Immobilization of catalase onto Eupergit C and its characterization

Catalytic Properties and Immobilization Studies of Catalase fromMalva sylvestrisL

Catalase was partially purified fromMalva sylvestrisL. and immobilized onto chitosan. Then, its catalytic properties were investigated. (NH4)2SO4precipitation and dialysis were performed in the extracted enzyme. Further purification was performed with sephadex G-200 column. Kinetic studies of the purified enzyme activity were measured and characterized. The inhibitory effects of KCN, NaN3, CuSO4, and EDTA onM. sylvestrisL. catalase activity were observed except NaCl. Furthermore,M. sylvestrisL. catalase was immobilized covalently with glutaraldehyde onto chitosan particles. The pH and temperature optima as well as the changes in the kinetics (Km, Vmax) of the immobilized and freeM. sylvestrisL. catalase were determined. The Km value for immobilized catalase (23.4 mM) was higher than that of free enzyme (17.6 mM). Optimum temperature was observed higher than that of the free enzyme. The optimum pH was the same for both free and immobilized catalases (pH 7.50). Immobilized catalase showed higher storage and thermal stabilities than free catalases. Free catalase lost all its activity within 60 days whereas immobilized catalase lost 45% of its activity during the same incubation period at 4°C. The remaining immobilized catalase activity was about 70% after 8 cycles of batch operations.

A rapid technique for assessing assimilable organic carbon of UV/H2O2-treated water

A rapid technique was adopted and customized to assess the assimilable organic carbon (AOC) content of water for UV/H2O2 treatment applications. Indigenous consortium was used as inoculum and cells grown were counted using flow cytometry. Residual H2O2 after UV/H2O2 treatment was found to inhibit microorganisms' regrowth, leading to incorrect AOC measurement. Therefore, Catalase immobilized on a polymeric support was used to eliminate the residual H2O2 prior to the AOC bioassay without affecting the water quality and the AOC. The choice of microbial consortium was found to influence the result of the AOC bioassay, suggesting that indigenous inoculum should be used for each individual sample set. Three days of incubation at 30°C were enough for the microorganisms to reach their stationary phase. Addition of minerals was found to be necessary, affecting the outcome of the AOC test. The method presented in this article will be valuable for monitoring AOC levels at different stages of water treatment train, especially when UV/H2O2 is used as one of treatment steps.

Impact of UV/H₂O₂ advanced oxidation treatment on molecular weight distribution of NOM and biostability of water

The presence of natural organic matter (NOM) poses several challenges to the commercial practice of UV/H(2)O(2) process for micropollutant removal. During the commercial application of UV/H(2)O(2) advanced oxidation treatment, NOM is broken down into smaller species potentially affecting biostability by increasing Assimilable Organic Carbon (AOC) and Biodegradable Organic Carbon (BDOC) of water. This work investigated the potential impact of UV/H(2)O(2) treatment on the molecular weight distribution of NOM and biostability of different water sources. A recently developed flow cytometric method for enumeration of bacteria was utilized to assess biological stability of the treated water at various stages through measurement of AOC. BDOC was also assessed for comparison and to better study the biostability of water. Both AOC and BDOC increased by about 3-4 times over the course of treatment, indicating the reduction of biological stability. Initial TOC and the source of NOM were found to be influencing the biostability profile of the treated water. Using high performance size exclusion chromatography, a wide range of organic molecule weights were found responsible for AOC increase; however, low molecular weight organics seemed to contribute more. Positive and meaningful correlations were observed between BDOC and AOC of different waters that underwent different treatments.

Metal-organic coordination-enabled layer-by-layer self-assembly to prepare hybrid microcapsules for efficient enzyme immobilization

A novel layer-by-layer self-assembly approach enabled by metal-organic coordination was developed to prepare polymer-inorganic hybrid microcapsules. Alginate was first activated via N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) coupling chemistry, and subsequently reacted with dopamine. Afterward, the dopamine modified alginate (Alg-DA) and titanium(IV) bis(ammonium lactato) dihydroxide (Ti(IV)) were alternatively deposited onto CaCO3 templates. The coordination reaction between the catechol groups of Alg-DA and the Ti(IV) allowed the alternative assembly to form a series of multilayers. After removing the templates, the alginate-titanium hybrid microcapsules were obtained. The high mechanical stability of hybrid microcapsules was demonstrated by osmotic pressure experiment. Furthermore, the hybrid microcapsules displayed superior thermal stability due to Ti(IV) coordination. Catalase (CAT) was used as model enzyme, either encapsulated inside or covalently attached on the surface of the resultant microcapsules. No CAT leakage from the microcapsules was detected after incubation for 48 h. The encapsulated CAT, with a loading capacity of 450-500 mg g(-1) microcapsules, exhibited desirable long-term storage stability, whereas the covalently attached CAT, with a loading capacity of 100-150 mg g(-1) microcapsules, showed desirable operational stability.

