Biodegradation of 2,4-dichlorophenoxyacetic acid and 4-chlorophenol in contaminated soils by Pseudomonas fluorescens strain HH

Herbicides with 2,4-dichlorophenoxyacetic acid (2,4D) has been commonly used to control weeds and widely detected in environments. In this study, biodegradating activity of Pseudomonas fluorescens HH on 2,4D and 4-chlorophenol (4CP) in soil was carried out. The inoculation with Pseudomonas fluorescens HH in soils increased the degradation of 4CP and 2,4D by from 47.0% to 51.4% and from 38.4% to 47.4%, respectively, compared to the degradation by autochthonous microorganisms. Pseudomonas fluorescens HH could degrade well 2,4D and 4CP in various soils, but the most efficient chemical removal was observed when they were in the loamy soil. Moreover, the efficiency of chemical degradation was significantly affected by the moisture contents with the highest performance of degradation at 10 and 20% soil moisture. Also, the addition of nitrogen (N), phosphorous (P) and potassium (K) stimulated the dissipation rates. The determination of degradation pathway for 2,4D in Pseudomonas fluorescens HH indicated that 2,4-dichlorophenol (2,4DCP) and 4CP were formed as metabolites

Effects of nutrients and environmental conditions on thiobencarb degradation by a mixed culture of Pseudomonas sp. Th1 and Cupriavidus oxalaticus Th2

Thiobencarb is an herbicide component extensively applied for weed control. In this study, the mixed culture of Pseudomonas sp. Th1 and Cupriavidus oxalaticus Th2 was determined for degradability towards thiobencarb at several conditions. The degradation of thiobencarb at 50 µM by the mixture of these strains in the medium without any co-substrate was 48.5±5.5% for 24 hours, increased to 78.0% with the addition of 0.5 mg/L ammonium sulfate and 0.5 mg/L succinate in to the medium. Moreover, the mixed culture could degrade the compound at quite ranges of NaCl concentrations, pH and temperatures. To increase the degradation of the compound in a commercial herbicide, bacteria were immobilized in a matrix consisting of polyvinyl alcohol and sodium alginate. The average degradation of thiobencarb in an herbicide named Satunil 60E by immobilized bacteria was 25.8% higher than that of non-immobilized bacteria at a cell density of 1.0×107 CFUs/mL

Depth-dose distribution in potatoes with low-energy X-rays

Irradiation is known as a handful measure to inhibit potato sprouting, kill harmful bacteria, and increase preservation. The absorbed dose is one of the essential characteristics of the irradiation process. In this study, the depth-dose distributions in potatoes and polymethyl methacrylate were investigated under low-energy X-ray irradiation by using the Fricke dosimeter and Gafchromic film dosimeter. The dose rates required for the rays to penetrate in polymethyl methacrylate were compared with those in potatoes. Polymethyl methacrylate could be used as a phantom in measuring the depth dose delivered in potatoes. The difference in depth-dose distribution in potatoes between one-sided and double-sided irradiation was also investigated. The calculated dose uniformity ratio values are 5.8 and 1.9 for potatoes irradiating one-sided and double-sided

Enhanced Adsorption of Methylene Blue by Chemically Modified Materials Derived from Phragmites australis Stems

In this study, the biomass of Phragmites australis was chemically modified using NaOH and subsequently citric acid to produce an effective adsorbent named SA-RPB. The absorbent was characterized using XRD, SEM, BET, and FT-IR methods. The study's findings indicated that the adsorbent existed mainly as cellulose crystals, contained micropores with an average diameter of 15.97 nm, and had a large number of hydroxyl and carboxyl groups on the surface. The adsorption process of SA-RPB was evaluated through the adsorption of methylene blue (MB) dye in aqueous solution. Adsorption kinetics showed that the pseudo-second-order model well described the adsorption process. The adsorption isotherm process satisfactorily fitted with the Langmuir model with the maximum adsorption capacity of 191.49 mg/g at 303 K. These findings show that MB may be efficiently removed from aqueous solutions using the adsorbent made from the raw biomass of Phragmites australis treated with NaOH and then citric acid

Degradation of leaves and cellulose by Bacillus subtilis CL3 and Pseudomonas aeruginosa CL5 isolated from left waste dumps in Vietnam

