Synergistic interaction between two bacterial isolates in the degradation of carbofuran

The dominant bacteriaPseudomonas sp. andArthrobacter sp. were isolated from the standing water of carbofuran-retreatedAzolla plot.Arthrobacter sp. hydrolysed carbofuran added to the mineral salts medium as a sole source of carbon and nitrogen while no degradation occurred withPseudomonas sp. Interestingly, when the medium containing carbofuran was inoculated with bothArthrobacter sp. andPseudomonas sp., a synergistic increase in its hydrolysis and subsequent release of CO₂ from the side chain was noticed. This synergistic interaction was better expressed at 25° C than at 35° C. Likewise, related carbamates, carbaryl, bendiocarb and carbosulfan were more rapidly degraded in the combined presence of both bacterial isolates.     

Stimulation of Methanogenesis by Aldicarb and Several Other N-Methyl Carbamate Pesticides

Aldicarb and several other N-methyl carbamate pesticides stimulated methane production in anaerobic salt marsh soils and organic-rich aquifer soils. Stimulation was biological and linearly related to the amount of carbamate added. Of the four carbamates studied, methomyl gave the greatest stimulation followed by carbaryl, aldicarb, and baygon. The percent conversions [(moles of CH₄ in excess of control/mole of carbamate added) × 100] for methomyl, carbaryl, aldicarb, and baygon were 88, 57, 40, and 11, respectively. Using aldicarb as a model carbamate, we found that monomethylamine (MA) accumulated in sediments as a result of aldicarb addition. MA arises from the N-methyl carbamoyl portion of the carbamates as a result of presumptive biological hydrolysis. MA levels decreased as CH₄ production was stimulated, and 2-bromoethane sulfonic acid (a specific inhibitor of mathanogenesis) partially inhibited the loss of MA. These findings suggest that N-methyl carbamates are readily hydrolyzed to MA in the presence of an active microbial population under anaerobic conditions and that methanogenesis is stimulated as a result of the consumption of MA by methanogenic bacteria.     

Bioaugmentation of carbofuran residues in soil using Burkholderia cepacia PCL3 adsorbed on agricultural residues

Burkholderia cepacia PCL3 (GenBank accession number of EF990634) is a carbofuran degrader isolated from phytoremediated rhizosphere soil in our laboratory. Free and the immobilized PCL3 on corncob and sugarcane bagasse were investigated for their abilities to degrade carbofuran in Basal Salt Medium (BSM) and soil microcosm. The reusability and survival of immobilized PCL3 in comparison to free cells were also examined. Short half-lives (t_1/2) of carbofuran of 3–4 d in BSM were obtained using the isolate PCL3 in both free and immobilized cell forms. Immobilized cells could survive (10⁶–10⁷ cfu ml^?1) through 30 d of incubation, while the number of free cells decreased continuously after 10 d. Immobilized B. cepacia PCL3 could be reused twice without loss in their abilities to degrade carbofuran in BSM, which suggested an advantage of using immobilized cell over free cell. Free and immobilized cells were augmented into soil and showed an effective capability to remediate carbofuran residues, both of which indicated by 5-folds decrease in carbofuran half-lives in augmented soil. Immobilization of PCL3 on corncob and sugarcane bagasse provided the possibilities of reusing the cells as well as improving the cell survival without decreasing carbofuran degradation activity.     

Biodegradation of Carbofuran phenol by free and immobilized cells of <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> ATCC13883T

The Klebsiella sp. strain ATCC13883T capable of degrading carbofuran phenol (2,3-dihydro-2,2-dimethylbenzofuran-7-ol) has been separated from the soil by enrichment culture technique and immobilized in various, namely polyurethane foam (PUF), polyacrylamide, alginate, agar and alginate-bentonite clay-powdered activated charcoal (PAC). The degradation rates of 20 and 30 mM carbofuran phenol by free and immobilized cells in batch and semi-continuous shaken cultures were compared. The PUF-immobilized cells achieved higher degradation rates in a shorter time than freely suspended cells and the cells immobilized in polyacrylamide, alginate and agar. The PUF- and alginate-bentonite clay-PAC-immobilized cells could be reused for more than 36 cycles, polyacrylamide-entrapped cells for 20 cycles and alginate-bentonite-PAC 28 cycles, without losing any degradation capacity and showed better tolerance to pH, temperature and concentration changes than free cells. These results showed that cells immobilized in modified alginate-bentonite-PAC immobilizers tolerated and completely degraded carbofuran phenol at initial concentrations of 20 and 30 mM and also higher. Such a bacterial strain could be used for bioremediation of environments contaminated with phenolic compounds.     

