A new biocomposite based on microbial autocrine laccase-rice straw: Preparation, characterization and application

Abstract

The immobilization of laccase on crop residues is a promising way to treat water containing bisphenol A (BPA), but the high cost of commercially available solutions of this enzyme indicates a need for research into feasible cost-effective alternatives. Here, a new biocomposite was developed based on a microbial autocrine laccase process, where rice straw served as the sole carbon source and as a carrier mixed with Comamonas testosteroni FJ17 ( C. testosteroni FJ17). A laccase-rice straw biocomposite (RS-Lac) was prepared via a one-step synthesis and subsequently evaluated for the removal of BPA. A response surface methodology was used to optimize the synthesis of RS-Lac, where the subsequent removal efficiency of BPA (500 μg L −1 ) by RS-Lac biocomposite increased from 46.1 (unoptimized) to 57.0% (optimized). The molecular weight (Mw) of laccase was identified by SDS-PAGE to be 34 kDa. SEM, CLSM , FTIR, and XRD results confirmed laccase secreted by C. testosteroni FJ17 was coated with polysaccharides , and these were successfully immobilized on rice straw. The specific surface area of RS-Lac increased from 2.79 to 5.37 m 2 g −1 following synthesis optimization, and zeta potential analyzer indicated that it carried a strong negative charge. In addition, RS-Lac was also used to successfully remove estrone (E1), 17β-estradiol (E2), Cu(II), Sb(Ⅲ), As(Ⅲ), and As(Ⅴ) to varying degrees, with removal efficiencies of 68.7%, 66.4%, 77.5%, 84.0%, 83.7%, and 91.6%, respectively. This broad versatility indicated that RS-Lac has great potential as a low-cost biocomposite for treating wastewater. • A rice straw-i autocrine laccase biocomposite was prepared in one-step. • Various characterizations confirmed that crude laccase immobilized on rice straw. • The rice straw was coated with polysaccharides and immobilized laccase. • Degradation of bisphenol A (57%) to small molecular fragments in solution. • Heavy metal ions (>77.5%) and estrogen (>66.4%) were removed.