The Increase of Incomplete Degradation Products of Galactomannan Production by Synergetic Hydrolysis of β-Mannanase and α-Galactosidase

Study on structure and properties of galactomannan and enzyme changes during fenugreek seeds germination

Fenugreek (Trigonella foenum-graecum L) galactomannan play an important role in the food and pharmaceutical sectors due to its attractive physicochemical properties. In this study, the changes of structure, properties and biological activity of fenugreek galactomannan (FG) during germination are analyzed by the activity and mechanism of endogenous enzymes (α-D-galactosidase and β-D-mannanase). The enzymes generally increased during germination and synergistically altered the structure of GM by cutting down the main chains and removing partial side residues. The mannose to galactose ratio (M/G) increased from 1.11 to 1.59, which is accompanied by a drastic decrease in molecular weight from 3.606 × 106 to 0.832 × 106 g/mol, and the drop of viscosity from 0.27 to 0.06 Pa·sn. The degraded macromolecules are attributed to the increase in solubility (from 64.55 % to 88.62 %). In terms of antioxidation and antidiabetic ability, germinated fenugreek galactomannan has the ability to scavenge 67.17 % ABTS free radicals and inhibit 86.89 % α-glucosidase. This galactomannan with low molecular weight and excellent biological activity precisely satisfies the current demands of pharmaceutical reagents and food industry. Seeds germination holds promise as a means of industrial scale production of low molecular weight galactomannans.

Production and characterization of thermostable acidophilic β-mannanase from Aureobasidium pullulans NRRL 58524 and its potential in mannooligosaccharide production from spent coffee ground galactomannan

The maximum yield of the crude mannanase from Aureobasidium pullulans NRRL 58524 was 8.42 ± 0.18 U mL-1 when cultured for 72 h in the optimized medium containing 3% (w v-1) defatted spent coffee grounds (SCG) and 0.67% (w v-1) ammonium sulphate. Two forms of mannanase were observed in the crude enzyme and the principal mannanase was enriched to apparent homogeneity via sequential filtration and anion exchange chromatography. The molecular mass of the enzyme was approximately 63 kDa as determined by SDS-PAGE. The enriched mannanase was active at high temperatures (45-75 °C) and a pH range from 3 to 6 with the maximum activity at 55 °C and pH 4.0. The enzyme was relatively thermostable with more than 75% of its initial activity remained after a 12 h incubation at 55 °C. The half-lives of the enriched mannanase were over 8 and 6 h at 60 and 65 °C, respectively. The enzyme was not adversely affected by chelator and most ions tested. This enzyme could hydrolyze both glucomannan and galactomannan and exhibited limited catalytic activity on beta-glucan. When the crude mannanase was used to hydrolyze galactomannan extracted from SCG, the maximum yield of reducing sugars mainly comprising of mannobiose (16.27 ± 0.84 mg 100 mg-1), and mannotriose (2.85 ± 0.20 mg 100 mg-1) was obtained at 58.22 ± 2.04 mg 100 mg-1 dry weight, under optimized condition (84.87 U g-1 mannanase, 41 h 34 min incubation at 55 °C and pH 4.0). These results suggested the prospect of the enzyme in mannan hydrolysis and mannooligosaccharide production at a larger scale.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03301-4.

Using One-pot Fermentation Technology to Prepare Enzyme Cocktail to Sustainably Produce Low Molecular Weight Galactomannans from Sesbania cannabina Seeds

Enzymatic hydrolysis using β-mannanase and α-galactosidase is necessary to produce low molecular weight galactomannan (LMW-GM) from galactomannans (GM) in the leguminous seeds. In this study, different ratios of avicel and melibiose were used as the inductors (carbon sources) for Trichoderma reesei to metabolize the enzyme cocktail containing β-mannanase and α-galactosidase using one-pot fermentation technology. The obtained enzyme cocktail was used to efficiently produce LMW-GM from GM in Sesbania cannabina seeds. Results showed that 15 g/L avicel and 10 g/L melibiose were the best carbon sources to prepare enzyme cocktail containing β-mannanase and α-galactosidase with activities of 3.69 ± 0.27 U/mL and 0.51 ± 0.02 U/mL, respectively. Specifically, melibiose could effectively induce the metabolite product of α-galactosidase by T. reesei, which showed good performance in degrading the galactose substituent from GM backbone. The degradation of galactose alleviated the spatial site-blocking effect for enzymatic hydrolysis by β-mannanase and improved the yield of LMW-GM. This research can lay the foundation for the industrial technology amplification of LMW-GM production for further application.

A Thermophilic GH5 Endoglucanase from Aspergillus fumigatus and Its Synergistic Hydrolysis of Mannan-Containing Polysaccharides

In this study, we isolated and identified a thermophilic strain of Aspergillus fumigatus from the “Daqu” samples. Transcriptomic analysis of A. fumigatus identified 239 carbohydrate-active enzymes (CAZy)-encoding genes, including 167 glycoside hydrolase (GH)-encoding genes, 58 glycosyltransferase (GT)-encoding genes, 2 polysaccharide lyase (PLs)-encoding genes and 12 carbohydrate esterase (CEs)-encoding genes, which indicates that the strain has a strong potential for application for enzyme production. Furthermore, we also identified a novel endoglucanase gene (AfCel5A), which was expressed in Pichia pastoris and characterized. The novel endoglucanase AfCel5A exhibited the highest hydrolytic activity against CMC-Na and the optimal activity at 80 °C and pH 4.0 and also showed good stability at pH 3.0–11.0 and below 70 °C. The Km and Vmax values of AfCel5 were 0.16 ± 0.05 mg·mL−1 and 7.23 ± 0.33 mol mg−1·min−1, respectively, using CMC-Na as a substrate. Further, the endoglucanase exhibited a high tolerance toward NaCl as well as glucose. In addition, the finding that the endoglucanase AfCel5A in combination with β-mannanse (ManBK) clearly increased the release of total reducing sugars of glucomannan by up to 74% is significant.