Effects of One and Two Applications of Nematicides on Nematode Populations and Soybean Yields

Yields of ''McNair 800'' soybeans, Glycine max (L.) Merr., were significantly increased with ethylene dibromide + chloropicrin, DBCP, phenamiphos, and aldicarb applied at-planting and with phenamiphos, aldicarb, and DBCP applied postplant to soil infested with Meloidogyne incognita (Kofoid and White) Chitwood. Yields of ''GaSoy 17'' were significantly increased with ethylene dibromide + chloropicrin, DBCP, phenamiphos, and aldicarb applied, preplant and with DBCP, carbofuran, phenamiphos, aldicarb, and DBCP applied postplant to soil infested with Hoplolaimus columbus Sher. In several instances, preplant or at-planting treatments plus postplant treatments with the same or different chemicals were more effective than either treatment alone. Generally, the fumigants were more effective than the nonfumigants when they were applied at-planting to M. incognita-infested soil and preplant to H. columbus-infested soil. Phenamiphos, aldicarb, and DBCP were about equally effective when they were applied postplant in M. incognita-infested soil, but DBCP was more effective than carbofuran. Carbofuran, phenamiphos, aldicarb, and DBCP were about equally effective when applied postplant to H. columbus-infested soil.     

Bioaugmentation of carbofuran residues in soil by Burkholderia cepacia PCL3: A small-scale field study

A small-scale field study was conducted in 1 m × 1.25 m × 20 cm plots. In the soil with only indigenous microorganisms, carbofuran degradation was slow with a long half-life (t_1/2) of 127 d. Bioaugmenting the soil with the immobilized PCL3 could shorten the t_1/2 of carbofuran to 16 d. The t_1/2 rose to a significantly longer 28 d when the free cells of PCL3 were used instead of the immobilized cells. Viable cell counting of carbofuran degraders in soil indicated that the carbofuran degradation efficiency directly correlated to the number of introduced carbofuran degraders that survived in the system. PCL3 in free-cell form did not survive in the soil during the field operation; this suggested that the immobilization of PCL3 is needed in order to implement the bioaugmentation technique in a real environment.     

Purification and characterization of the N-methylcarbamate hydrolase from Pseudomonas strain CRL-OK.

A unique cytosolic enzyme that hydrolyzes the carbamate linkage of the insecticide carbaryl (1-naphthyl N-methylcarbamate) was purified from extracts of Pseudomonas sp. strain CRL-OK. Substrates of the hydrolase include the N-methylcarbamate pesticides carbofuran and aldicarb but not the phenylcarbamate isopropyl m-chlorocarbanilate, the thiocarbamate S-ethyl N,N-dipropylthiocarbamate, or the dimethylcarbamate o-nitrophenyldimethylcarbamate.     

Purification and characterization of the N-methylcarbamate hydrolase from Pseudomonas strain CRL-OK.

A unique cytosolic enzyme that hydrolyzes the carbamate linkage of the insecticide carbaryl (1-naphthyl N-methylcarbamate) was purified from extracts of Pseudomonas sp. strain CRL-OK. Substrates of the hydrolase include the N-methylcarbamate pesticides carbofuran and aldicarb but not the phenylcarbamate isopropyl m-chlorocarbanilate, the thiocarbamate S-ethyl N,N-dipropylthiocarbamate, or the dimethylcarbamate o-nitrophenyldimethylcarbamate.     

