Optimization and production of laccase enzyme by Bacillus cereus isolated from effluent of paint producing industry

Abstract

Paint industry uses different coloured pigment that are known to contain heavy metals including titanium dioxide, iron oxides, aluminium, mica flakes, cadmium, mercury and lead. Laccase enzyme has been reported to have the ability to degrade heavy metals used in different industries. Laccase enzyme is associated with a wide class of enzymes called polyphenol oxidases which are useful in industries such as wine and beverage, baking, textile, printing and tannery and pharmaceutical. Microorganisms produce enzymes such as laccase for bioremediation. This study is aimed at isolating bacteria from waste water of paint industry, screening for potential laccase producing bacteria and production of laccase enzyme. Bacteria were isolated from effluent from paint industry and were screened for laccase enzyme using 0.04% guaiacol. Bacteria with highest enzyme activity were used for optimization studies of temperature, pH, inoculum volume, substrate concentration and copper sulphate concentration. Duncan multiple range test was utilized to separate means after the experiments were conducted in triplicate. Data were analysed with Statistical Package for Social Sciences. Different bacteria were isolated but Bacillus cereus had the highest laccase enzyme activity after primary and secondary screening. Optimization of growth parameters showed that B. cereus had 0.0489 U/mL laccase activity as the highest. Synthesis of laccase enzyme was optimum at 5 days, pH 6.0, 35 °C temperature, 5% inoculum volume, 5 mM guaiacol concentration and 0.3 mM concentration of copper sulphate. This study’s findings demonstrated that bacteria are found in paint industry effluent and these bacteria can produce laccase enzyme which can effectively be employed in bioremediation of soil contaminated by heavy metals present in effluents from paint industry thereby preventing environmental pollution.