Enzymatic hydrolysis of organophosphate insecticides, a possible pesticide disposal method.

A crude cell extract from a mixed bacterial culture growing on parathion, an organophosphate insecticide, hydrolyzed parathion (21 C) at a rate of 416 nmol/min per mg of protein. This rate of enzymatic hydrolysis, when compared with chemical hydrolysis by 0.1 N sodium hydroxide at 40 C, was 2, 450 times faster. Eight of 12 commonly used organophosphate insecticides were enzymatically hydrolyzed with this enzyme preparation at rates ranging from 12 to 1,360 nmol/min per mg of protein. Seven pesticides were hydrolyzed at rates significantly higher (40 to 1,005 times faster) than chemical hydrolysis. The pH optimum for enzymatic hydrolysis of the eight pesticides ranged from 8.5 to 9.5, with less than 50% of maximal activity expressed at pH 7.0. Maximal enzyme activity occurred at 35 C. The crude extract lost its activity at the rate of only 0.75%/day when stored at 6 C. Eight organic solvents, ranging from methanol to hexane, at low concentrations stimulated enzymatic hydrolysis by 3 to 20%, whereas at higher concentrations (1,000 mg/liter) they inhibited the reaction (9 to 50%). Parathion metabolites p-nitrophenol, hydroquinone, and diethylthiophosphoric acid, at up to 100-mg/liter concentrations, did not significantly influence enzyme activity.     

Detoxification of organophosphate pesticides using an immobilized phosphotriesterase from Pseudomonas diminuta

A purified phosphotriesterase was successfully immobilized onto trityl agarose in a fixed bed reactor. A total of up to 9200 units of enzyme activity was immobilized onto 2.0 mL of trityl agarose (65 mumol trityl groups/mL agarose), where one unit is the amount of enzyme required to catalyze the hydrolysis of one micromole of paraoxon in one min. The immobilized enzyme was shown to behave chemically and kinetically similar to the free enzyme when paraoxon was utilized as a substrate. Several organophosphate pesticides, methyl parathion, ethyl parathion, diazinon, and coumaphos were also hydrolyzed by the immobilized phosphotriesterase. However, all substrates exhibited an affinity for the trityl agarose matrix. For increased solubility and reduction in the affinity of these pesticides for the trityl agarose matrix, methanol/water mixtures were utilized. The effect of methanol was not deleterious when concentrations of less than 20% were present. However, higher concentrations resulted in elution of enzyme from the reactor. With a 10-unit reactor, a 1.0 mM paraoxon solution was hydrolyzed completely at a flow rate of 45 mL/h. Kinetic parameters were measured with a 0.1-unit reactor with paraoxon as a substrate at a flow rate of 22 mL/h. The apparent K(m) for the immobilized enzyme was 3-4 times greater than the K(m) (0.1 mM) for the soluble enzyme. Immobilization limited the maximum rate of substrate hydrolysis to 40% of the value observed for the soluble enzyme. The pH-rate profiles of the soluble and immobilized enzymes were very similar. The immobilization of phosphotriesterase onto trityl agarose provides an effective method esterase onto trityl agarose provides an effective method for hydrolyzing and thus detoxifyuing organophosphate pesticides and mammalian acetylcholinesterase inhinbitors.     

Production of parathion hydrolase activity

Summary A mixed bacterial culture which was obtained in a previous enrichment grew on parathion, an organophosphate insecticide, as a sole carbon and energy source. A cell-free enzyme preparation from this culture detoxified by hydrolysis eight commercially used organophosphate insecticides.Fermentation procedures for the production of this parathion hydrolase activity were examined to determine if this enzyme activity could be produced economically. The mixed culture was grown using sterile or non-sterile procedures in 4 or 11 continuous and batch culture fermentations. A pure Pseudomonas sp isolated from the mixed culture expressed parathion hydrolase activity when grown under axenic fermentation conditions on industrially used media such as meat extract, soya bean meal, and corn extract. The optimal conditions for production of parathion hydrolase activity were determined for both pure and mixed cultures. The yield of parathion hydrolase activity/ of fermentation broth per hour was improved 22 fold by growing the pure culture on an industrial meat extract medium instead of the mixed culture on parathion.     