Effect of GA3 on the Phytotoxicity of Aldicarb and Carbofuran on Seedling Growth in Capsicum frutescens var. California Wonder and Rate of Root Knot Nematode Infestation

The present investigation dealt with the effect of the two granular systemic nematicides aldicarb and carbofuran, individually and in combination with 100 mg · 1^-1 GA₃, on plant growth and root knot formation in C. frutescens var. California Wonder. Both nematicides and GA₃ were applied as a seed-dip treatment. GA₃ increased seed germination and seedling growth. All concentrations (2 to 20 g a.i. · 1^-1) of aldicarb and carbofuran, when applied independently, reduced seed germination and length of epicotyl and hypocotyl. However, application of these nematicides in combination with 100 mg · 1^-1 GA₃ showed antagonistic behaviour. All the treated seedlings were inoculated with 1000 nematode larvae of Meloidogyne incognita. Vegetative parameters of the plant were studied 15 days after transplantation. A combination of GA₃ (100 mg · 1^-1) with different concentrations of nematicides showed a synergistic effect on treated plants. Root knot index in plants treated with nematicides was found to be reduced with increasing concentrations of both nematicides. Maximum reduction in root knot index was observed at highest dose (20 g a.i. · 1^-1) of both nematicides, when applied in combination with 100 mg · 1^-1 GA₃. Proteolytic activities were decreased in plants treated with both aldicarb and carbofuran. Supplementation of the nematicides with GA₃ resulted in an increase in enzyme activities of the treated plants. Toxic residues increased with increasing concentration of both nematicides, whereas it was reduced at highest concentration of both nematicides when applied in combination with GA₃.     

Effects of Selected Carbamate and Organophosphate Nematicides on Hatching and Emergence of Heterodera schachtii

Ethoprop, oxamyl, PP 156, fenamiphos, carbofuran , AC 64,475, Bunema M®, CG 12223, aldicarb, aldicarbsulfoxide, and aldicarbsulfone were tested for their effects on hatching and emergence of larvae from cysts of Heterodera schachtii. The oxime carbamates and carbofuran inhibited hatching , but this response was reversed by removing the chemical treatment . Inhibition of hatching by Bunema M and all organophosphates tested was irreversible .     

Chemical control of stem nematode, Ditylenchus dipsaci, in field beans (Vicia faba)

‘Giant race’ stem nematode (Ditylenchus dipsaci) was well controlled in spring beans (Vicia faba) by up to 5 kg aldicarb or carbofuran ha^-1 applied to the seed furrows at sowing. Carbofuran was rather more effective in the clay loam soil used than was aldicarb. The best treatments almost eliminated injury to the stems and nematode infestation in the harvested seed. Similarly applied, oxamyl and fenamiphos were less effective and phorate, dimethoate and disulfoton were ineffective. Applying part of the dosage of an effective nematicide to the seed furrows and part along the plant rows mid-season was no more effective and was sometimes less effective than applying the whole dose to the seed furrows. Treating the plant rows mid-season with aldicarb or phoxim sometimes enhanced control but thiabendazole applied thus did not. Seed furrow applications of aldicarb or carbofuran were much less effective in controlling the nematodes in winter beans and seed dressings were less effective than seed furrow treatments. In one experiment, in plots in which aldicarb or oxamyl had been applied to the seed furrows, phoxim or thiabendazole applied over the rows of plants, enhanced nematode control. In two other experiments, thiabendazole was ineffective when applied in this way or when applied as a combined soil and plant treatment.     

Movement and distribution pattern of the residues of granular insecticides in tropical soil and okra plants

Summary The increased downward mobility of phorate, quinalphos and carbofuran residues was detected in soil with increase in depth of soil column whereas aldicarb was found to remain localised mainly in 0–7.5 cm and 7.5–15.0 cm layers. Persistence of organophosphate insecticides was higher as compared to carbamates in all the soil layers. Residues of all the four insecticides got distributed in all parts of okra plant through uptake but accumulated in higher amounts in fruits only. Contribution No. 312/83 from I.I.H.R. Bangalore (India)     

Production of biosurfactant on crude date syrup under saline conditions by entrapped cells of Natrialba sp. strain E21, an extremely halophilic bacterium isolated from a solar saltern (Ain Salah, Algeria)

A bacterial strain E21 was isolated from a sample of water collected in the salt lake located close to Ain Salah, Algeria. The analysis of 16S rRNA gene sequence had indicated that the strain had 93 % sequence similarity with the genus Natrialba sp. strain E21 (GenBank, FR750525.1) and was considered extremely halophilic. Production of biosurfactant by the strain E21 with free and entrapped cells was investigated using soluble starch in the saline conditions. Biosurfactant synthesis was followed by measuring the surface tension and emulsifying index 9 days under optimal conditions (40 °C, pH 7). Some diffusional limitations in alginate and agar beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture. The minimum values of surface tension were 27 and 30 mN m^?1 achieved after 9 days with free and immobilized cells, respectively, while the corresponding maximum E24 values were 65.3 and 62.3 %, respectively. The re-use of bacterial cells along with the limited cell losses provided by the immobilized system might lead to significant reduction of the biosurfactant production cost.     

