Application of response surface methodology to study the removal of estrogens in a laccase-mediated continuous membrane reactor

Persistence and impact of steroidal estrogens on the environment and their laccase-assisted removal

Steroidal estrogens are widespread water contaminants with potential carcinogenic and endocrine-disrupting activities. The World Health Organization has listed estrogens as group 1 carcinogens. These contaminants are of substantial concern because of potential threats to human health, and aquatic organisms on long-term exposure. A range of methods, including oxidation, adsorption, electrochemical, and irradiation techniques have been employed for their remediation from aqueous systems. However, inadequate removal, toxic sludge generation, high operating costs, and the requisite for skilled operating and maintenance personnel commercially hampered the application of many methods. An interesting alternative treatment approach based on the use of oxidoreductases, particularly laccases, has recently gained amicability for the biotransformation of emerging pollutants. The use of immobilized enzymes is more cost-effective from an industrial perspective due to improved catalytic stability, reusability, reduction of product inhibition, and easier product separation. This review provides comprehensive knowledge on the use of laccases in the biodegradation of steroidal estrogens, including estrone, 17β-estradiol, and 17α-ethinylestradiol with endocrine-disrupting potency from the environment. After an overview of estrogens and catalytic properties of laccase, the use of free, as well as immobilized laccases with a particular emphasis on estrogens removal by laccase-based fed-batch, packed bed bioreactors, and membrane reactors, is discussed. A comparison of existing treatment technologies with enzyme technology for the removal of estrogens from different environmental matrices is made. Lastly, along with concluding remarks, future research direction aimed at bridging knowledge gaps for estrogenic compounds removal are also proposed in this very important research area.

Bacterial laccases: promising biological green tools for industrial applications

Multicopper oxidases (MCOs) are a pervasive family of enzymes that oxidize a wide range of phenolic and nonphenolic aromatic substrates, concomitantly with the reduction of dioxygen to water. MCOs are usually divided into two functional classes: metalloxidases and laccases. Given their broad substrate specificity and eco-friendliness (molecular oxygen from air as is used as the final electron acceptor and they only release water as byproduct), laccases are regarded as promising biological green tools for an array of applications. Among these laccases, those of bacterial origin have attracted research attention because of their notable advantages, including broad substrate spectrum, wide pH range, high thermostability, and tolerance to alkaline environments. This review aims to summarize the significant research efforts on the properties, mechanisms and structures, laccase-mediator systems, genetic engineering, immobilization, and biotechnological applications of the bacteria-source laccases and laccase-like enzymes, which principally include Bacillus laccases, actinomycetic laccases and some other species of bacterial laccases. In addition, these enzymes may offer tremendous potential for environmental and industrial applications.

Cupuaçu (Theobroma grandiflorum) residue and its potential application in the bioremediation of 17-Α-ethinylestradiol as a Pycnoporus sanguineus laccase inducer

Bioremediation is a strategy to mitigate environmental impacts of hazardous pollutants from anthropogenic sources. Natural byproducts, including agroindustrial wastes (AW) can be used to induce enzyme biosynthesis, leading up to enhancement of pollutants degradation process. Therefore, this study aimed to evaluate the use of cupuaçu, Theobroma grandiflorum AW as Pycnoporus sanguineus Laccase (Lac) inducer in order to promote 17-α-ethinylestradiol (EE2) bioremediation. The macro and micro-nutrients levels of cupuaçu AWs were evaluated in order to establish further correlations with enzymatic biosynthesis induction. The fungus was cultivated for 7 days in temperature of 28 ± 2 °C and agitation of 150 rpm. For bioremediation, Lac enzymatic extract was added to EE2 solution (10 µg mL^-1) and the percentage of removal was evaluated by HPLC after 1-24 hr of reaction. At optimized conditions, the enzyme extract production was remarkably enhanced by adding only 1% (w/v) of cupuaçu AW. Lac activity reached 1642 U mL^-1 on the 6th day of culture, which was higher than positive control (511 U mL^-1). 86% of EE2 removal was reached after 4 hr, and after 8 hr of reaction, 96.5% was removed. Analysis by direct infusion in MS-ESI-TOF exhibited intermediary compounds formed by radical hydroxilation.

Biotransformation of Endocrine-Disrupting Compounds in Groundwater: Bisphenol A, Nonylphenol, Ethynylestradiol and Triclosan by a Laccase Cocktail from Pycnoporus sanguineus CS43

The biodegradation of organic compounds present in water at trace concentration has become a critical environmental problem. In particular, enzymatic oxidation by fungal laccases offers a promising alternative for efficient and sustainable removal of organic pollutants in water. In this work, the biocatalytic ability of laccases from the Pycnoporus sanguineus CS43 fungus was evaluated. A filtered culture supernatant (laccase cocktail) evidenced an enhanced biotransformation capability to remove common endocrine-disruptor compounds (EDCs), such as bisphenol A, 4-nonylphenol, 17-α-ethynylestradiol and triclosan. A biodegradation of around 89-100 % was achieved for all EDCs using synthetic samples (10 mg L^-1) and after the enzymatic treatment with 100 U L^-1 (50.3 U mg ^-1). The biodegradation rates obtained were fitted to a first order reaction. Furthermore, enzymatic biocatalytic activity was also evaluated in groundwater samples coming from northwestern Mexico, reaching biotransformation percentages between 55 and 93 % for all tested compounds. As far as we know this is the first study on real groundwater samples in which the enzymatic degradation of target EDCs by a laccase cocktail from any strain of Pycnoporus sanguineus was evaluated. In comparison with purified laccases, the use of cocktail offers operational advantages since additional purification steps can be avoided.

Laccases to take on the challenge of emerging organic contaminants in wastewater

The removal of emerging organic contaminants from municipal wastewater poses a major challenge unsatisfactorily addressed by present wastewater treatment processes. Enzyme-catalyzed transformation of emerging organic contaminants (EOC) has been proposed as a possible solution to this major environmental issue more than a decade ago. Especially, laccases gained interest in this context in recent years due to their broad substrate range and since they only need molecular oxygen as a cosubstrate. In order to ensure the stability of the enzymes and allow their retention and reuse, either immobilization or insolubilization of the biocatalysts seems to be the prerequisite for continuous wastewater treatment applications. The present review summarizes the research conducted on EOC transformation with laccases and presents an overview of the possible immobilization techniques. The goal is to assess the state of the art and identify the next necessary steps that have to be undertaken in order to implement laccases as a tertiary wastewater treatment process in sewage treatment plants.