Continuous steroid biotransformations in microchannel reactors

The use of microchannel reactor based technologies within the scope of bioprocesses as process intensification and production platforms is gaining momentum. Such trend can be ascribed a particular set of characteristics of microchannel reactors, namely the enhanced mass and heat transfer, combined with easier handling and smaller volumes required, as compared to traditional reactors. In the present work, a continuous production process of 4-cholesten-3-one by the enzymatic oxidation of cholesterol without the formation of any by-product was assessed. The production was carried out within Y-shaped microchannel reactors in an aqueous-organic two-phase system. Substrate was delivered from the organic phase to aqueous phase containing cholesterol oxidase and the product formed partitions back to the organic phase. The aqueous phase was then forced through a plug-flow reactor, containing immobilized catalase. This step aimed at the reduction of hydrogen peroxide formed as a by-product during cholesterol oxidation, to avoid cholesterol oxidase deactivation due to said by-product. This setup was compared with traditional reactors and modes of operation. The results showed that microchannel reactor geometry outperformed traditional stirred tank and plug-flow reactors reaching similar conversion yields at reduced residence time. Coupling the plug-flow reactor containing catalase enabled aqueous phase reuse with maintenance of 30% catalytic activity of cholesterol oxidase while eliminating hydrogen peroxide. A final production of 36 m of cholestenone was reached after 300 hours of operation.

Enzyme-nanoporous gold biocomposite: excellent biocatalyst with improved biocatalytic performance and stability

BACKGROUND

Applications involving biomolecules, such as enzymes, antibodies, and other proteins as well as whole cells, are often hampered by their unstable nature at extremely high temperature and in organic solvents.

METHODOLOGY/PRINCIPAL FINDINGS

We constructed enzyme-NPG biocomposites by assembling various enzymes onto the surface of nanoporous gold (NPG), which showed much enhanced biocatalytic performance and stability. Various enzymes with different molecular sizes were successfully tethered onto NPG, and the loadings were 3.6, 3.1 and 0.8 mg g(-1) for lipase, catalase and horseradish peroxidase, respectively. The enzyme-NPG biocomposites exhibited remarkable catalytic activities which were fully comparable to those of free enzymes. They also presented enhanced stability, with 74, 78 and 53% of enzymatic activity retained after 20 successive batch reactions. Moreover, these novel biocomposites possessed significantly enhanced reaction durability under various thermal and in organic solvent systems. In a sample transesterification reaction, a high conversion rate was readily achieved by using the lipase-NPG biocomposite.

CONCLUSION/SIGNIFICANCE

These nano-biocomposite materials hold great potential in applications such as biosensing, molecular electronics, catalysis, and controlled delivery.

Immobilization of catalase via adsorption on poly(styrene-d-glycidylmethacrylate) grafted and tetraethyldiethylenetriamine ligand attached microbeads

Fibrous poly(styrene-d-glycidylmethacrylate) (P(S-GMA)) brushes were grafted on poly(styrene-divinylbenzene) (P(S-DVB)) beads using surface initiated-atom transfer radical polymerization (SI-ATRP). Tetraethyldiethylenetriamine (TEDETA) ligand was incorporated on P(GMA) block. The multi-modal ligand attached beads were used for reversible immobilization of catalase. The influences of pH, ionic strength and initial catalase concentration on the immobilization capacities of the P(S-DVB)-g-P(S-GMA)-TEDETA beads have been investigated. Catalase adsorption capacity of P(S-DVB-g-P(S-GMA)-TEDETA beads was found to be 40.8 ± 1.7 mg/g beads at pH 6.5 (with an initial catalase concentration 1.0mg/mL). The K(m) value for immobilized catalase on the P(S-DVB-g-P(S-GMA)-TEDETA beads (0.43 ± 0.02 mM) was found about 1.7-fold higher than that of free enzyme (0.25 ± 0.03 mM). Optimum operational temperature and pH was increased upon immobilization. The same support was repeatedly used five times for immobilization of catalase after regeneration without significant loss in adsorption capacity or enzyme activity.