Screening,Cloning and Expression of Aspergillus niger β-glucosidase

From the 10 strains of Aspergillus,the strain A.niger FTA-008 was selected and it possessed highβ-glucosidase activity(2.89 U/mL).The period ofβ-glucosidase production by this strain was 3 days.A set of primers were synthesized based on the sequence ofβ-glucosidase gene(bgl1)(AJ132386)of A.niger.The cDNA fragment was amplified with RT-PCR using the total RNA of A.niger FTA-008 as template.The cloned gene fragment was 2 511 bp.Compared with sequence AJ132386, the identity of amino acid sequence was 96.8%.The cDNA was successfully expressed in Pichia pastoris and the maximum β-glucosidase activity(7.85 U/mg)was achieved in the BMMY medium containing 0.5%methanol and 240 r/min at pH 6.0 under 30°C for 108 h.Fig 3,Tab 1,Ref 13