Production of manno-oligosaccharides from locust bean gum using immobilized Penicillium occitanis mannanase

Modifying Thermostability and Reusability of Hyperthermophilic Mannanase by Immobilization on Glutaraldehyde Cross-Linked Chitosan Beads

In the current study, the purified β-mannanase (Man/Cel5B) from Thermotoga maritima was immobilized on glutaraldehyde cross-linked chitosan beads. The immobilization of Man/Cel5B on chitosan beads was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. After immobilization, the protein loading efficiency and immobilization yield were found to be 73.3% and 71.8%, respectively. The optimum pH for both free and immobilized enzymes was found to be pH 5.5. However, the optimum temperature of immobilized Man/Cel5B increased by 10 °C, from 85 °C (free Man/Cel5B) to 95 °C (Immobilized). The half-life of free and immobilized enzymes was found to be 7 h and 9 h, respectively, at 85 °C owing to the higher thermostability of immobilized Man/Cel5B. The increase in thermostability was also demonstrated by an increase in the energy of deactivation (209 kJmol⁻¹) for immobilized enzyme compared to its native form (92 kJmol⁻¹), at 85 °C. Furthermore, the immobilized Man/Cel5B displayed good operational stability as it retained 54% of its original activity after 15 repeated catalytic reactions concerning its free form.

Structural Characterization and in Vitro Fermentation of β-Mannooligosaccharides Produced from Locust Bean Gum by GH-26 endo-β-1,4-Mannanase (ManB-1601)

Size exclusion chromatography of β-mannooligosaccharides (β-MOS) mixtures, obtained from ManB-1601 hydrolysis of locust bean gum, resulted in separation of oligosaccharides with various degrees of polymerization (DP 2, 3, and 5). The oligosaccharides were structurally [ESI-MS, FTIR, XRD, TGA, and NMR (¹H and ¹³C)] and functionally (in vitro fermentation) characterized. DP2 oligosaccharide was composed of two species, (A) mannopyranose β-1,4 mannopyranose and (B) α-1,6-galactosyl-mannopyranose, while DP3 oligosaccharide showed the presence of only one species, i.e. α-d-galactosyl-β-d-mannobiose. ManB-1601 was capable of cleaving near the branch points in the substrate, resulting in oligosaccharides with galactose at the terminal position apart from attacking unsubstituted β-1,4-glycosidic linkages. DP2 and DP3 improved the growth of three out of seven species of Lactobacillus while DP5 resulted in poor growth of all Lactobacillus spp. under in vitro conditions. DP2, DP3, and DP5 were found to inhibit the growth of Escherichia coli, Listeria monocytogenes and Salmonella typhi.