ABSTRACT
In this report, the halotolerant bacterium Halomonas sp. BRI3 was studied for its biosurfactant (BS) producing ability. Effect of carbon source, nitrogen source, temperature, inoculum concentration and incubation on the production of BS was studied and maximum production (14 g/L) was obtained in modified medium containing 1% glucose, yeast extract and ammonium chloride (0.25% each) with 5% inoculum concentration at 30°C after 48 h, which was 2.8 fold higher as compared to original medium (5 g/L). Highest emulsification index (72%) of crude BS was obtained with kerosene followed by n-hexane > crude oil > n-heptane > soybean oil > hexadecane > mustard oil > olive oil > sesame oil. Our hydrocarbon degradation experiments using crude oil and soybean oil revealed 40% decrease in crude oil and 60% decrease in soybean oil concentration after 50 days in presence of glucose, whereas, it was 20% and 50% in the absence of glucose, respectively. Based on TLC and FTIR analysis, the BS is chemically a glycolipo protein, demonstrated an significant antimicrobial and antiadhesive activity. We observed significant stability of BS over wide range of temperature (40 to 120°C) and pH (5.0 to 11.0), suggesting its potential for application in food, pharmaceutical and cosmetics industries.
ABSTRACT
Out of the vast pool of enzymes, proteolytic enzymes from microorganisms are the most widely used in different industries such as detergent, food, peptide production etc. Several marine microorganisms are known to produce proteases with commercially desirable characteristics. We have isolated nine different cultures from marine samples of the Indian Ocean. All of them were i) motile ii) rod shaped iii) non spore forming iv) catalase and amylase positive v) able to grow in presence of 10 percent NaCl. They produced acid from glucose, fructose and maltose and grew optimally at 30 0C temperature and pH 7.0-8.0. None of them could grow above 45 0C and below 15 0C. Only one of them (MBRI 7) exhibited extracellular protease activity on skim milk agar plates. Based on 16S rDNA sequencing, it belonged to the genus Marinobacter (98 percent sequence similarity, 1201 bp). The cell free extract was used to study effects of temperature and pH on protease activity. The optimum temperature and pH for activity were found to be 40 0C and 7.0 respectively. The crude enzyme was stable at temperature range of 30-80 0C and pH 5.0-9.0. It retained 60 percent activity at 80 0C after 4 h and more than 70 percent activity at 70 0C after 1 h. D value was found to be 342 minutes and 78 minutes for 40 0C and 80 0C respectively. Interestingly the enzyme remained 50 percent active at pH 9.0 after 1 h. Comparison with other proteases from different microbial sources indicated that the neutral protease from the halotolerant marine isolate MBRI 7 is a novel enzyme with high thermostability.