Abstract
Rare actinobacteria have received significant attention which are commonly categorized as strains other than Streptomyces or isolates with less frequency of isolation under normal parameters. These rare actinomycetes may produce important enzymes and some antibiotics. L-glutaminase is an amidohydrolase, produced by a variety of microorganisms including bacteria, yeast and fungi and catalyzed the deamination of L-glutamine to glutamic acid and ammonia. It has extensive applications as an antitumor agent. About 11 actinomycetes isolates were obtained from saline water from the Red Sea Coast on starch nitrate agar containing 10 % NaCl and some antibiotics (25 mu g /ml nystatin, 25 mu g/ml novobiocin and 25 mu g/ml cycloheximide. at 45 degrees C. All the isolates were screened for L- glutaminase production using phenol red as indicator. Out of 11 isolates, 5 showed excellent production and the isolate MM11 was the most active one. According to morphological and physiological characters, it was identified as identified as species of genus Streptomyces. Identification was confirmed using 16SrDNA and the isolate was identified as Streptomyces sp. MM11 and was similar to Streptomyces barkulensis strain RC1831 with 95% similarity level. Thus, it was identified as Streptomyces barkulensis MM11. Maximal enzyme production was detected in medium containing L-glutamine as carbon and nitrogen sources, respectively at pH 9.0, 40 degrees C and after 7 days. It was clear that addition of yeast extract decreased the enzyme production. The enzyme was collected; partially purified using column chromatography. The molecular weight was determined to be 44 kD. Brine shrimp lethality test was used to predict the cytotoxic effect of the L-glutaminase. The obtained enzyme showed no toxicity and excellent antitumor activities against two cancer cell lines. In conclusion, using submerged fermentation, L-glutaminase was produced by Streptomyces barkulensis MM 11 using maltose and glutamine as carbon and nitrogen sources and optimizing the growth conditions enhanced the enzyme production which can be used as antitumor agent with no toxicity.