Covalent Immobilisation of an Aspergillus niger Derived Endo-1,4-β-Mannanase, Man26A, on Glutaraldehyde-Activated Chitosan Nanoparticles for the Effective Production of Prebiotic MOS from Soybean Meal

Abstract

An Aspergillus niger endo-1,4-β-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.