A codon-optimised 8-mannanase gene from Aspergillus niger (AnMan26) was heterologously expressed in Pichia pastoris. The peak enzyme activity of 22,100 U mL-1 was achieved in a 5-L fermenter. AnMan26 was purified to homogeneity with 1.6-fold purification via Sephacryl S100 HR gel filtration. It exhibited optimal activity at pH 5.0 and 45 ?C. AnMan26 was stable within the pH range 2.5-7.0 and exhibited good thermostability up to 40 ?C. Moreover, it revealed highest specific activity of 2869.0 U mg-1 towards locust bean gum, and efficiently degraded various mannans to manno-oligosaccharides and hydrolysed mannotetraose and mannopentaose. Furthermore, AnMan26 hydrolysed fenugreek gum to yield partially hydrolysed fenugreek gum (PHFG) with the weight-average molecular weight of 1.8 x 103 Da. The hydrolysis ratio of galactomannan in fenugreek gum was 82.2 %. Thus, an effective 8-mannanase for PHFG production was produced in this study.