A solvent-stable metalloprotease produced by Pseudomonas aeruginosa A2 grown on shrimp shell waste and its application in chitin extraction.

A solvent-stable protease-producing bacterium was isolated and identified as Pseudomonas aeruginosa A2. The strain was found to produce high level of protease activity when grown in media containing only fresh shrimp waste (FSW) or shrimp waste powder (SWP), indicating that it can obtain its carbon, nitrogen, and salts requirements directly from shrimp waste. Maximum protease activities 17,000 and 12,000 U/mL were obtained with 80 g/L SWP and 135 g/L FSW, respectively. The optimum temperature and pH for protease activity were 60 °C and 8.0, respectively. The crude protease, at different enzyme/substrate (E/S) ratio, was tested for the deproteinization of shrimp waste to produce chitin. The crude enzyme of P. aeruginosa A2 was found to be effective in the deproteinization of shrimp waste. The protein removals after 3 h hydrolysis at 40 °C with an E/S ratio of 0.5 and 5 U/mg protein were about 56% and 85%, respectively. (13)C CP/MAS-NMR spectral analysis of the chitin prepared by treatment with the crude protease was carried out and was found to be similar to that of the commercial α-chitin. These results suggest that enzymatic deproteinization of shrimp waste by A2 protease could be applicable to the chitin production process.