PRODUCTION OF NEUTRAL PROTEASES BY SERRATIA MARSCENS USING RICE BRAN

Abstract

For the utilization of rice bran, a cheap and widely available agricultural by-product, to produce extracellular protease enzyme, Serratia marscens isolated from soil and skim milk was used. Studies of nutritional factors for getting the optimal composition of rice bran me- dia showed that 33 % (v/v) rice bran hydrolysate (6% carbon)' 0.06% N-source (4.3% potassium nitrate) and 1% NaH2PO4 gave the highest yield. The highest proteolytic activity in the culture supernatant (650 T.U./ml) deter- mined after 72 h incubation at 35 ° C and 120 rpm, was obtained when the strain had been grown in natural medium. Optimum temperature for production of protease was found to be :35 °C whereas maximum activity was recorded at 30°C and pH 7.5. Based on the EDTA sensitivity and its neutral pH spectrum, the protease of S. marscens may be classified as neutral protease.