Immobilization ofRhizomucor mieheilipase onto montmorillonite K-10 and polyvinyl alcohol gel

Immobilization of recombinant Trametes versicolor aflatoxin B1-degrading enzyme (TV-AFB1D) with montmorillonite for absorption and in situ degradation of aflatoxin B1

Aflatoxin B1 is a highly carcinogenic and teratogenic substance mainly produced by toxin-producing strains such as Aspergillus flavus and Aspergillus parasitic. The efficient decomposition of aflatoxin is an important means to reduce its harm to humans and livestock. In this study, Trametes versicolor aflatoxin B1-degrading enzyme (TV-AFB1D) was recombinantly expressed in Bacillus subtilis (B. subtilis) 168. MMT-CTAB-AFB1D complex was prepared by the immobilization of TV-AFB1D and montmorillonite (MMT) by cross-linking glutaraldehyde. The results indicated that TV-AFB1D could recombinantly express in engineered B. subtilis 168 with a size of approximately 77 kDa. The immobilization efficiency of MMT-CTAB-AFB1D reached 98.63% when the concentration of glutaraldehyde was 5% (v/v). The relative activity of TV-AFB1D decreased to 72.36% after reusing for 10 times. The content of AFB1 in MMT-CTAB-AFB1D-AFB1 decreased to 1.1 µg/g from the initial 5.6 µg/g after incubation at 50 °C for 6 h. The amount of 80.4% AFB1 in the MMT-CTAB-AFB1D-AFB1 complex was degraded by in situ catalytic degradation. Thus, the strategy of combining adsorption and in situ degradation could effectively reduce the content of AFB1 residue in the MMT-CTAB-AFB1D complex.

Utilization of Clay Materials as Support for Aspergillus japonicus Lipase: An Eco-Friendly Approach

Lipase is an important group of biocatalysts, which combines versatility and specificity, and can catalyze several reactions when applied in a high amount of industrial processes. In this study, the lipase produced by Aspergillus japonicus under submerged cultivation, was immobilized by physical adsorption, using clay supports, namely, diatomite, vermiculite, montmorillonite KSF (MKSF) and kaolinite. Besides, the immobilized and free enzyme was characterized, regarding pH, temperature and kinetic parameters. The most promising clay support was MKSF that presented 69.47% immobilization yield and hydrolytic activity higher than the other conditions studied (270.7 U g−1). The derivative produced with MKSF showed high stability at pH and temperature, keeping 100% of its activity throughout 12 h of incubation in the pH ranges between 4.0 and 9.0 and at a temperature from 30 to 50 °C. In addition, the immobilized lipase on MKSF support showed an improvement in the catalytic performance. The study shows the potential of using clays as support to immobilized lipolytic enzymes by adsorption method, which is a simple and cost-effective process.

Immobilization of Mutant Phosphotriesterase on Fuller’s Earth Enhanced the Stability of the Enzyme

Immobilization is a method for making an enzyme more robust in the environment, especially in terms of its stability and reusability. A mutant phosphotriesterase (YT PTE) isolated from Pseudomonas dimunita has been reported to have high proficiency in hydrolyzing the Sp and Rp-enantiomers of organophosphate chromophoric analogs and therefore has great potential as a decontamination agent and biosensor. This work aims to investigate the feasibility of using Fuller’s earth (FE) as a YT PTE immobilization support and characterize its biochemical features after immobilization. The immobilized YT PTE was found to show improvement in thermal stability with a half-life of 24 h compared to that of the free enzyme, which was only 8 h. The stability of the immobilized YT PTE allowed storage for up to 4 months and reuse for up to 6 times. The immobilized YT PTE showed high tolerance against all tested metal ions, Tween 40 and 80 surfactants and inorganic solvents. These findings showed that the immobilized YT PTE became more robust for use especially with regards to its stability and reusability. These features would enhance the future applicability of this enzyme as a decontamination agent and its use in other suitable industrial applications.