Optimization of Fermentation Conditions of A Protease-Producing Strain Planomicrobium sp.L-2

A protease-producing strain Planomicrobiumsp.L-2was isolated and identified from gastrointestinal tract of Octopus variabilis.To increase the yield of proteases in Planomicrobiumsp.L-2,the optimal fermentation conditions for producing protease,including carbon source,nitrogen source,fermentation time,fermentation temperature,initial pH value of medium,and inoculum amount were studied by single factor experiments.On the base of that,response surface analysis was applied to optimize the compositions of fermentation medium of Planomicrobiumsp.L-2for producing protease.The optimal medium was composed of soluble starch0.73%,peptone 0.68%,yeast extract 0.15%,FePO40.01%in sea water with the initial pH value of 8.0.And then the medium with 8%inoculum amount was cultured at 25℃for 3.5d.Under these optimal conditions,the activity of proteases produced by Planomicrobiumsp.L-2was high up to 1 457U·mL-1,which was approximately 2times higher than that of the original condition.