Covalent immobilization of benzoylformate decarboxylase from Pseudomonas putida on magnetic epoxy support and its carboligation reactivity

Optimized enantioselective (S)-2-hydroxypropiophenone synthesis by free- and encapsulated-resting cells of Pseudomonas putida

BACKGROUND

Aromatic α-hydroxy ketones, such as S-2-hydroxypropiophenone (2-HPP), are highly valuable chiral building blocks useful for the synthesis of various pharmaceuticals and natural products. In the present study, enantioselective synthesis of 2-HPP was investigated by free and immobilized whole cells of Pseudomonas putida ATCC 12633 starting from readily-available aldehyde substrates. Whole resting cells of P. putida, previously grown in a culture medium containing ammonium mandelate, are a source of native benzoylformate decarboxylase (BFD) activity. BFD produced by induced P. putida resting cells is a highly active biocatalyst without any further treatment in comparison with partially purified enzyme preparations. These cells can convert benzaldehyde and acetaldehyde into the acyloin compound 2-HPP by BFD-catalyzed enantioselective cross-coupling reaction.

RESULTS

The reaction was carried out in the presence of exogenous benzaldehyde (20 mM) and acetaldehyde (600 mM) as substrates in 6 mL of 200 mM phosphate buffer (pH 7) for 3 h. The optimal biomass concentration was assessed to be 0.006 g dry cell weight (DCW) mL^- 1. 2-HPP titer, yield and productivity using the free cells were 1.2 g L^- 1, 0.56 g 2-HPP/g benzaldehyde (0.4 mol 2-HPP/mol benzaldehyde), 0.067 g 2-HPP g^- 1 DCW h^- 1, respectively, under optimized biotransformation conditions (30 °C, 200 rpm). Calcium alginate (CA)-polyvinyl alcohol (PVA)-boric acid (BA)-beads were used for cell entrapment. Encapsulated whole-cells were successfully employed in four consecutive cycles for 2-HPP production under aerobic conditions without any noticeable beads degradation. Moreover, there was no production of benzyl alcohol as an unwanted by-product.

CONCLUSIONS

Bioconversion by whole P. putida resting cells is an efficient strategy for the production of 2-HPP and other α-hydroxyketones.

Covalent Immobilization of Candida rugosa Lipase on Epichlorohydrin-Coated Magnetite Nanoparticles: Enantioselective Hydrolysis Studies of Some Racemic Esters and HPLC Analysis

In this study, a new biocatalyst was prepared by immobilizing Candida rugosa lipase epichlorohydrin-functionalized onto the surface of the nanoparticles. Magnetite nanoparticles were obtained by chemical co-precipitation method of Fe²⁺ and Fe³⁺, and then the prepared uncoated and coated nanoparticles were characterized by XRD, FT-IR and TGA. Lipase was covalently attached to activated nanoparticles. The catalytic properties of free and immobilized lipases were determined. It was found that the optimum temperature for free and immobilized lipases was 30 °C and 35 °C, respectively. The optimum pH values were found to be 7.0 and 8 for free and immobilized lipases, respectively. Immobilized lipase was found to retain significant activity even after the seventh use. In the final section of the study, optically pure compounds were obtained by carrying out the enantioselective hydrolysis studies of racemic esters by using immobilized lipase. Enantiomeric excesses of the products in the enantioselective hydrolysis of racemic ibuprofen and naproxen methyl ester and racemic butyl mandelate were determined to be 94.93, 77.30 and 68.15, respectively.

Efficient continuous-flow aldehyde tag conversion using immobilized formylglycine generating enzyme

Immobilized formylglycine generating enzyme for efficient aldehyde tag conversion under continuous flow conditions.

Soluble enzyme cross-linking via multi-component reactions: a new generation of cross-linked enzymes

Production of CLEs using a multi-component reaction.

Magnetic nanoparticles as versatile carriers for enzymes immobilization: A review

Enzymes are highly efficient biocatalysts and widely employed in biotechnological sectors. However, lack of (re)-purification and efficient recovery of enzymes are among the most critical and challenging aspects, which render them enormously expensive for industrial exploitability. Aiming to tackle these challenges, magnetic nanoparticles (MNPs) have gained a special place as versatile carriers and supporting matrices for immobilization purposes, owing to the exceptional properties of MNPs, such as large surface area, large surface-to-volume ratio, and mobility and high mass transference. More importantly, they can also be easily separated and recovered by applying an external magnetic field. Apart from their biocompatible micro-environment, the utilization of such MNPs represents a noteworthy green chemistry approach, since it lengthens the biocatalyst lifetime through multiple recovery cycles. According to the literature evidence, various modification and/or functionalization approaches have been developed to produce MNPs for the effective immobilization of a broad variety of industrially important enzymes and biomolecules with improved characteristics. Enzymes immobilized on MNPs displayed a wide-working pH and temperature range, as well as, improved thermal and storage stabilities than that of their pristine counterparts. Co-immobilization of multi-enzymes could also be accomplished through nanoparticle-based approaches. This review presents an updated outlook on the development and characterization of MNPs, in particular, iron-based MNPs-derived nano-constructs as support materials for enzyme immobilization.

