生物膜法处理潮汐河道无序排放污水的研究

采用生物膜法处理潮汐河道无序排放的污水,考察不同水力停留时间和温度下,潮汐作用对反应池内生物膜生长情况影响和COD、NH3-N、TP的沿程分布规律,以及复合酶生物促进剂对反应系统处理效果的促进作用。结果显示在潮汐作用下,HRT=8 h,温度20℃和投加复合酶生物促进剂情况下,COD、NH3-N和TP的去除率分别为53.9%、46.7%和49.4%,分别比对照池高7.1%、13.2%和10.5%,表明生物膜法处理无序排放污水有较强的适应能力,复合酶生物促进剂能提升反应系统的处理效果。在相同温度下,水力停留时间越长,处理效果越好。     

The kinetics of enzyme catalyzed synthesis of sterol ester

The production of sterol ester by transesterification of β‐sitosterol with fish oil (TAG) catalyzed by Thermomyces lanuginosus immobilized lipase enzyme with varied reaction parameters such as temperature, substrate molar ratio, concentration of enzyme to deduce the enzyme kinetics for the reaction was investigated. For this transesterification reaction, the kinetic model was derived by using Ping Pong Bi Bi Mechanism. The K_m value from the first plot containing fish oil as substrate was 1.31 ± 0.05, while K_m from the second plot containing β‐sitosterol as substrate was 1.01 ± 0.04; identical V_max (0.213 ± 0.06) values were obtained by keeping one of the substrate concentration constant and varying the other. Practical applications : Deduction of reaction kinetics is an important criterion to ascertain the viability of any chemical process. Enzymatic processes need special attention to set model reaction parameters which could help in optimization or design of the actual process. In the present study we have derived the enzyme kinetics for the production sterol ester, an important nutraceutical, and calculated its K_m and V_max values along with the Arhenius activation energy to establish the viability of the reaction.     

Enzymatic membrane reactors: the determining factors in two separate phase operations

A two separate phase‐enzymatic membrane reactor is an attractive process since it has a large interfacial area and exchange surfaces, simultaneous reaction and separation and other benefits. Many factors influence its successful operation, and these include characteristics of the enzyme, membrane, circulating fluids and reactor operations. Although the operating conditions are the main factor, other factors must be considered before, during or after its application. At the initial stage of reactor development, the solubility of substrates and products, type of operation, membrane material and size, enzyme preparation and loading procedure, and cleanliness of the recirculated fluids should be specified. The immobilization site, reactor arrangement, dissolved or no‐solvent operation, classic or emulsion operation and immobilized or suspended enzyme(s) are determined later. Some factors still need further studies. Utilization of the technology is described for use from multigram‐ to plant‐scale capacity to process racemic and achiral compounds. The racemates were resolved primarily by kinetic resolution, but dynamic kinetic resolution has been exploited. The technology focused on hydrolytic reactions, but esterification processes were also exploited. Copyright © 2011 Society of Chemical Industry     

Vinyl triazole carrying metal‐chelated beads for the reversible immobilization of glucoamylase

