Facile One-Pot Immobilization of a Novel Thermostable Carboxylesterase from Geobacillus uzenensis for Continuous Pesticide Degradation in a Packed-Bed Column Reactor

Reusable carboxylesterase immobilized in ZIF for efficient degradation of chlorpyrifos in enviromental water

The past few decades have witnessed biodegradation of pesticides as a significant method in remediation of the environment for its specificity, efficiency and biocompatibility. However, the tolerability and recyclability of the enzymes in pesticide degradation and the development of enzymes that biodegrad pesticides are still urgent problems to be solved so far. Herein, a novel hyper-thermostable and chlorpyrifos-hydrolyzing carboxylesterase EstC was immobilized by biomineralization using zeolitic imidazolate framework (ZIF), one of the metal-organic frameworks (MOFs) with highly diverse structure and porosity. Compared with free enzyme, EstC@ZIF with a cruciate flower-like morphology presented scarcely variation in catalytic efficiency and generally improved the tolerance to organic solvents or detergents. Furthermore, there was scarcely decrease in the catalytic efficiency of EstC@ZIF and it also showed good reusability with about 50% residual activity after 12 continuous uses. Notably, EstC@ZIF could be used in actual water environment with an excellent value of degradation rate of 90.27% in 120 min, and the degradation efficiency remained about 50% after 9 repetitions. The present strategy of immobilizing carboxylesterase to treat pesticide-contaminated water broadens the method of immobilized enzymes on MOFs, and envisions its recyclable applicability in globe environmental remediation.

Immobilization of Hyperthermostable Carboxylesterase EstD9 from Anoxybacillus geothermalis D9 onto Polymer Material and Its Physicochemical Properties

Carboxylesterase has much to offer in the context of environmentally friendly and sustainable alternatives. However, due to the unstable properties of the enzyme in its free state, its application is severely limited. The present study aimed to immobilize hyperthermostable carboxylesterase from Anoxybacillus geothermalis D9 with improved stability and reusability. In this study, Seplite LX120 was chosen as the matrix for immobilizing EstD9 by adsorption. Fourier-transform infrared (FT-IR) spectroscopy verified the binding of EstD9 to the support. According to SEM imaging, the support surface was densely covered with the enzyme, indicating successful enzyme immobilization. BET analysis of the adsorption isotherm revealed reduction of the total surface area and pore volume of the Seplite LX120 after immobilization. The immobilized EstD9 showed broad thermal stability (10-100 °C) and pH tolerance (pH 6-9), with optimal temperature and pH of 80 °C and pH 7, respectively. Additionally, the immobilized EstD9 demonstrated improved stability towards a variety of 25% (v/v) organic solvents, with acetonitrile exhibiting the highest relative activity (281.04%). The bound enzyme exhibited better storage stability than the free enzyme, with more than 70% of residual activity being maintained over 11 weeks. Through immobilization, EstD9 can be reused for up to seven cycles. This study demonstrates the improvement of the operational stability and properties of the immobilized enzyme for better practical applications.

Green remediation potential of immobilized oxidoreductases to treat halo-organic pollutants persist in wastewater and soil matrices - A way forward

The alarming presence of hazardous halo-organic pollutants in wastewater and soils generated by industrial growth, pharmaceutical and agricultural activities is a major environmental concern that has drawn the attention of scientists. Unfortunately, the application of conventional technologies within hazardous materials remediation processes has radically failed due to their high cost and ineffectiveness. Consequently, the design of innovative and sustainable techniques to remove halo-organic contaminants from wastewater and soils is crucial. Altogether, these aspects have led to the search for safe and efficient alternatives for the treatment of contaminated matrices. In fact, over the last decades, the efficacy of immobilized oxidoreductases has been explored to achieve the removal of halo-organic pollutants from diverse tainted media. Several reports have indicated that these enzymatic constructs possess unique properties, such as high removal rates, improved stability, and excellent reusability, making them promising candidates for green remediation processes. Hence, in this current review, we present an insight of green remediation approaches based on the use of immobilized constructs of phenoloxidases (e.g., laccase and tyrosinase) and peroxidases (e.g., horseradish peroxidase, chloroperoxidase, and manganese peroxidase) for sustainable decontamination of wastewater and soil matrices from halo-organic pollutants, including 2,4-dichlorophenol, 4-chlorophenol, diclofenac, 2-chlorophenol, 2,4,6-trichlorophenol, among others.

Immobilized GDEst-95, GDEst-lip and GD-95RM lipolytic enzymes for continuous flow hydrolysis and transesterification reactions

In this study lipolytic biocatalysts GD-95RM, GDEst-95 and GDEst-lip were immobilized by encapsulation in calcium alginate beads_. All three immobilized biocatalysts demonstrated significantly increased thermal stability at 60-70 °C temperatures and the activity of GD-95RM lipase increased by 50% at 70-80 °C following the immobilization. Moreover, encapsulated GDEst-95 esterase retained higher than 50% lipolytic activity after 3 months of incubation with butanol (25%) and ethanol (50%); GDEst-lip enzyme possessed 50% activity after 2 months of treatment with ethanol (25%) and methanol (25%); and GD-95RM lipase displayed higher that 50% activity after two-week incubation with methanol (50%). All three immobilized enzymes displayed long-term storage capability (>50% activity) at least until 3 months at 4 °C. It was also detected that immobilized GD-95RM and GDEst-lip can perform flow hydrolysis of both avocado oil and p-NP dodecanoate in prototype packed-bed column reactor. The analysis of continuous transesterification of avocado or sunflower oil with ethanol or methanol as substrates confirmed that encapsulated GD-95RM and GDEst-lip enzymes is a useful approach to produce fatty acid alkyl esters.