OPTIMIZATION OF SOME CULTURE CONDITIONS FOR A MARINE BACTERIUM ACINETOBACTER SP. QN6 PRODUCING PROTEASE

Abstract

From seawater samples in different sea sites of Vietnam, 3S marine strains indicating protease activity were isolated. Among them, the marine strain QN6 was the best protease producer (0.633 U/ml). Nucleotide sequence of 16S rDNA of the strain QN6 showed that this strain belonged to Acinetobacter genus and deposited in GenBank with the accession number DQ640274 (Acinetobacter sp. QN6). Several culture conditions for cell growth and protease production of the strain Acinetobacter sp. QN6 were determined. The cell growth of the strain QN6 exhibited maximum (ODoooom: 3.9) after 48 hours of cultivation at 30·C in LB medium pH 7.0 supplemented with 20% (v/v) of seawater. The extracellular protease was produced highest after 28 hours of cultivation (0.51 U/ml). Lactose and yeast extract were the best carbon sources for both cell growth and protease production (OD600om: 3.2 and 0.433 U/ml, and OD"", om: 3.6 and 0.509 Ulml, respectively). The best nitrogen source for cell growth and protease production was peptone, OD,oo =: 3.5 and 0.359 Vim\. The optimal temperature for cell growth and  protease production was 30'C with OD600 om: 3.3 and 0.387 VIm!. The optimal pH for cell growth was pH 6.5 while for protease production was pH 7.0 (0.441 Vlml). The addition of 4% (w/v) of casein was optimum for cell growth (OD600 om: 4.8) while 1% (w/v) of casein was the optimum for protease production (0.613 Vlml).