Process optimization of polyphenol oxidase immobilization: Isotherm, kinetic, thermodynamic and removal of phenolic compounds

Screening, cloning, immobilization and application prospects of a novel β-glucosidase from the soil metagenome

The soil environment for straw return is a rich and valuable library containing many microorganisms and proteins. In this study, we aimed to screen a high-quality β-glucosidase (BGL) from the soil metagenomic library and to overcome the limitation of the low extraction rate of resveratrol in Polygonum cuspidatum. This includes the construction of a soil metagenomic library, screening of BGL, bioinformatics analysis, cloning, expression, immobilization, enzymatic property analysis, and application for the transformation of polydatin. The results showed that the soil metagenomic library of straw return was successfully constructed, and a novel BGL was screened. The identified 1356 bp long BGL belonged to the glycoside hydrolase 1 (GH1) family and was named Bgl1356. After successful cloning and expression of Bgl1356, it was immobilized using chitosan. The optimum temperature of immobilized Bgl1356 was 50 °C, and the pH was 5. It exhibited good tolerance for various metal ions (CO2+, Ni2+, Cu2+, Mn2+, Na2+, Ca2+, and Ag+) and organic solvents (DMSO, Triton-X-10, and ethanol). Enzymatic kinetics assays showed that Bgl1356 had good affinity for the substrate, and the specific enzyme activity was 234.03 U/mg. The conversion rate of polydatin by immobilized Bgl1356 was 95.70 ± 1.08%, facilitating the production of high amounts of resveratrol. Thus, this paper reports a novel temperature-, organic solvent-, and metal ion-tolerant BGL that has good application prospects in the pharmaceutical industry.

Immobilization of Agaricus bisporus Polyphenol Oxidase 4 on mesoporous silica: Towards mimicking key enzymatic processes in peat soils

HYPOTHESIS

The use of immobilized enzyme-type biocatalysts to mimic specific processes in soil can be considered one of the most promising alternatives to overcome the difficulties behind the structural elucidation of riverine humic-derived iron-complexes. Herein, we propose that the immobilization of the functional mushroom tyrosinase, Agaricus bisporus Polyphenol Oxidase 4 (AbPPO4) on mesoporous SBA-15-type silica could contribute to the study of small aquatic humic ligands such as phenols.

EXPERIMENTS

The silica support was functionalized with amino-groups in order to investigate the impact of surface charge on the tyrosinase loading efficiency as well as on the catalytic performance of adsorbed AbPPO4. The oxidation of various phenols was catalyzed by the AbPPO4-loaded bioconjugates, yielding high levels of conversion and confirming the retention of enzyme activity after immobilization. The structures of the oxidized products were elucidated by integrating chromatographic and spectroscopic techniques. We also evaluated the stability of the immobilized enzyme over a wide range of pH values, temperatures, storage-times and sequential catalytic cycles.

FINDINGS

This is the first report where the latent AbPPO4 is confined within silica mesopores. The improved catalytic performance of the adsorbed AbPPO4 shows the potential use of these silica-based mesoporous biocatalysts for the preparation of a column-type bioreactor for in situ identification of soil samples.

Use of tyrosinase-inorganic salt hybrid nanoflowers and tyrosinase-MOF hybrid composites for elimination of phenolic pollutants from industrial wastewaters

Removal of phenolic pollutants from industrial wastewaters is always an important practical problem. Use of enzymes for dephenolization provides a green solution. In this work, enzymatic methods were developed by employing mushroom tyrosinase immobilized as enzyme-Cu₃(PO₄)₂ hybrid nanoflowers and enzyme-metal organic framework (i.e., ZIF-8 and HKUST-1) hybrid composites, which were shown to be superior to processes mediated by tyrosinase immobilized on other supports in both dephenolization efficiency and reusability. Comparatively, tyrosinase@Cu₃(PO₄)₂ and tyrosinase@HKUST-1 were better than tyrosinase@ZIF-8 in both specific activity and dephenolization efficiency. Typical phenolic pollutants, including 3 monophenols (phenol, p-cresol, p-chlorophenol) and 3 bisphenols (BPA, BPB, BPF), can be completely eliminated within 0.5-4 h. The dephenolization order was discussed based on the enzyme's substrate specificity. The operability and reusability of these hybrid biocomposites were highly improved by entrapping into alginate gels or by incorporating with modified magnetic Fe₃O₄ nanoparticles. Particularly, the magnetic biocatalyst was prepared via a facile one-pot/one-step de novo synthetic strategy, optimized by using response surface methodology (RSM). The as-prepared magnetic tyrosinase@mHKUST-1 retained a high dephenolization efficiency of 81% after 10 cycles and was effective for continuous dephenolization for at least 24 h. These hybrid biocomposites were also successfully applied to treatment of real industrial wastewater from a coke plant.

