Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Improvement of Ficin-Based Inhibitive Enzyme Assay for Mercury Using Response Surface Methodology and Its Application for Near Real-Time Monitoring of Mercury in Marine Waters

Version 1 : Received: 29 August 2020 / Approved: 31 August 2020 / Online: 31 August 2020 (03:53:15 CEST)

How to cite: Uba, G.; Manogaran, M.; Gunasekaran, B.; Halmi, M.I.E.; Shukor, M.Y.A. Improvement of Ficin-Based Inhibitive Enzyme Assay for Mercury Using Response Surface Methodology and Its Application for Near Real-Time Monitoring of Mercury in Marine Waters. Preprints 2020, 2020080689 (doi: 10.20944/preprints202008.0689.v1). Uba, G.; Manogaran, M.; Gunasekaran, B.; Halmi, M.I.E.; Shukor, M.Y.A. Improvement of Ficin-Based Inhibitive Enzyme Assay for Mercury Using Response Surface Methodology and Its Application for Near Real-Time Monitoring of Mercury in Marine Waters. Preprints 2020, 2020080689 (doi: 10.20944/preprints202008.0689.v1).

Abstract

Heavy metals pollution in the Straits of Malacca warrants the development of rapid, simple and sensitive assays. Enzyme-based assays are excellent preliminary screening tool with near real-time potential. The heavy-metal assay based on the protease ficin was optimized for mercury detection using Response Surface Methodology. The inhibitive assay is based on ficin action on the substrate casein and residual casein is determined using the Coomassie dye-binding assay. Heavy metals strongly inhibit the hydrolysis. A Central Composite Design (CCD) was utilized to optimize detection. The results show a marked improvement for the concentration causing 50% inhibition (IC50) for mercury, silver and copper. Compared to One-factor-at-a-time (OFAT) optimization, RSM gave an improvement of IC50 from 0.060 (95% CI, 0.0300.080) to 0.017 (95% CI, 0.0160.019), from 0.098 (95% CI, 0.0770.127) to 0.028 (95% CI, 0.0220.037) and from 0.040 (95% CI, 0.035.045) to 0.023 (95% CI, 0.0200.027), for mercury, silver and copper, respectively. A near real-time monitoring of mercury concentration in the Straits of Malacca at one location in Port Klang was carried out over a 4-h interval for a total of 24 h and validated by instrumental analysis with the result revealing an absence of mercury pollution in the sampling site.

Subject Areas

Inhibitive assay; mercury; ficin; RSM; near real-time

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