Effects of external diffusion and design geometry on the performance of immobilized glucose isomerase reactor system

Using immobilized glucose isomerase, the effects of superficial velocity of the reaction solution flowing through a packed-bed reactor on the apparent kinetic constants of reversible reaction system were studied. The results showed that the apparent kinetic constants, both V_m″ and K_m″, of the forward reaction varied significantly as the superficial velocity is changed, whereas those of the reverse reaction varied only slightly. Using the kinetic data determined experimentally, computer simulation of the enzyme reactor performance was carried out, and the importance of the external mass transfer in the proximity of immobilized-enzyme particles was recognized. The reactor performance, expressed in terms of productivity, was examined as a function of the reactor height-to-diameter ratio, H/D. The productivity of the reactor system goes through a maximum value at a H/D ratio of about 1.6. and decreases as the H/D ratio increases. Theoretical analysis of the reaction kinetics of immobilized-enzyme system that has reversible reaction kinetics is also presented. The experimental results showed good agreement with the results found from the theoretical analysis and the computer simulation studies. Based on the principles of the methods and the results presented in this paper, it is anticipated that one can predict the optimal design and operating conditions for the glucose isomerase reactor system and that application of the results could be extended to other enzyme systems with reversible reaction kinetics.     

Kinetics of enzymatic degradation of cyanide

CYANIDASE(@) is a new enzyme preparation capable of degrading cyanide in industrial wastewaters to ammonia and formate in an apparently one-step reaction, down to very low concentrations. This enzyme has both a high selectivity and affinity toward cyanide. A granular form of the biocatalyst was used in a recirculation fixed bed reactor in order to characterize the new biocatalyst with respect to pH, ionic strength, common ions normally present in wastewaters, mass transfer effects, and temperature. Long term stability was investigated. The kinetics of the enzymatic degradation of cyanide were studied in a batch reactor using the powdered immobilized enzyme preparation and modeled using a simple Michaelis-Menten equation.     

The application of constant recycle solids concentration in activated sludge process.

The applicability of the model derived by Ramanathan and Gaudy (Biotechnol. Bioeng., 11, 207, (1969)) for completely mixed activated sludge treatment holding the recycle solids concentration as a system constant was investigated using an actual industrial organic wastewater. Short-term experiments were conducted at various dilution rates (1/8, 1/6, 1/4, 1/2, 1/1.5 hr-1) for two recycle solids concentration values (5000 and 7000 mg/liter). The influent substrate concentration was maintained at 1000 mg/liter COD and the hydraulic recycle ratio- alpha, was kept at 0.3. It was found that for bottling plant (Pepsi Cola) wastewaters, a steady state with respect to reactor biological solids and effluent COD, at different dilution rates, could be attained, lending experimental evidence to the assumption that a steady state could be reached in developing the model and also affecting the applicability of the model in industrial organic wastewater. The reactor biological solids and effluent COD calculated from the model closely agreed with the observed values at dilution rates lower than 0.5 hr-1. Operation at dilution rates higher than 0.5 hr-1 will washout the biological solids from the reactor and the recycle substrate concentration will be apparent if the concentration of XR were not increased.     

An immobilized hydrogenase from Alcaligenes eutrophus H-16

Alcaligenes Eutrophus H-16 was grown in continuous culture under conditions which induced hydrogenase production. The hydrogenase enzyme was extracted, partially purified and immobilized on porous glass. This enzyme was then studied both in solution and in immobilized form as a possible candidate for a number of industrial applications. It proved to have a stability (storage and operational) which was highly temperature dependent. Temperatures near freezing caused the enzyme to retain its activity for long periods of time. Although its kinetics were more favorable at elevated temperatures of up to 40 degrees C, the loss of stability outweighed this gain substantially. The effects of buffer type and pH on enzyme activity were also studied. This enzyme has only a modest sensitivity to destruction by oxygen during storage, in contrast to hydrogenases produced by several other microorganisms.     