The evaluation of the performance of rice husk and rice straw as potential matrix to obtain the best lipase immobilized system: creating wealth from wastes

India generates 126.6 and 42 million tons of Rice straw (RS) and Rice husk (RH) annually, respectively. These agro-processing wastes feedstock are dumped in landfills or burnt, releasing toxic gases and particulate matter into the environment. This paper explores the valorization of these wastes feedstock into sustainable, economic products. We compare these wastes as matrices for lipase immobilization. These matrices were characterized, different parameters (pH, temperature, ionic strength, and metal ion cofactors) were checked, and the selected matrix was analyzed for reusability and hydrolysis of vegetable oils. Lipase immobilized Rice straw (LIRS) showed the highest activity with 72.84% protein loading. Field emission scanning electron microscopy (FESEM) demonstrated morphological changes after enzyme immobilization. FTIR showed no new bond formation, and immobilization data was fitted to Freundlich adsorption isotherm (with K = 12.18 mg/g, n_F = 4.5). The highest activity with protein loading, 91.05%, was observed at pH 8, 37 °C temperature, 50 mM ionic strength, and lipase activity doubled in the presence of Mg²⁺ ions. The LIRS retained 75% of its initial activity up to five cycles and efficiently hydrolyzed different oils. The results reflected that the LIRS system performs better and can be used to degrade oily waste.

A Theoretical and Experimental Study for Enzymatic Biodiesel Production from Babassu Oil (Orbignya sp.) Using Eversa Lipase

A theoretical and experimental study was carried out on the biocatalytic production of babassu biodiesel through enzymatic hydroesterification. The complete hydrolysis of babassu oil was carried out using a 1:1 mass solution at 40 °C for 4 h using 0.4% of lipase from Thermomyces lanuginosus (TLL). Then, with the use of Eversa® Transform 2.0 lipase in the esterification step, a statistical design was used, varying the temperature (25–55 °C), the molar ratio between free fatty acids (FFAs) and methanol (1:1 to 1:9), the percentage of biocatalyst (0.1% to 0.9%), and the reaction time (1–5 h) using the Taguchi method. The ideal reaction levels obtained after the statistical treatment were 5 h of reaction at 40 °C at a molar ratio of 1:5 (FFAs/methanol) using 0.9% of the biocatalyst. These optimal conditions were validated by chromatographic analysis; following the EN 14103 standard, the sample showed an ester concentration of 95.76%. A theoretical study was carried out to evaluate the stability of Eversa with FFAs. It was observed in the molecular docking results that the ligands interacted directly with the catalytic site. Through molecular dynamics studies, it was verified that there were no significant conformational changes in the studied complexes. Theoretical and experimental results show the feasibility of this process.

Immobilization of Biomass Materials for Removal of Refractory Organic Pollutants from Wastewater

In the field of environmental science and engineering, microorganisms, enzymes and algae are promising biomass materials that can effectively degrade pollutants. However, problems such as poor environmental adaptability, recycling difficulties, and secondary pollution exist in the practical application of non-immobilized biomass materials. Biomass immobilization is a novel environmental remediation technology that can effectively solve these problems. Compared with non-immobilized biomass, immobilized biomass materials have the advantages of reusability and stability in terms of pH, temperature, handling, and storage. Many researchers have studied immobilization technology (i.e., methods, carriers, and biomass types) and its applications for removing refractory organic pollutants. Based on this, this paper reviews biomass immobilization technology, outlines the mechanisms and factors affecting the removal of refractory organic pollutants, and introduces the application of immobilized biomass materials as fillers for reactors in water purification. This review provides some practical references for the preparation and application of immobilized biomass materials and promotes further research and development to expand the application range of this material for water purification.

Advances in the application of immobilized enzyme for the remediation of hazardous pollutant: A review

Nowadays, ecofriendly, low-cost, and sustainable alternatives techniques have been focused on the effective removal of hazardous pollutants from the water streams. In this context, enzyme immobilization seems to be of specific interest to several researchers to develop novel, effective, greener, and hybrid strategies for the removal of toxic contaminants. Immobilization is a biotechnological tool, anchoring the enzymes on support material to enhance the stability and retain the structural conformation of enzymes for catalysis. Recyclability and reusability are the main merits of immobilized enzymes over free enzymes. Studies showed that immobilized enzyme laccase can be used up to 7 cycles with 66% efficiency, peroxidase can be recycled to 2 cycles with 50% efficiency, and also cellulase to 3 cycles with 91% efficiency. In this review, basic concepts of immobilization, different immobilization techniques, and carriers used for immobilization are summarized. In addition to that, the potential of immobilized enzymes as the bioremediation agents for the effective degradation of pollutants from the contaminated zone and the impact of different operating parameters are summarized in-depth. Further, this review provides future trends and challenges that have to be solved shortly for enhancing the potential of immobilized systems for large-scale industrial wastewater treatment.