Poly(ethylene glycol dimethacrylate–1‐vinyl‐1,2,4‐triazole) [poly(EGDMA–VTAZ)] beads with an average diameter of 100–200 μm were obtained by the copolymerization of ethylene glycol dimethacrylate (EGDMA) with 1‐vinyl‐1,2,4‐triazole (VTAZ). The copolymer hydrogel bead composition was determined by elemental analysis and was found to contain 5 EGDMA monomer units for each VTAZ monomer unit. The poly(EGDMA–VTAZ) beads were characterized by swelling studies and scanning electron microscopy (SEM). The specific surface area of the poly(EGDMA–VTAZ) beads was found 65.8 m²/g. Cu²⁺ ions were chelated on the poly(EGDMA–VTAZ) beads. The Cu²⁺ loading was 82.6 μmol/g of support. Cu²⁺‐chelated poly(EGDMA–VTAZ) beads with a swelling ratio of 84% were used in the immobilization of Aspergillus niger glucoamylase in a batch system. The maximum glucoamylase adsorption capacity of the poly(EGDMA–VTAZ)–Cu²⁺ beads was 104 mg/g at pH 6.5. The adsorption isotherm of the poly(EGDMA–VTAZ)–Cu²⁺ beads fitted well with the Langmuir model. Adsorption kinetics data were tested with pseudo‐first‐ and second‐order models. The kinetic studies showed that the adsorption followed a pseudo‐second‐order reaction model. The Michaelis constant value for the immobilized glucoamylase (1.15 mg/mL) was higher than that for free glucoamylase (1.00 mg/mL). The maximum initial rate of the reaction values were 42.9 U/mg for the free enzyme and 33.3 U/mg for the immobilized enzyme. The optimum temperature for the immobilized preparation of poly(EGDMA–VTAZ)–Cu²⁺–glucoamylase was 65°C; this was 5°C higher than that of the free enzyme at 60°C. The glucoamylase adsorption capacity and adsorbed enzyme activity slightly decreased after 10 batch successive reactions; this demonstrated the usefulness of the enzyme‐loaded beads in biocatalytic applications. The storage stability was found to increase with immobilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of Cu(II)‐chelated poly(vinyl alcohol) nanofibrous membranes for catalase immobilization

Poly(vinyl alcohol) (PVA) nanofibers were formed by electrospinning. Metal chelated nanofibrous membranes were prepared by reaction between Cu(II) solution and nanofibers, and which were used as the matrix for catalases immobilization. The constants of Cu(II) adsorption and properties of immobilized catalases were studied in this work. The Cu(II) concentration was determined by atomic absorption spectrophotometer (AAS), the immobilized enzymes were confirmed by the Fourier transform infrared spectroscopy (FTIR), and the amounts of immobilized enzymes were determined by the method of Bradford on an ultraviolet spectrophotometer (UV). Adsorption of Cu(II) onto PVA nanofibers was studied by the Langmuir isothermal adsorption model. The maximum amount of coordinated Cu(II) (q_m) was 2.1 mmol g⁻¹ (dry fiber), and the binding constant (K_l) was 0.1166 L mmol⁻¹. The immobilized catalases showed better resistance to pH and temperature inactivation than that of free form, and the thermal and storage stabilities of immobilized catalases were higher than that of free catalases. Kinetic parameters were analyzed for both immobilized and free catalases. The value of V_max (8425.8 μmol mg⁻¹) for the immobilized catalases was smaller than that of the free catalases (10153.6 μmol mg⁻¹), while the K_m for the immobilized catalases were larger. It was also found that the immobilized catalases had a high affinity with substrate, which demonstrated that the potential of PVA‐Cu(II) chelated nanofibrous membranes applied to enzyme immobilization and biosensors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

NAD+‐Dependent Dehydrogenase PctP and Pyridoxal 5′‐Phosphate Dependent Aminotransferase PctC Catalyze the First Postglycosylation Modification of the Sugar Intermediate in Pactamycin Biosynthesis

The unique five‐membered aminocyclitol core of the antitumor antibiotic pactamycin originates from d ‐glucose, so unprecedented enzymatic modifications of the sugar intermediate are involved in the biosynthesis. However, the order of the modification reactions remains elusive. Herein, we examined the timing of introduction of an amino group into certain sugar‐derived intermediates by using recombinant enzymes that were encoded in the pactamycin biosynthesis gene cluster. We found that the NAD⁺‐dependent alcohol dehydrogenase PctP and pyridoxal 5′‐phosphate dependent aminotransferase PctC converted N‐acetyl‐d ‐glucosaminyl‐3‐aminoacetophonone into 3′‐amino‐3′‐deoxy‐N‐acetyl‐d ‐glucosaminyl‐3‐aminoacetophenone. Further, N‐acetyl‐d ‐glucosaminyl‐3‐aminophenyl‐β‐oxopropanoic acid ethyl ester was converted into the corresponding 3′‐amino derivative. However, PctP did not oxidize most of the tested d ‐glucose derivatives, including UDP‐GlcNAc. Thus, modification of the GlcNAc moiety in pactamycin biosynthesis appears to occur after the glycosylation of aniline derivatives.     

