Efficient production of recombinant tannase in Aspergillus oryzae using an improved glucoamylase gene promoter

A tannase-encoding gene, AotanB, from Aspergillus oryzae RIB40 was overexpressed in A. oryzae AOK11 niaD-deficient mutant derived from an industrial strain under the control of an improved glucoamylase gene promoter PglaA142. The recombinant tannase, designated as rAoTanBO, was produced efficiently as an active extracellular enzyme. Purified rAoTanBO showed a smeared band with a molecular mass of approximately 80–100 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The rAoTanBO had a molecular mass of 65 kDa, after treatment with endo-β-N-acetylglucosaminidase H. Purified rAoTanBO exhibited maximum activity at 30–35°C and pH 6.0. The tannase activity of purified rAoTanBO towards natural and artificial substrates was 2–8 folds higher than that of the recombinant enzyme produced by Pichia pastoris, designated as rAoTanBP. N-terminus of the mature rAoTanBP had six more amino acids than the N-terminus of the mature rAoTanBO. Kinetic analyses showed that rAoTanBO had higher catalytic efficiency (kcat/Km) than rAoTanBP. rAoTanBO was stable up to 60°C and higher thermostability than rAoTanBP. N-linked oligosaccharides had no effect on the activity and stability of rAoTanBO and rAoTanBP. [Display omitted] •A tannase-encoding gene AotanB was overexpressed in Aspergillus oryzae using the promoter PglaA142.•The production of rAoTanBO by A. oryzae was more efficient than that of rAoTanBP by Pichia pastoris.•The tannase activity and thermal stability of the purified rAoTanBO were higher than those of the purified rAoTanBP.•N-terminus of the mature rAoTanBP had more six amino acids than the N-terminus of the mature rAoTanBO.