Acetamide hydrolyzing activity of Bacillus megaterium F-8 with bioremediation potential: optimization of production and reaction conditions.

Bacillus megaterium F-8 exhibited an intracellular acetamide hydrolyzing activity (AHA) when cultivated in modified nutrient broth with 3% tryptone, 1.5% yeast extract, and 0.5% sodium chloride, at pH 7.2, 45 °C for 24 h. Maximum AHA was recorded in the culture containing 0.1 M of sodium phosphate buffer, (pH 7.5) at 45 °C for 20 min with 0.2 % of acetonitrile and resting cells of B. megaterium F-8 equivalent to 0.2 ml culture broth. This activity was stable up to 55 °C and was completely inactivated at or above 60 °C. Maximum acyl transferase activity (ATA) was recorded in the reaction medium containing 0.1 M of potassium phosphate buffer, (pH 8.0) at 55 °C for 5 min with 0.85 mM of acetamide as acyl donor and hydroxylamine hydrochloride as acyl acceptor and resting cells of B. megaterium F-8 equivalent to 0.94 mg cells (dry weight basis). This activity was stable up to 60 °C and a rapid decline in enzyme activity was recorded above it. Under the optimized conditions, this organism hydrolyzed various nitriles and amides such as propionitrile, propionamide, caprolactam, acetamide, and acrylamide to corresponding acids. Acyl group transfer capability of this organism was used for the production of acetohydroxamic acid. ATA of B. megaterium F-8 showed broad substrate specificity such as for acetamide followed by propionamide, acrylamide, and lactamide. This amide hydrolyzing and amidotransferase activity of B. megaterium F-8 has potential applications in enzymatic synthesis of hydroxamic acids and bioremediation of nitriles and amides contaminated soil and water system.

Use of Salmonella/microsome reversion bioassay for monitoring industrial wastewater treatment plants in Rajasthan, India.

Salmonella/microsome reversion assay was used as a biological parameter for monitoring the toxicity of common effluent treatment plant (CETP), Mandia road industrial area, Pali catering to textile industrial areas in Pali, Rajasthan. The influent and effluent water of CETP, surface water (Bandi river) and underground water were tested using Ames bioassay. The results showed presence of mutagens in surface water of Bandi river and the underground water in Pali. Further, comparison of mutagenicity of CETP influent and effluent water revealed that the treatment method employed at this plant has failed to remove mutagenic substances present in Pali textile wastewater. The study also showed that Ames assay is an important tool in genotoxic studies because of its simplicity, sensitivity to genetic damage, speed, low cost of experimentation and small amount of sample required. Further Ames assay, as seen from the results of this study, can be used as a monitoring tool for not only CETPs but also for other water resources. The outcomes of the Ames assay demonstrated its performance as a sensitive, cost-effective and relatively rapid screening tool to assess the genotoxic potential of complex environmental samples.

Mutagenicity evaluation of industrial sludge from common effluent treatment plant.

Sludge from common effluent treatment plant (CETP) receiving effluents from textile industries at Mandia Road, Pali, was analyzed to assess the level of mutagenicity. Mutagenicity assay using Salmonella typhimurium tester strains TA 98 and TA 100 gave positive results, thus suggesting presence of genotoxic contaminants in the samples investigated. Further, mutagenic activity of chemical sludge was found to be lesser than that of biological sludge. This result is very surprising and unexpected as it is indicating that some mutagenic compounds are either being formed or certain promutagenic compounds are being converted into stable mutagenic metabolites during the biological treatment of the wastewater effluents. There have been no previous reports giving similar or contrary results. Most of the previous studies have reported effects of single combined sludge.