The biodegradation capacity of two bacterial strains, Bacillus subtilis CL3 and Pseudomonas aeruginosa CL5, isolated from left waste dumps on thee different plant leaves were investigated. The leaves were derived from perennial plants, Malabar almond tree (Terminalia catappa), eucalyptus (Eucalyptus terticornis) and African mahogany (Khaya senegalensis). Among those 3 plants, Eucalyptus terticornis is known to be resistant for biodegradation in nature. In our study, B. subtilis CL3 could degrade a half of Eucalyptus terticornis leaves within 10 days. On the other hand, P. aeruginosa CL5 showed relatively poor degradation rate of the leaves of Eucalyptus terticornis, but could effectively degrade Khaya senegalensis and Terminalia catappa leaves than B. subtilis CL3. When these two bacteria strains were mixed, the degradation rates of all these types of leaves were enhanced. While B. subtilis CL3 could utilize 1,8-cineole, a component extracted from Eucalyptus terticornis, as a sole carbon source, this component inhibited the growth of P. aeruginosa CL5. The multiple and efficient left degradation capacities make these isolates good candidates for bioremediation of leaf waste and cellulose. Citation: Ha Danh Duc, 2017. Degradation of leaves and cellulose by Bacillus subtilis CL3 and Pseudomonas aeruginosa CL5 isolated from left waste dumps in Vietnam. Tap chi Sinh hoc, 39(4): 483-488. DOI: 10.15625/0866-7160/v39n4.10744.*Corresponding author: [email protected] 5 December 2016, accepted 12 December 2017

Treatment of wastewater from intensive striped catfish farming using Hymenachne acutigluma in batch surface-constructed wetland

Intensive striped catfish (Pangasianodon hypophthalmus) farming has recently expanded owing to its economic benefits but it has led to severe aquatic pollution. In this study, a batch surface-constructed wetland system cultivated with Hymenachne acutigluma grass was designed to treat wastewater collected from catfish ponds. The planted wetland system showed effective operation, as 81.7% of NO-3-N, 63.6% of NH+4-N, and 77.5% of PO3-4-P (w/w) in the wastewater were removed over four months. Besides, the wetland significantly decreased the chemical oxygen demand and total suspended solids from the wastewater. The absorption by the grass resulted in the removal of 20.3 and 22.2% of the total nitrogen (N) and phosphorus (P) from wastewater, respectively. The determination of the nutrient mass balance in the planted system showed that phosphorus in the wastewater was mainly removed through sediment deposition, while a large amount of nitrogen was not lost because of the sediment deposition and plant uptake. Moreover, H. acutigluma cultured in the system can serve as food for cattle. This study shows an ecofriendly approach for the effective remediation of wastewater obtained from the farming of intensive striped catfish

Chemical composition, enzyme inhibitory activities, and molecular docking studies of essential oil of <i>Knema globularia</i> leaves from Vietnam

In the present work, chemical composition, enzyme inhibitory activities, and molecular docking studies of essential oil (EO) of Knema globularia leaves collected from Vinh Phuc Province, Vietnam, were investigated. The EO from the leaves of K. globularia was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC-MS) analysis. The leaf EO yield was 0.14 ± 0.01% (w/w), comprising 39 identified components, constituting 96.77% of the EO content. Notable constituents included β-caryophyllene (54.11%), α-humulene (12.67%), and (E)-β-ocimene (8.82%). Enzyme inhibitions were assessed via the α-amylase inhibitory assay (IC50 = 282.71 ± 10.06 μg/mL) and tyrosinase inhibitory assay (IC50 = 993.92 ± 37.40 μg/mL). The molecular docking method has been employed to observe valuable binding interactions and binding energy with the main compounds on the target enzymes α-amylase and tyrosinase. Caryophyllene oxide exhibits the strongest affinity with α-amylase among the other major compounds. Meanwhile, viridiflorene shows the best binding energy with the tyrosinase enzyme. This is the first study providing valuable scientific data on the in vitro inhibitory activities of α-amylase and tyrosinase enzymes of the leaf EO of K. globularia and evaluating its main compounds through a molecular docking approach on these enzyme targets.</p