The effect of lead on the calcium-handling capacity of rat heart mitochondria.

1. Glucose 6-phosphate dehydrogenase (D-glucose 6-phosphate-NADP+ oxidoreductase, EC 1.1.1.49) from baker's yeast (Saccharomyces cerevisiae) was immobilized on CNBr-activated Sepharose 4B with retention of about 3% of enzyme activity. This uncharged preparation was stable for up to 4 months when stored in borate buffer, pH7.6, at 4 degrees C. 2. Stable enzyme preparations with negative or positive overall charge were made by adding valine or ethylenediamine to the CNBr-activated Sepharose 4B 30min after addition of the enzyme. 3. These three immobilized enzyme preparations retained 40-60% of their activity after 15 min at 50 degrees C. The soluble enzyme is inactivated by these conditions. 4. The soluble enzyme lost 45 and 100% of its activity on incubation for 3h at pH6 and 10 respectively. The three immobilized-enzyme preparations were completely stable over this entire pH range. 5. The pH optimum of the positively and negatively charged immobilized-enzyme preparations were about 8 and 9 respectively. The soluble enzyme and the uncharged immobilized enzyme had an optimum pH at about 8.5 6. Glucose 6-phosphate dehydrogenase immobilized on CNBr-activated Sephadex G-25 was unstable, as was enzyme attached to CNBr-activated Sepharose 4B to which glycine, asparitic acid, valine or ethylenediamine was added at the same time as the enzyme.     

Comparative anaerobic treatment of wastewater from pharmaceutical, brewery, paper and amino acid producing industries

This study concerned the anaerobic treatment of five different industrial wastewaters with a diverse and complex chemical composition. The kinetics of biotransformation of this wastewater at different chemical oxygen demand (COD) were studied in a batch reactor. Wastewater from an amino acid producing industry (Fermex) and from a tank that received several types of wastewaters (collector) contained 0.83 g l(-1) and 0.085 g l(-1) sulfate, respectively. During the study period of 20 days, methane formation was observed in all types of wastewaters. Studies on COD biodegradation showed the reaction velocity was higher for Fermex wastewater and lower for collector wastewater, with values of 0.0022 h(-1) and 0.0011 h(-1), respectively. A lower methanogenic activity of 0.163 g CH4 day(-1) g(-1) volatile suspended solids (VSS) and 0.20 g CH4 day(-1) g(-1) VSS, respectively, was observed for paper producing and brewery wastewater. Adapted granular sludge showed the best biodegradation of COD during the 20-day period. The sulfate-reducing activity in pharmaceutical and collector wastewater was studied. A positive effect of sulfate-reducing activity on methanogenic activity was noted for both types of wastewaters, both of which contained sulfate ions. All reactions of methane generation for the tested industrial wastewaters were first-order. The results of this study suggest that the tested wastewaters are amenable to anaerobic treatment.     

Biotechnological process for production of beta-dipeptides from cyanophycin on a technical scale and its optimization

A triphasic process was developed for the production of beta dipeptides from cyanophycin (CGP) on a large scale. Phase I comprises an optimized acid extraction method for technical isolation of CGP from biomass. It yielded highly purified CGP consisting of aspartate, arginine, and a little lysine. Phase II comprises the fermentative production of an extracellular CGPase (CphE(al)) from Pseudomonas alcaligenes strain DIP1 on a 500-liter scale in mineral salts medium, with citrate as the sole carbon source and CGP as an inductor. During optimization, it was shown that 2 g liter(-1) citrate, pH 6.5, and 37 degrees C are ideal parameters for CphE(al) production. Maximum enzyme yields were obtained after induction in the presence of 50 mg liter(-1) CGP or CGP dipeptides for 5 or 3 h, respectively. Aspartate at a concentration of 4 g liter(-1) induced CphE(al) production with only about 30% efficiency in comparison to that with CGP. CphE(al) was purified utilizing its affinity for the substrate and its specific binding to CGP. CphE(al) turned out to be a serine protease with maximum activity at 50 degrees C and at pH 7 to 8.5. Phase III comprises degradation of CGP to beta-aspartate-arginine and beta-aspartate-lysine dipeptides with a purity of over 99% (by thin-layer chromatography and high-performance liquid chromatography), employing a crude CphE(al) preparation. Optimum degradation parameters were 100 g liter(-1) CGP, 10 g liter(-1) crude CphE(al) powder, and 4 h of incubation at 50 degrees C. The overall efficiency of phase III was 91%, while 78% (wt/wt) of the used CphE(al) powder with sustained activity toward CGP was recovered. The optimized process was performed with industrial materials and equipment and is applicable to any desired scale.     

