Over 60% of the global productions of industrial enzymes are proteolytic enzymes in which about 35% are alkaline proteases. The current microbial sources are unable to reach industrial demands of alkaline protease which led scientists to search new sources with enhanced enzyme activity. Therefore, we applied UV irradiation to develop a Pseudomonas aeruginosa mutant as a new source of enhanced protease activity, followed by cultural and nutritional optimization. The mutagenesis was carried out by exposing parent strains to UV radiation (30w, 2537 Å) at 25 ºC with a different time interval. The protease activity was estimated as relative protease activity and standard protease assay (OD660). Among all, mutant strain P. aeruginosaM25 (PA-M25) exhibited 75.47% increased protease activity over the parent strain in submerged fermentation. It showed 612.84±2.50 U/ml of alkaline protease production compared to 349.26±2.57 U/ml by wild-type strain (significant at P≤0.005). Besides, the effects of nutritional factors on the protease production by PA-M25 were also studied. We found the optimal alkaline protease production in the medium (adjusted to pH 9.0) supplemented with 1% (w/v) glucose as carbon source, 0.5% (w/v) casein as nitrogen source and 2% (w/v) NaCl when incubated at 35 ºC for 48 h without agitation. We believe that the mutant PA-M25 could be a potential candidate to meet the growing protease demands. However, further assessments regarding the characterization of the protease enzyme, as well as the industrial fitness of the mutant, are warranted.
Key words: Alkaline protease, Pseudomonas aeruginosa, Protease assay, Mutagenesis, UV irradiation
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