Thermostable acidic protease production in Aspergillus terreus NCFT 4269.10 using chickling vetch peels

A newly isolated fungus, Aspergillus terreus NCFT4269.10, was employed in both solid state (SSF) and liquid static surface culture (LSSC) for the production of protease using different agro-residues. Among different substrates appraised, chickling vetch peels (CVP) supported the enhanced production of protease both at LSSC and SSF (499.99 ± 11 U/ml; 5266.8 ± 202.5 U/gds, respectively). In the presence of peptone (1%, w/v), leucine (5 mM/100 ml), Fe2+ (1 mM) and riboflavin (10 mg/100 ml) with a medium pH of 5.0 incubated at 30 °C for 96 h, 3-fold higher protease production was achieved in LSSC compared with control. Fermentation kinetics studies revealed that the highest specific growth rate of A. terreus was observed in fermentation medium supplemented with riboflavin (10 mg/100 ml), i.e., 256.45 mg l−1 h−1. The growth-associated coefficient of enzyme production (α) by A. terreus was maximal when protease was produced using Fe2+. Further, the protease was purified to electrophoretic homogeneity and its molecular mass was determined as 23.8 kDa. The present strain suggests the potential utilization of inexpensive agro-residues (CVP) as medium components for the efficient industrial production using LSSC.