The relative efficiency of foliar sprays and granular insecticides in control of the jassid Empoasca lybica on eggplant

Omethoate, formothion, monocrotophos and carbaryl were the most effective of a number of insecticides evaluated as foliar sprays for the control of Empoasca lybica on eggplant. The duration of insecticidal activity was about 20 days, three sprays being required during the season. Disulfoton, carbofuran and terbufos granules applied to the soil at the rate of 0.1 g a.i./plant c. 1 month after transplanting gave control of jassid throughout the season and a significant yield response.     

Production of Ricinoleic Acid from Castor Oil by Immobilised Lipases

Abstract

Porcine pancreatic lipase (PPL), Candida rugosa lipase (CRL), and Castor bean lipase (CBL) were immobilized on celite by deposition from aqueous solution by the addition of hexane. Lipolytic performance of free and immobilized lipases were compared and optimizations of lipolytic enzymatic reactions conditions were performed by free and immobilized derivatives using olive oil as substrate. Afterwards, the influence on lipolysis of castor oil of free lipases and immobilized lipase derivatives have been studied in the case of production of ricinoleic acid. All of the lipases performances were compared and enzyme derivative was selected to be very effective on the production of ricinoleic acid by lipolysis reaction. Various reaction parameters affecting the production of ricinoleic acid were investigated with selected the enzyme derivative.

The maximum ricinoleic acid yield was observed at pH 7–8, 50°C, for 3 hours of reaction period with immobilized 1,3-specific PPL on celite. The kinetic constants K_m and V_max were calculated as 1.6 × 10^?4 mM and 22.2 mM from a Lineweaver–Burk plot with the same enzyme derivative. To investigate the operational stability of the lipase, the three step lipolysis process was repeated by transferring the immobilized lipase to a substrate mixture. As a result, the percentange of conversion after usage decreased markedly.     

Effects of dietary crude protein and tannic acid on rumen fermentation,rumen microbiota and nutrient digestion in beef cattle

The objectives of the trial were to study the effects of dietary crude protein (CP) and tannic acid (TA) on rumen fermentation, microbiota and nutrient digestion in beef cattle. Eight growing beef cattle (live weight 350 ± 25 kg) were allocated in a 2 × 2 crossover design using two levels of dietary CP [111 g/kg dry matter (DM) and 136 g/kg DM] and two levels of TA (0 and 16.9 g/kg DM) as experimental treatments. Each experimental period lasted 19 d, consisting of 14-d adaptation and 5-d sampling. The impacts of dietary CP and TA on ruminal microbiota were analysed using high-throughput sequencing of 16S rRNA gene. Results indicated that no interactions between dietary CP and TA were found on rumen fermentation and nutrient digestibility. Increasing dietary CP level from 111 to 136 g/kg DM increased the ruminal concentrations of ammonia nitrogen (NH₃-N) (p < 0.01) and improved the CP digestibility (p < 0.001). Adding TA at 16.9 g/kg DM inhibited rumen fermentation and decreased the digestibility of dietary CP (p < 0.001), DM (p < 0.05) and organic matter (p < 0.01). Increasing the dietary CP level or adding TA did not affect the relative abundances of the major bacteria Firmicutes and Proteobacteria at the phylum level and Prevotella_1 and Christensenellaceae_R-7_group at the genus level, even though adding TA increased the Shannon index of the ruminal bacterial community. TA was partly hydrolysed to pyrogallol, gallic acid and resorcinol in rumen fluid and the inhibitory effects of TA on rumen fermentation and nutrient digestibility could have been resulted from the TA metabolites including pyrogallol, gallic acid and resorcinol as well as the protein-binding effect.     

