Penicillium citrinum: A Promising Candidate for Protease Production

Abstract

Proteases are one of the most important classes of industrial enzymes accounting for 60% of the global industrial enzyme market. Microbes are the most preferred sources of proteases because of their rapid growth, easy genetic manipulation and limited cultivation space. The aim of this study was to isolate and characterize potent fungal candidates for protease production. Protease-producing fungi were isolated from abattoir soil using standard mycological methods while screening for protease production was determined by the presence of halozones on skimmed milk agar medium. Enzyme activity using best isolate was evaluated on time course and at various pH regimes (5.0-8.0) and temperatures (25-45°C). Best isolate had halozone diameter of 69 mm and identified as Penicillium citrinum by sequencing its 18S rRNA. Optimum protease activity was recordedon the 4th day for both immobilized and free spores. When pH was optimized, pH 6 (19.25± 0.32 U/mL) and pH 6.5 (14.21 ± 0.65 U/mL) were best for immobilized and free spores respectively whereas 35°C was the best temperature condition for optimum protease activity for both immobilized (22.44 ±0.71 U/mL) and free spores (17.16 ± 0.51 U/mL). We therefore conclude that the abattoir soil environment is a potential reservoir of protease-production fungal determinants while spore immobilization resulted in better protease production.