Activity of laccase enzyme extracted from Malva parviflora and its potential for degradation of reactive dyes in aqueous solution

Abstract

The use of enzymes, particularly laccase as a dye-degrading biogenic agent, is a significantly low carbon footprint, bio-inspired approach towards dye wastewater remediation, which not only decomposes and decolorizes the dyes but has also been reported to transmute dyes into less toxic by-products. The work presented herein utilizes both original and purified laccase extracted from Malva parviflora for decomposing pigments that adversely affect ecosystems. Extractions of enzymes from plants were designed by changing one variable at one time and by using response surface methodology (RSM). The optimum enzyme-specific activity of 420 units/mg protein from this flora occurred with extraction for 16.1 min at pH 5.0 with an extraction ratio of 0.17 in 0.42 M sodium acetate buffer. Sephadex G-150 was utilized to filter and purify the enzymes. An ultimate purity of 42% was thus achievable, which constituted a fourfold increase over that of the original extract. The extent to which both natural and purified laccases eliminated textile dyes was assessed under optimal conditions, which were considered to be 180 min at 37 °C. The enzyme extracted from Malva parviflora exhibited high removal efficiency and was able to transmute dyes into less toxic by-products. The extraction process was optimized using response surface methodology, resulting in an optimum enzyme-specific activity. The study found that unpurified enzymes exhibited a greater removal efficiency of dyes compared to purified enzymes. Overall, the findings suggest that laccase enzyme from Malva parviflora could serve as a practical biocatalyst for continuous decolorization of textile dyes with low carbon footprint.