Abstract: A protease-producing bacterial strain was isolated and screened from the intestine of Octopus vulgaris by detecting hydrolysis circle of protease and its activity and identified as QDV-3. The optimal fermentation conditions for protease production and its enzymatic properties were also investigated. The highest protease production was achieved when strain QDV-3 was cultured at 30 ℃ for 3.5 d under shaking conditions in a medium at pH 8.0 with fructose as the carbon source and peptone as the nitrogen source. Meanwhile, protease production was improved in the presence of Mn2+ and Ba2+. At least five proteases were identified by SDS-PAGE, with molecular weights between 32.4 kD and 124.2 kD. The optimal reaction temperature and pH for the fermentation supernatant were 50—60 ℃ and 9—11, respectively. The fermentation supernatant exhibited high thermal stability, and 95% of its initial activity was retained after 1 h incubation at 50 ℃.

Key words: protease-producing bacterial strain, protease, enzymatic properties