Evaluation of a Trametes pubescens laccase concentrated extract on allura red AC decolorization without the addition of synthetic mediators

In silico and in vitro assays suggests Congo red dye degradation by a Lentinus sp. laccase enzyme

Laccase is a superfamily of ligninolytic enzymes known to degrade a wide variety of xenobiotics, including synthetic dyes. Congo Red (CR) has a diazo dye function, carcinogenic and mutagenic potential, and is currently applied in clinical analysis. The objective of this work was to produce and characterize the crude extract of Lentinus sp. in semi-solid fermentation (FSS) and perform in vitro and in silico studies to assess the potential of the crude extract to discolor the CR dye. Laccase activity was determined using ABTS as substrate and characterized. The in vitro discoloration was carried out using experimental design 22 at room temperature and monitored at 340 nm for 24h. Molecular docking and molecular dynamics simulations were performed between laccase and CR. The maximum laccase activity production was 29.63 U L-1 with six days of FSS. The optimal temperature and pH were 50 °C and 3.0, respectively. Discoloration of the CR dye was obtained only in tests containing CuSO4. Laccase formed stable complexes with the dye, presenting negative binding energy values ranging from -70.94 to -63.16 kcal mol-1 and the occurrence of seven hydrogen bonds. Molecular dynamics results showed the stability of the system (RMSD ranging from 1.0 to 2.5 Ä) and protein-ligand interaction along simulation. RMSF values pointed residues at the end of chains A (residues 300 to 305, 480 to 500) and B (residues 650 to 655 and 950 to 1000) as the most flexible regions of the laccase. This study highlighted the enzymatic action in the bioremediation of CR in vitro in agreement with the in silico simulations that demonstrate the enzyme potential.Communicated by Ramaswamy H. Sarma.

Co-immobilization of glucose oxidase and catalase in porous magnetic chitosan microspheres for production of sodium gluconate

In the process of immobilizing the enzyme, the overflow of enzyme and the decrease of enzyme activity are very serious. In order to improve the stable binding between enzyme and carrier, a kind of porous magnetic chitosan microsphere with appropriate pore size was successfully prepared by adjusting the size of pore-forming agent in this paper. The rough porous structure is favorable for the adsorption of enzyme and the catalytic action of enzyme on substrate. The results showed that when the pore size of the microspheres was at 790.15 ± 250.91 nm, the protein loading and enzyme activity of GOD could be increased effectively, which could reach 58.28 ± 2.64 mg/g and 16.93 ± 0.14 U, respectively. The co-immobilization of CAT and GOD eliminated the harmful by-product H2O2 in time and effectively solved the problem of continuous deactivation of GOD in the reaction process. When the mass ratio of PMCSM/GOD/CAT was 100/6.02/10.96 (mg/mg/mg), the relative enzyme activity of GOD reached the highest (133.32 ± 0.68%). The thermal stability and pH stability of the enzyme were greatly improved after co-immobilization. The relative enzyme activity of PMCSM@GOD@CAT was 57.27 ± 3.04% at 60 °C, while that of free GOD was only 28.76 ± 4.10%. The relative enzyme activity of PMCSM@GOD@CAT was above 63% at pH 5–10, while the relative enzyme activity of free GOD was only 4.98 ± 0.72% at pH 10. The yield of sodium gluconate from 50 mL 250 mg/mL glucose catalyzed by PMCSM@GOD@CAT loading 60.2 mg GOD was 96.19 ± 0.79% at pH 6.0 and 30 °C, and the reaction lasted 6 h. The relative enzyme activity of PMCSM@GOD@CAT remained 69.77 ± 0.78% after repeated use for 10 times. After 30 days of storage, PMCSM@GOD@CAT maintained its initial activity of 76.52 ± 1.41%. The immobilized process studied in this paper provides a theoretical basis for the production of sodium gluconate by double enzyme directly catalyzing and lays a certain foundation for the application of immobilized enzyme in the future chemical industry and food industry.

Magnetic Metal Organic Framework Immobilized Laccase for Wastewater Decolorization

The laccase enzyme was successfully immobilized over a magnetic amino-functionalized metal–organic framework Fe3O4-NH2@MIL-101(Cr). Different techniques were used for the characterization of the synthesized materials. The Fe3O4-NH2@MIL-101(Cr) laccase showed excellent resistance to high temperatures and low pH levels with a high immobilization capacity and large activity recovery, due to the combination of covalent binding and adsorption advantages. The long-term storage of immobilized laccase for 28 days indicated a retention of 88% of its initial activity, due to the high stability of the immobilized system. Furthermore, a residual activity of 49% was observed at 85 °C. The immobilized laccase was effectively used for the biodegradation of Reactive Black 5 (RB) and Alizarin Red S (AR) dyes in water. The factors affecting the RB and AR degradation using the immobilized laccase (dye concentration, temperature and pH) were investigated to determine the optimum treatment conditions. The optimum conditions for dye removal were a 5 mg/L dye concentration, temperature of 25 °C, and a pH of 4. At the optimum conditions, the biodegradation and sorption-synergistic mechanism of the Fe3O4-NH2@MIL-101(Cr) laccase system caused the total removal of AR and 81% of the RB. Interestingly, the reusability study of this immobilized enzyme up to five cycles indicated the ability to reuse it several times for water treatment.