Biodegradation of Carbaryl by a Micrococcus Species

A bacterium capable of utilizing carbaryl as sole source of carbon was isolated from garden soil and identified as a Micrococcus species. The organism also utilized carbofuran, naphthalene, 1-naphthol, and several other aromatic compounds as growth substrates. The organism degraded carbaryl by hydrolysis to yield 1-naphthol and methylamine. 1-Naphthol was further metabolized via salicylate by a gentisate pathway, as evidenced by oxygen uptake and enzymatic studies. Received: 27 November 2000 / Accepted: 29 December 2000     

Production of cyclodextrin glycosyltransferase by immobilized <Emphasis Type="Italic">Bacillus</Emphasis> sp. on chitosan matrix

The whole-cell immobilization on chitosan matrix was evaluated. Bacillus sp., as producer of CGTase, was grown in solid-state and batch cultivation using three types of starches (cassava, potato and cornstarch). Biomass growth and substrate consumption were assessed by flow cytometry and modified phenol–sulfuric acid assays, respectively. Qualitative analysis of CGTase production was determined by colorless area formation on solid culture containing phenolphthalein. Scanning electron microscopy (SEM) analysis demonstrated that bacterial cells were immobilized on chitosan matrix efficiently. Free cells reached very high numbers during batch culture while immobilized cells maintained initial inoculum concentration. The maximum enzyme activity achieved by free cells was 58.15 U ml^?1 (36 h), 47.50 U ml^?1 (36 h) and 68.36 U ml^?1 (36 h) on cassava, potato and cornstarch, respectively. CGTase activities for immobilized cells were 82.15 U ml^?1 (18 h) on cassava, 79.17 U ml^?1 (12 h) on potato and 55.37 U ml^?1 (in 6 h and max 77.75 U ml^?1 in 36 h) on cornstarch. Application of immobilization technique increased CGTase activity significantly. The immobilized cells produced CGTase with higher activity in a shorter fermentation time comparing to free cells.     

Mutagenic and cytotoxic activities of benfuracarb insecticide

Benfuracarb is a carbamate insecticide used to control insect pests in vegetables and it has anti-acetylcholinesterase activity lower than other carbamates. Cytotoxic effects of benfuracarb were evaluated by using root growth inhibition (EC₅₀), mitotic index (MI), and mitotic phase determinations on the root meristem cells of Allium cepa and mutagenic effects were determined in Salmonella typhymurium Ames test by TA98 and TA100 strains with and without metabolic activation. In Allium test, 1 % DMSO was used as negative control group and 10 ppm MMS was used as positive control group. 75 ppm concentration of benfuracarb was found as EC₅₀. In MI and mitotic phases determination study, 37.5, 75 and 150 ppm doses of benfuracarb were used. Dose-dependent cytotoxic activity was found by root growth inhibition and MI studies. It was identified that mitotic inhibition activity of benfuracarb was higher than 10 ppm MMS. In Ames test, mutagenic activity was not observed and over 200 µg/plate of benfuracarb was determined as cytotoxic to S. typhymurium strains. Benfuracarb can be called as “mitotic inhibitor” but not called as mutagen.     

Immobilization and Characterization of a Thermostable Lipase

Lipases have found a number of commercial applications. However, thermostable lipase immobilized on nanoparticle is not extensively characterized. In this study, a recombinant thermostable lipase (designated as TtL) from Thermus thermophilus WL was expressed in Escherichia coli and immobilized onto 3-APTES-modified Fe₃O₄@SiO₂ supermagnetic nanoparticles. Based on analyses with tricine–sodium dodecyl sulfate–polyacrylamide gel electrophoresis, X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer observation, the diameter of immobilized lipase nanoparticle was 18.4 (±2.4)?nm, and its saturation magnetization value was 52.3 emu/g. The immobilized lipase could be separated from the reaction medium rapidly and easily in a magnetic field. The biochemical characterizations revealed that, comparing with the free one, the immobilized lipase exhibited better resistance to temperature, pH, metal ions, enzyme inhibitors, and detergents. The K _m value for the immobilized TtL (2.56 mg/mL) was found to be lower than that of the free one (3.74 mg/mL), showing that the immobilization improved the affinity of lipase for its substrate. In addition, the immobilized TtL exhibited good reusability. It retained more than 79.5 % of its initial activity after reusing for 10 cycles. Therefore, our study presented that the possibility of the efficient reuse of the thermostable lipase immobilized on supermagnetic nanoparticles made it attractive from the viewpoint of practical application.