MAYA GEORGE, CLITTIN BABY, JISS VINCENT AND A.A. MOHAMED HATHA
Abstract
The bioremediation of heavy metals using microorganisms has received a great deal of attention in recent years, not only as a scientific novelty but also for its potential application in industry. In the present investigation tolerance of various Gram-positive and Gram-negative bacterial strains isolated from Vembanadu lake, against heavy metals such as chromium, copper, nickel and cadmium were tested. Gram positive bacterial isolates included Bacillus subtilis, Bacillus sphaericus, Bacillus polymyxa, Thermobacillus, and Alicyclobacillus and Gram negative isolates included Enterobacter aerogens and Pseudomonas sp. Heavy metal tolerance and minimum inhibitory concentration (MIC) of the above bacteria were tested using nutrient broth having various concentrations of heavy metals. MIC and tolerance range of test bacterial isolates to different heavy metals showed variations. Thermobacillus showed high tolerance towards cadmium (up to 12.5mM) which could be used in cadmium removal from polluted environments. This strain was further evaluated for its ability to grow in 12.5mM of cadmium solution having different pH (4, 5, 6, 7, 8 and 9), which revealed maximum growth at pH 5 and minimum growth at pH 9.