Comparative anaerobic treatment of wastewater from pharmaceutical,brewery, paper and amino acid producing industries

This study concerned the anaerobic treatment of five different industrial wastewaters with a diverse and complex chemical composition. The kinetics of biotransformation of this wastewater at different chemical oxygen demand (COD) were studied in a batch reactor. Wastewater from an amino acid producing industry (Fermex) and from a tank that received several types of wastewaters (collector) contained 0.83 g l⁻¹ and 0.085 g l⁻¹ sulfate, respectively. During the study period of 20 days, methane formation was observed in all types of wastewaters. Studies on COD biodegradation showed the reaction velocity was higher for Fermex wastewater and lower for collector wastewater, with values of 0.0022 h⁻¹ and 0.0011 h⁻¹, respectively. A lower methanogenic activity of 0.163 g CH₄ day⁻¹ g⁻¹ volatile suspended solids (VSS) and 0.20 g CH₄ day⁻¹ g⁻¹ VSS, respectively, was observed for paper producing and brewery wastewater. Adapted granular sludge showed the best biodegradation of COD during the 20-day period. The sulfate-reducing activity in pharmaceutical and collector wastewater was studied. A positive effect of sulfate-reducing activity on methanogenic activity was noted for both types of wastewaters, both of which contained sulfate ions. All reactions of methane generation for the tested industrial wastewaters were first-order. The results of this study suggest that the tested wastewaters are amenable to anaerobic treatment.

     

Characterization of a novel organophosphorus hydrolase from Nocardiodes simplex NRRL B-24074

We characterized a novel organophosphorus hydrolase (OPH) activity expressed by Nocardiodes simplex NRRL B-24074, a member of a coumaphos-degrading microbial consortium from cattle dip waste. Like the previously characterized OPH from Nocardia sp. strain B- (NRRL B- 16944), OPH activity in N. simplex is located in the cytoplasm and is expressed constitutively. The purified enzyme is monomeric, has a native molecular size of 45,000 Da and has a specific activity toward ethyl parathion of 33 micromole/min x mg protein. Km constants for the enzyme with the structurally related organophosphate pesticides ethyl parathion and EPN were 100 microM and 345 microM, respectively. Although OPH activity in extracts did not require the addition of divalent cations, the purified enzyme lost activity during dialysis against phosphate buffer and this activity could be restored after incubation in buffer containing either CoSO4 or CuSO4. Our results suggest that OPH activity in N. simplex is distinct from other known OPHs and that the responsible gene is unrelated to known genes.     

Esterases in marine dinoflagellates and resistance to the organophosphate insecticide parathion.

Esterases are involved in the susceptibility or resistance of organisms to organophosphate pesticides. We have examined the action of parathion on the marine dinoflagellates Crypthecodinium cohnii and Prorocentrum micans by looking at their esterases. One-dimensional gel electrophoresis, immunoblotting and cytochemistry plus image analysis were used to characterize the nature and distribution of the enzymes. Esterases were found in both species, but there appeared to be no particular intracellular localization. The esterase activity of the heterotrophic species Crypthecodinium cohnii was 30-fold greater than that of the autotrophic Prorocentrum micans and had an antigenic site in common with mosquito esterase. The resistance of Crypthecodinium cohnii to parathion was specific and reversible. Less parathion entered the parathion-resistant Crypthecodinium cohnii cells than the untreated control cells. Parathion-resistant cell extracts of Crypthecodinium cohnii analyzed after immunoblotting also contained an additional band of esterase activity. These results confirm the importance of esterases in toxicological studies of organophosphate insecticides, especially those of marine dinoflagellates.     

