Removal of Microcystin-Lr using Cellular Extracts of Bacillus Cereus

Abstract

Microcystin –LR (MC-LR) is considered to be the most dominant type of cyanobacterial toxins present in water bodies. The present study focuses on using cellular extracts of Bacillus cereus in removal of MC-LR in water. Bacterial cell extracts were prepared using overnight grown fresh cultures of B. cereus which was previously recorded as a potent MC-LR degrading bacterium. Bacterial cell disruption was performed by bead beating on a micro-mini bead beater. Cell debris was removed by centrifugation at 13000 rpm, 20 min. Subsequently, a series of concentrations of cellular extract (100%, 75%, 50% and 25%) was prepared. These cell extracts were separately incubated at 280C with 100µg ml-1 of MC-LR for a period of 4 days. 1ml aliquots were removed at 24 hour intervals for four days and frozen at (-20) 0C. Then the frozen samples were freeze-dried and subjected to Photo diode array- High Performance Liquid Chromatography (PDA-HPLC) analysis to detect the remaining MC-LR concentrations of the samples. At the end of fourth day, 81.1 µgml-1 of MC-LR was removed when 100% of cell extract was used. When 75 % of cell extract was used, 77.6 µgml-1 of MC-LR removal was evident at the end of fourth day, whereas when 50 % and 25% of cell extract were used only 40.7 µgml-1 and 25.7 µgml-1 of MC-LR removal was detected respectively. The results of the present study indicate that bacterial cell extracts of B. cereus has the ability to remove MC-LR by an enzyme mediated mechanism.