Aim : The cholinesterase (ChE) based inhibition studies from fish were investigated and presented here emerged to be one of the great potential biomarkers for heavy metals monitoring. Methodology : In this study, the capability of ChE extracted from the kidney of Lates calcarifer was assessed for of metal. ChE was purified through ammonium sulphate precipitation and ion exchange chromatography. Results : The purified enzyme gave 12 fold purification with the recovery of 12.17% with specific activity of 2.889 U mg(-1). The Michaelis-Menten constant (K-m) and V-max value obtained was 0.1426 mM and 0.0217 mu mol min(-1)mg(-1), respectively. The enzyme has the ability to hydrolyse acetylthiocholine iodide (ATC) at a faster rate compared to other two synthetic substrates, propionylthiocholine iodide (PTC) and butyrylthiocholine iodide (BTC). ChE gave highest activity at 20-30 degrees C in Tris-HCI buffer pH 8.0. The results showed that cholinesterase from L. calcarifer kidney was very sensitive to sensitive to copper and lead after being tested argentum, arsenic, cadmium, chromium, copper, cobalt, mercury, nickel, lead and zinc. Interpretation : The effect of heavy metals studied on the activity of ChE differed from each other. The result of the study can be used as a tool for further developing a biomarker for the detection of heavy metals in aquatic ecosystems. In addition, the information can also be used for designing a kit, that would give a rapid and accurate result.

The purpose of this study was to investigate the ability of Acinetobacter sp. strain AQ5NOL 1 immobilised in gellan gum beads to degrade phenol in the presence of heavy metals. Sewn different heavy metals, namely, As5+, Cu2+ Cd2+, Ni2+, Cr6+, Ph2+, and He at 1 ppm were tested. Results of the study showed that degradation of phenol by free cells was inhibited by Hg2+, Cu6+ and Cr6+ after 48 hours of incubation by 97.91 %, 77.58 % and 75.26 %, respectively. Only Hg2+ and Cr6+ inhibited phenol degradation by immobilised Acinetobacter cells in 18 hours by 67.55 % and 53.19 %. Phenol degradation by immobilised cells was affected when Cr and Hg2+ concentrations exceeded 0.5 and 0.1 ppm, respectively. However, inhibitory effects of heavy metals can be overcome by prolonging the incubation time for immobilised Acinetobacter sp. strain AQ5NOL 1 from 18 hours to 24 and 30 hours for Cr6+ (46.80 %) and Hg2+ (21.40 %), respectively.