Continuous regeneration of ATP in enzyme membrane reactor for enzymatic syntheses

This work shows that the enzyme membrane reactor offers the opportunity to carry out the enzymatic regeneration of ATP providing continuous operation with high performance. In this system, the coenzyme is immobilized on a water-soluble polymer. These high-molecular weight derivates are entrapped within an ultrafiltration membrane together with the enzymes for production of regeneration. Several polymer derivatives of ATP have been prepared for this immobilization technique. Coenzymatic activity of these derivatives was studied with several enzymes for both ATP-requiring and ATP-regenerating reactions. PEG-N6-aminohexyl-ATP was selected as the appropriate coenzyme for operating the enzyme membrane reactor. Acetate kinase was the only enzyme providing enough activity for regeneration. Production of glucose-6-phosphate is cited as the first example. The kinetics of acetate kinase and hexokinase were examined and used to choose the operating conditions of the process. The process operated continuously for more than 1 month. With a mean conversion of 80%, the space-time yield amounted to 348 g glucose-6-phosphate/L d. The cycle number of ATP was estimated as 20, 000 mol/mol. With the continuous production of gamma-glutamylcysteine and NADP, the feasibility of the system was proven.     

Lipase kinetics: hydrolysis of triacetin by lipase from Candida cylindracea in a hollow-fiber membrane reactor

The aptitude of a hollow-fiber membrane reactor to determine lipase kinetics was investigated using the hydrolysis of triacetin catalyzed by lipase from Canadida cylindracea as a model system. The binding of the lipase to the membrane appears not to be very specific (surface adsorption), and probably its conformation is hardly altered by immobilization, resulting in an activity comparable to that of the enzyme in its native form. The reaction kinetics defined on the membrane surface area were found to obey Michaelis-Menten kinetics. The specific activity of the lipase in the membrane reactor was found to be significantly higher than in an emulsion reactor. The activity and stability of the enzyme immobilized on a hydrophilic membrane surface seem not to be influenced significantly by the choice of the membrane material. The hollow-fiber membrane reactor is a suitable tool to assess lipase kinetics in a fast and convenient way.     

Characterization and inhibition studies of an α-carbonic anhydrase from the endangered sturgeon species Acipenser gueldenstaedti

An α-carbonic anhydrase (CA, EC 4.2.1.1) was purified and characterized kinetically from erythrocytes of the sturgeon Acipenser gueldenstaedti, an endangered species. The sturgeon enzyme (AgCA) showed kinetic parameters for the CO(2) hydration reaction comparable with those of the human erythrocytes enzyme hCA II, being a highly active enzyme, whereas its esterase activity with 4-nitrophenyl acetate as substrate was lower. Sulphonamide inhibitors (acetazolamide, sulphanilamide) strongly inhibited AgCA, whereas metal ions (Ag(+), Zn(2+), Cu(2+) and Co(2+)) were weak, millimolar inhibitors. Several widely used pesticides (2,4-dichlorophenol, dithiocarbamates, parathion and carbaryl) were also assayed as inhibitors of this enzyme. The dithiocarbamates were low micromolar AgCA inhibitors (IC(50) of 16-18 μM), whereas the other pesticides inhibited the enzyme with IC(50)s in the range of 102-398 μM. The wide use of dithiocarbamate pesticides may be one of the factors enhancing the vulnerability of this sturgeon species to pollutants.     

