Abstract
Aspergillus sp. is considered to be a good source of protease. Medium optimization is essential for each isolate in order to maximise the protease production. In the present study, different media were evaluated for maximising protease biosynthesis under submerged fermentation (SmF) using A. nidulans LCJ249 and A. flavus LCJ253. Among the six media tested, Medium 6 was found to be the best medium for maximum protease production in both A. nidulans LCJ249 (1178.0 U/mL) and A. flavus LCJ253 (950.6 U/mL). Effect of essential nutrient parameters like carbon, nitrogen and casein and other culture conditions such as incubation time, inoculum size, pH and shaking and static conditions were evaluated by the conventional one factor at a time approach. In the case of A. nidulans LCJ249, a medium containing 20 g/L glucose, 15 g/L malt extract, 5 g/L casein, initial medium pH of 7 and inoculum size of 30 mg/L favoured maximum protease production. Similarly, in A. flavus LCJ253, a medium containing 20 g/L starch, 20 g/L peptone, 15 g/L casein, initial medium pH of 7 and inoculum size of 10 mg/L favoured maximum protease production. In both the cultures, protease production was higher under shaking condition than in static conditions. The study showed that the optimised medium with optimal conditions enhanced protease production when compared to the original medium.
Highlights
Proteases hydrolyse a wide variety of proteins (Genckal and Tari, 2006)
A. nidulans LCJ249 and A. flavus LCJ253 used for this study were isolated from soil and leaf litters collected from Loyola College Campus, Chennai
The amino acids and peptides in casein may be served as specific inducers for increasing protease production by A. nidulans LCJ249 and A. flavus LCJ253
Summary
Proteases hydrolyse a wide variety of proteins (Genckal and Tari, 2006). Proteases find application in detergent, meat, protein, brewing, photographic, leather and dairy industries (Anwar and Saleemuddin, 1998). Submerged fermentation (SmF) involves the production of enzymes in liquid medium. Submerged fermentation is preferred for the production of proteases due to steady protease production, definite medium and easier downstream processing (Sandhyaa et al, 2005). Several physical and nutritional factors influence the production of protease and optimization of these factors is essential to improve the yield and make the process cost-effective (Rani et al, 2012). Optimization by conventional methods (one factor at a time) is done by varying one particular parameter at a time while keeping the other parameters constant (Wu and Hang, 2000).This method helps to assess the importance of a specific parameter on the enzyme production. The objective of our work was to optimize nutritional and physical conditions for enhancing protease production by A. nidulans LCJ249 and A. flavus LCJ253 using ‘one factor at a time’ method under submerged fermentation and scaling up of the production using the modified conditions
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