Characterization of a Novel Thermophilic Mannanase and Synergistic Hydrolysis of Galactomannan Combined with Swollenin

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 beta-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 degrees C and pH 6.0. It had no activity loss after incubation for 1h at 60 degrees C, while 65% of the initial activity was observed after 1 h at 70 degrees 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 center dot mL(-1) and 15.22 +/- 0.33 U mg(-1)center dot 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.

Automated summary

The novel beta-mannanase gene AfMan5A from Aspergillus fumigatus HBFH5 has been successfully expressed and characterized in this study. AfMan5A shows potential for efficiently hydrolyzing galactomannan with good thermal stability and pH adaptability. Furthermore, AfMan5A and AfSwol exhibit a strong synergistic interaction, leading to increased efficiency in galactomannan degradation.