Peptide‐Based Fluorescent Probes for Deacetylase and Decrotonylase Activity: Toward a General Platform for Real‐Time Detection of Lysine Deacylation

Histone deacetylases regulate the acetylation levels of numerous proteins and play key roles in physiological processes and disease states. In addition to acetyl groups, deacetylases can remove other acyl modifications on lysines, the roles and regulation of which are far less understood. A peptide‐based fluorescent probe for single‐reagent, real‐time detection of deacetylase activity that can be readily adapted for probing broader lysine deacylation, including decrotonylation, is reported. Following cleavage of the lysine modification, the probe undergoes rapid intramolecular imine formation that results in marked optical changes, thus enabling convenient detection of deacylase activity with good statistical Z′ factors for both absorption and fluorescence modalities. The peptide‐based design offers broader isozyme scope than that of small‐molecule analogues, and is suitable for probing both metal‐ and nicotinamide adenine dinucleotide (NAD⁺)‐dependent deacetylases. With an effective sirtuin activity assay in hand, it is demonstrated that iron chelation by Sirtinol, a commonly employed sirtuin inhibitor, results in an enhancement in the inhibitory activity of the compound that may affect its performance in vivo.     

Effective Release of Intracellular Enzymes by Permeating the Cell Membrane with Hydrophobic Deep Eutectic Solvents

An efficient and green method is crucial for the recovery of intracellular biological products. The major drawbacks of the conventional cell disruption method are nonselectivity and enzyme denaturation. The permeability of hydrophobic deep eutectic solvents (DESs) to the cell membrane was studied, for the first time, and then hydrophobic DESs were innovatively applied to release intracellular enzymes from recombinant Escherichia coli. After optimization, a DES suspension of l -menthol/oleic acid (0.5 %, v/v) showed the highest release yield of intracellular enzyme. Compared with that released by sonication, a release yield of phospholipase D (PLD) of up to 114.58 % was achieved, and the specific activity was increased by 1.96 times. The microstructure of the cell membrane under different treatments was observed by using an electron microscope to understand the permeation of DESs to the cell membrane. The feasibility and applicability of the proposed release method in industrial applications were also demonstrated. The effective and green release method of intracellular enzymes developed herein has bright prospects for industrial application to replace traditional cell disruption methods. A preliminary study on the permeability of hydrophobic DESs to the cell membrane showed that there would be a potential application prospect of hydrophobic DESs not only in releasing intracellular contents, but also in seeking new green penetrating agents.     

Melatonin Application Modifies Antioxidant Defense and Induces Endoreplication in Maize Seeds Exposed to Chilling Stress

The aim of the study was to demonstrate the biostimulating effect of exogenous melatonin (MEL) applied to seeds via hydroconditioning. It was indicated that only well-chosen application technique and MEL dose guarantees success concerning seed germination and young seedlings growth under stress conditions. For maize seed, 50 μM of MEL appeared to be the optimal dose. It improved seed germination and embryonic axes growth especially during chilling stress (5 °C/14 days) and during regeneration after its subsided. Unfortunately, MEL overdosing lowered IAA level in dry seeds and could disrupt the ROS-dependent signal transduction pathways. Very effective antioxidant MEL action was confirmed by low level of protein oxidative damage and smaller quantity of lipid oxidation products in embryonic axes isolated from seeds pre-treated with MEL and then exposed to cold. The stimulatory effects of MEL on antioxidant enzymes: SOD, APX and GSH-PX and on GST-a detoxifying enzyme, was also demonstrated. It was indicated for the first time, that MEL induced defence strategies against stress at the cytological level, as appearing endoreplication in embryonic axes cells even in the seeds germinating under optimal conditions (preventive action), but very intensively in those germinating under chilling stress conditions (intervention action), and after stress removal, to improve regeneration.