甲基对硫磷降解菌假单胞菌WBC-3的筛选及其降解性能的研究

从农药污染土样中分离出的一株细菌具有彻底降解甲基对硫磷的能力。该菌经生理生化特性分析和16S rDNA序列同源性分析,鉴定为假单胞菌属,命名为Pseudomonas sp.WBC\|3。该菌在pH7～8、温度23℃～30℃范围内均生长良好,对甲基对硫磷的耐受浓度在单纯无机盐培养基中可达到800mg/L,在含有01%葡萄糖的培养基中可达到2000mg/L。该菌能够以甲基对硫磷作为唯一碳源、氮源,将其彻底降解作为生长基质,对于300mg/L甲基对硫磷的降解速度达15mg/L\5h,于22h后达到其稳定生长期。该菌对于多种有机磷农药及部分芳烃类化合物具有生化代谢能力。从该菌的细胞周质组分中纯化出的有机磷水解酶在SDSPAGE胶上显示为分子量约为33.5×103的条带。     

Microbial Metabolism of a Parathion-Xylene Pesticide Formulation

A mixed bacterial culture was adapted to growth on a mixed carbon substrate consisting of the pesticide parathion and its xylene-based formulation. The environmental growth parameters of temperature, pH, and dissolved oxygen concentration were optimized to obtain complete metabolism of parathion from this mixed carbon substrate. This adapted culture grew rapidly (mu = 0.7 per h) on the pesticide formulation at high parathion suspensions (3,000 mg/liter). Carbon utilization from this mixed substrate was strongly dependent on pH. At slightly acidic pH, xylene was preferentially metabolized, whereas at slightly alkaline pH, parathion was preferentially metabolized. Diethylthiophosphoric acid, a metabolite from parathion, and toluic acid, a metabolite from xylene, also influenced the selection of the primary carbon source.     

Glucose determination using immobilized polyphosphate glucokinase.

Polyphosphate glucokinase (EC 2.7.1.63, polyphosphate:glucose phosphotransferase) was covalently coupled to collagen-coated silica gel beads. The immobilized enzyme, as a packed-bed reactor, was used to determine glucose in serum and other samples. The method was based on a spectrophotometric measurement of NADPH produced by two consecutive reactions, similar to the hexokinase method. The described approach takes advantage of the greater stability of polyphosphate compared to that of ATP, the greater specificity of polyphosphate glucokinase versus that of hexokinase, and the reusability of the immobilized enzyme. Linearity, precision, and accuracy of the method were tested and found to be very good. The results were linear between 10 and 50 nmol of glucose in a 50-microliter sample and the coefficient of variation was less than 4% in five successive determinations. The recovery of glucose was about 100% after calibration of the method. The results of the measurements correlated well with those obtained with soluble polyphosphate glucokinase (r = 0.997, y = 1.036x - 0.016). The immobilized-enzyme reactor showed good operational stability during a month of use, losing about 12% of its initial activity.     

Sulphydryl oxidase: Properties and applications

Sulphydryl oxidase has been isolated and purified from bovine milk and partially characterized. The enzyme is obtained from the whey fraction produced by chymosin (rennin) treatment of skim milk. Several procedures have been developed for its isolation, all of which use to advantage its concentration-dependent aggregate size. This enzyme exhibits a much broader substrate specificity than that shown by other ‘aerobic oxidases’ presently characterized which catalyse the formation of disulphides from thiols. Using molecular oxygen as an electron acceptor in a twoelectron reduction to hydrogen peroxide, the enzyme catalyses oxidation of cysteine and its analogues, some volatile thiols, peptides, and also thiols in proteins.Vis-a-vis protein-disulphide oxidoreductase and protein-disulphide isomerase, this enzyme does not catalyse thiol-disulphide interchange and thus functions only in de novo formation of disulphides. Enzyme-bound iron and most likely a free sulphydryl group are essential for catalytic activity; however, the carbohydrate moiety of this glycoprotein is probably not required. The broad substrate specificity suggests several potential industrial uses for the enzyme, including flavour modification in the food industry or synthesis of disulphides in pharmaceuticals. Consequently, immobilized forms were developed and characterized. Reactors containing sulphydryl oxidase covalently immobilized on porous glass and silica have been examined for their efficacy in eliminating the cooked flavour in ultra-high temperature sterilized milk. Both the degree of oxidation and cooked flavour were correlated with a normalized residence time in the reactor.