEXP M_FIG C_FIG