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Abstract
Aspergillus fumigatus HBFH5 is a thermophilic fungus which can efficiently degrade lignocellulose and which produces a variety of glycoside hydrolase. In the present study, a novel β-mannanase gene (AfMan5A) was expressed in Pichia pastoris and characterized. AfMan5A is composed of 373 amino acids residues, and has a calculated molecular weight of 40 kDa. It has been observed that the amino acid sequence of AfMan5A showed 74.4% homology with the ManBK from Aspergillus niger. In addition, the recombined AfMan5A exhibited optimal hydrolytic activity at 60 °C and pH 6.0. It had no activity loss after incubation for 1h at 60 °C, while 65% of the initial activity was observed after 1 h at 70 °C. Additionally, it maintained about 80% of its activity in the pH range from 3.0 to 9.0. When carob bean gum was used as the substrate, the Km and Vmax values of AfMan5A were 0.21 ± 0.05 mg·mL−1 and 15.22 ± 0.33 U mg−1·min−1, respectively. AfMan5A and AfSwol showed a strong synergistic interaction on galactomannan degradation, increasing the reduction of the sugars by up to 31%. Therefore, these findings contribute to new strategies for improving the hydrolysis of galactomannan using the enzyme cocktail.
Highlights
Mannans are one of the significant hemicelluloses, and are an inexpensive and sustainable source of renewable energy, functional food and other uses [1,2]
A. fumigatus, which is widely distributed in nature, has received attention as an excellent producer of glycoside hydrolase, including amylase, tannase and cellulase
Some excellent β-mannanase obtained from A. fumigatus has been reported
Summary
Mannans are one of the significant hemicelluloses, and are an inexpensive and sustainable source of renewable energy, functional food and other uses [1,2]. They are composed of mannose, glucose and galactose by linked β-1, 4 or α-1, 6 glycosidic bonds [3,4]. The most widely known β-mannanase belong to the GH5 and GH26 families, and some of them have been cloned and functionally characterized [8] These enzymes showed optimal temperatures around 40–60 ◦ C and optimal pH around 5.0–8.0, respectively [9]. Poor tolerance and low catalytic efficiency are serious constraints to the application of β-mannanase
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