Valorization of Some Solid Environmental Wastes for Treating Liquid Waste: The Closed Switch

The prospect of enzymatic treatment of pollutants has gradually been receiving growing attention in contemporary times due to the their environmental friendliness and production economic feasibility. Laccase, a multi-copper oxidase has heightened its appeal towards environmental and biotechnological applications due to its broad substrate specificity and its requirement of atmospheric molecular oxygen as a co-substrate and the discharge of water as the byproduct. Hence, this present study was designed to evaluate the biotechnological potentials of laccases produced by some bacteria species from some aquatic milieu of the Eastern Cape Province, South Africa. Optimization of laccase production in a submerged fermentation was by traditional and statistical methods, where the fermentative production of laccase from lignocellulosic agroindustrial residues was evaluated. Laccase secretions produced from statistical optimization exhibited enhanced polyextremotolerant capacities. They were active at a broad range of temperature (0-90°C); with optima at 70°C (Hb9c) and 60°C (Ie1c), pH (3-11); with optima at pH 6 (Ie1c) and pH 8 (Hb9c), respectively, and were equally thermo- and pH-stable. Their activities were either improved or left unabated by high concentrations of cations, detergents, and chloride. In addition, catalytic activities of some secretions increased when they were pre-incubated with 2 – 20% of fluoride, a potent inhibitor. Consequently, a molecular perspective depicted the isolates to have multiple homologous laccase encoding genes. The laccases were remarkable in the decolourization of synthetic dyes. Ultimately, the application of free laccases in denim bleaching, individually or with a blend of a mediator, ABTS, showed that denim colors could be bleached without the need for chemical bleaching agents. The results obtained suggest the bacterial laccases produced from lignocellulosic wastes may serve as potent degraders of phenolic pollutants in water and, may also contribute to the bioeconomy and promote greener techniques for industrial applications.