Molybdate-reducing and SDS-degrading Enterobacter sp. Strain Neni-13

Toxicants removal through microorganism’s action is intensely being sought due to economic reasons. The aim of this paper is to isolate a bacterium that is able to reduce molybdenum blue and at the same time can grow on the detergent Sodium Dodecyl Sulfate (SDS). Biochemical analysis resulted in a tentative identification of the bacterium as Enterobacter sp. strain Neni-13. Growth on SDS showed a 100 % removal at 800 mg/L SDS within 12 days. The removal of SDS from media was confirmed through Methylene Blue Active Substances Assay. Molybdenum reduction using sodium molybdate as a substrate was characterized using a microplate assay. The optimum pH and temperature for molybdenum reduction was between 6.0 and 6.5, and at 37 °C, respectively. Glucose was the best electron donor for molybdate reduction. Phosphate and molybdate concentrations of between 2.5 and 5.0 mM and at 15 mM, were optimal for molybdate reduction, respectively. Molybdate reduction was inhibited by the heavy metals mercury, silver, copper and chromium at 2 ppm. The ability of this bacterium to detoxify molybdate and degrade the SDS makes this bacterium an important tool for bioremediation of toxicants in soil.

Isolation and characterization of an acrylamide-degrading Antarctic bacterium

The presence of acrylamide in the environment poses a threat due to its well known neurotoxic, carcinogenic and teratogenic properties. Human activities in various geographical areas are the main anthropogenic source of acrylamide pollution. In this work, an acrylamide-degrading bacterium was isolated from Antarctic soil. The physiological characteristics and optimum growth conditions of the acrylamide-degrading bacteria were investigated. The isolate was tentatively identified as Pseudomonas sp. strain DRYJ7 based on carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny. The results showed that the best carbon sources for growth was glucose and sucrose with no significant difference in terms of cellular growth between the two carbon sources (p>0.05). This was followed by fructose and maltose with fructose giving significantly higher cellular growth compared to maltose (p<0.05). Lactose and citric acid did not support growth. The optimum acrylamide concentration as a nitrogen source for cellular growth was at 500 mgl(-1). At this concentration, bacterial growth showed a 2-day lag phase before degradation took place concomitant with an increase in cellular growth. The isolate exhibited optimum growth in between pH 7.5 and 8.5. The effect of incubation temperature on the growth of this isolate showed an optimum growth at 15 degrees C. The characteristics of this isolate suggest that it would be useful in the bioremediation of acrylamide.

Isolation and characterization of an acrylamide-degrading Bacillus cereus

Several local acrylamide-degrading bacteria have been isolated. One of the isolate that exhibited the highest growth on acrylamide as a nitrogen source was then further characterized. The isolate was tentatively identified as Bacillus cereus strain DRY135 based on carbon utilization profiles using Biolog GP plates and partial 16S rDNA molecular phylogeny. The isolate grew optimally in between the temperatures of 25 and 30 degrees C and within the pH range of 6.8 to 7.0. Glucose, fructose, lactose, maltose, mannitol, citric acid and sucrose supported growth with glucose being the best carbon source. Different concentrations of acrylamide ranging from 100 to 4000 mg l(-1) incorporated into the growth media shows that the highest growth was obtained at acrylamide concentrations of between 500 to 1500 mg l(-1). At 1000 mg l(-1) of acrylamide, degradation was 90% completed after ten days of incubation with concomitant cell growth. The metabolite acrylic acid was detected in the media during degradation. Other amides such as methacrylamide, nicotinamide, acetamide, propionamide and urea supported growth with the highest growth supported by acetamide, propionamide and urea. Strain DRY135, however was not able to assimilate 2-chloroacetamide. The characteristics of this isolate suggest that it would be useful in the bioremediation of acrylamide.