Immobilization of carbonic anhydrase on polyvinylidene fluoride membranes

In recent years, the application of carbonic anhydrase (CA) in CO₂ removal has attracted great interest. However, obtaining high enzyme recovery activity is difficult in existing immobilization techniques. In this work, water plasma-treated poly(vinylidene fluoride) (PVDF) membranes were modified via 3-aminopropyl triethoxy silane (KH550) or γ-(2, 3-epoxypropoxy) propyl trimethoxy silane (KH560), and then CA was attached. The immobilization process was optimized, and the catalytic properties of PVDF-attached CA were characterized. The maximum activity recovery of PVDF-KH550-CA was 60%, whereas that of PVDF-KH560-CA was 33%. The K_m values of PVDF-KH550-CA, PVDF-KH560-CA, and free enzyme were 9.97 ± 0.37, 12.5 ± 0.2, and 6.18 ± 0.23 mM, respectively, and their K_cat /K_m values were 206 ± 2, 117 ± 5, and 488 ± 4 M^-1 ·Sec^-1 . PVDF-attached CA shows excellent storage stability and reusability, and their half-life values were 82 and 78 days at 4 °C. At 25 °C, they were 50 and 37 days, respectively. PVDF-KH550-CA and PVDF-KH560-CA retained approximately 85% and 72% of the initial activity after undergoing 10 cycles. In the presence of them, the generation rates of CaCO₃ were 76% and 65% of the free CA system, which were 1.6 and 1.3 times that of the blank system, respectively. Its role in accelerating CO₂ sequestration holds great promise for its practical application.

Preparation of p-aminophenol modified superparamagnetic iron oxide nanoparticles for purification of α-amylase from the bovine milk

Currently, modified Fe₃O₄ magnetic nanoparticles frequently are used as nanocarriers for proteins and enzymes purification. In the present study, Fe₃O₄ magnetic nanoparticles were prepared, and their surfaces were modified with p-aminophenol affinity ligand immobilized by different linkers. The modified nanocarriers were used for the purification of α-amylase from the bovine milk (after precipitation the casein) by affinity purification. To evaluate the effectiveness of the p-aminophenol modified magnetic nanocarriers, the three different types of nanocarriers with different linkers having varying lengths were prepared. All nanocarriers were characterized and validated using FT-IR, SEM, EDX, VSM and XRD analysis methods According to our results, p-aminophenol ligand attached to the nanocarrier by long linkers better separates the α-amylase from the casein free skim milk with 49.66% recovery and 48.18-fold purification efficiency. The results of this study showed that our novel magnetic nanocarriers have the capacity to be used for fast, reproducible and cost-effective purification of α-amylase.

New Heterofunctional Supports Based on Glutaraldehyde-Activation: A Tool for Enzyme Immobilization at Neutral pH

Immobilization is an exciting alternative to improve the stability of enzymatic processes. However, part of the applied covalent strategies for immobilization uses specific conditions, generally alkaline pH, where some enzymes are not stable. Here, a new generation of heterofunctional supports with application at neutral pH conditions was proposed. New supports were developed with different bifunctional groups (i.e., hydrophobic or carboxylic/metal) capable of adsorbing biocatalysts at different regions (hydrophobic or histidine richest place), together with a glutaraldehyde group that promotes an irreversible immobilization at neutral conditions. To verify these supports, a multi-protein model system (E. coli extract) and four enzymes (Candidarugosa lipase, metagenomic lipase, β-galactosidase and β-glucosidase) were used. The immobilization mechanism was tested and indicated that moderate ionic strength should be applied to avoid possible unspecific adsorption. The use of different supports allowed the immobilization of most of the proteins contained in a crude protein extract. In addition, different supports yielded catalysts of the tested enzymes with different catalytic properties. At neutral pH, the new supports were able to adsorb and covalently immobilize the four enzymes tested with different recovered activity values. Notably, the use of these supports proved to be an efficient alternative tool for enzyme immobilization at neutral pH.

Magnetic separation: its application in mining, waste purification, medicine, biochemistry and chemistry

The use of strong magnetic field gradients and high magnetic fields generated by permanent magnets or superconducting coils has found applications in many fields such as mining, solid state chemistry, biochemistry and medical research.