Abstract:
An Aspergillus niger endo-1,4- -mannanase, Man26A, was confirmed by FTIR and XRD
to be immobilised on glutaraldehyde-activated chitosan nanoparticles via covalent bonding. The
immobilisation (%) and activity yields (%) were 82.25% and 20.75%, respectively. The biochemical
properties (pH, temperature optima, and stability) were then comparatively evaluated for both the free
and immobilised Man26A. The optimal activity of Man26A shifted to a lower pH after immobilisation
(pH 2.0–3.0, from pH 5 for the free enzyme), with the optimum temperature remaining unchanged
(60 C). The two enzymes exhibited identical thermal stability, maintaining 100% activity for the first
6 h at 55 C. Substrate-specific kinetic analysis showed that the two enzymes had similar affinities
towards locust bean gum (LBG) with varied Vmax values. In contrast, they showed various affinities
towards soybean meal (SBM) and similar Vmax values. The immobilised enzyme was then employed
in the enhancement of the functional feed/prebiotic properties of SBM from poultry feed, increasing
mannooligosaccharides (MOS) quantities. The SBM main hydrolysis products were mannobiose
(M2) and mannose (M1). The SBM-produced sugars could be utilised as a carbon source by probiotic
bacteria; Streptococcus thermophilus, Bacillus subtilis, and Lactobacillus bulgaricus. The results indicate
that the immobilised enzyme has the potential for use in the sustainable and cost-effective production
of prebiotic MOS from agricultural biomass.
