Lindane uptake and degradation by aquatic Streptomyces sp. strain M7

Five actinomycete strains isolated from pesticide-contaminated sediments were able to grow in the presence of 10 μg l⁻¹ lindane, an organochlorine pesticide. The strain growing best in the presence of lindane as the only carbon source was identified as Streptomyces sp. M7. After 96 h of incubation in synthetic medium containing lindane and glucose, both substrates were simultaneously consumed; glucose 6.0 g l⁻¹ improved lindane degradation and obtained biomass. When Streptomyces sp. M7 was cultured in presence of lindane plus glucose, the disappearance of the pesticide from the medium and the lindane degradation was observed after 72 h of incubation. This is the first report of lindane degradation without intracellular accumulation or biotransformation products of lindane using Streptomyces sp. under aerobic conditions.Relevance to industryThis is the first report of lindane removal without intracellular accumulation or biotransformation products of lindane using Streptomyces sp. strain M7, an actinomycete isolated from pesticide-contaminated sediments from Tucuman, Argentina.     

Characteristics of γ-hexachlorocyclohexane biodegradation by a nitrogen-fixing cyanobacterium, Anabaena azotica

Biodegradation of γ-hexachlorocyclohexane (lindane) by a nitrogen-fixing cyanobacterium isolated from Chinese paddy soils, Anabaena azotica 118, was investigated. Lindane with an initial concentration of 0.2 mg L⁻¹ in the cultures had no negative effect on the chlorophyll a concentration of A. azotica after 5 d exposure. The tolerance of this cyanobacterium to lindane indicates that it has the potential to biodegrade lindane. The degradation experiments show that the percentage of lindane removal efficiency by A. azotica was 48.8% after 5 d, at an initial lindane concentration of 0.2 mg L⁻¹ and initial A. azotica chlorophyll a concentration of 50 mg L⁻¹. The calculated half-life was 4.78 d. Elevated culture temperature, irradiation, and usage of nitrate as the nitrogen source in the cultures could increase the biodegradation efficiency of lindane. γ-Pentachlorocyclohexene was detected as a metabolite of lindane. The ability of A. azotica to biodegrade lindane has potential use in the bioremediation for this organochlorine pesticide.     

Phenanthrene biodegradation by immobilized microbial consortium in polyvinyl alcohol cryogel beads

Removal of polycyclic aromatic hydrocarbons (PAHs), a group of widespread toxic compounds, has been one of the environmental issues in wastewater treatment systems for many years. In this study, biodegradation of phenanthrene (PHE), as a model contaminant, by a microbial consortium entrapped in polyvinyl alcohol (PVA) cryogel prepared by freeze-thaw method was investigated. The effect of inoculum size (300–900 mg of cell dry weight per liter) and initial PHE concentration (100–2000 ppm) as well as bead cell density (5 and 10 mg ml⁻¹) on PHE biodegradation by freely suspended cell (FC) and immobilized cell (IC) systems in aqueous phase was examined. Results showed that although both IC and FC systems were capable of complete removal of 100 and 250 ppm of initial PHE (as sole carbon and energy sources), incomplete PHE removals were observed at higher initial PHE concentrations up to 2000 ppm after 7 days. IC system resulted in the maximum PHE removal of 400 ppm at initial PHE concentration of 750 ppm and inoculum size of 600 mg l⁻¹, while under these conditions FC system removed 310 ppm of PHE. Moreover, bead cell density was shown to affect the performance of IC system, with the lower density of 5 mg ml⁻¹ leading to a higher PHE removal due to the enhanced transport phenomena in the culture. Additionally, a correlation was proposed to predict PHE biodegradation at a range of initial PHE concentrations.     

Optimization of environmental parameters for biodegradation of alpha and beta endosulfan in soil slurry by Pseudomonas aeruginosa

Aim: To determine optimal environmental conditions for achieving biodegradation of α‐ and β‐endosulfan in soil slurries following inoculation with an endosulfan degrading strain of Pseudomonas aeruginosa. Methods and Results: Parameters that were investigated included soil texture, soil slurry: water ratios, initial inoculum size, pH, incubation temperature, aeration, and the use of exogenous sources of organic and amino acids. The results showed that endosulfan degradation was most effectively achieved at an initial inoculum size of 600 μl (OD = 0·86), incubation temperature of 30°C, in aerated slurries at pH 8, in loam soil. Under these conditions, the bacterium removed more than 85% of spiked α‐ and β‐endosulfan (100 mg l^?1) after 16 days. Abiotic degradation in noninoculated control medium within same incubation period was about 16%. Biodegradation of endosulfan varied in different textured soils, being more rapid in course textured soil than in fine textured soil. Increasing the soil contents in the slurry above 15% resulted in less biodegradation of endosulfan. Exogenous application of organic acids (citric acid and acetic acid) and amino acids (l ‐methionine and l ‐cystein) had stimulatory and inhibitory effects, respectively, on biodegradation of endosulfan. Conclusion: The results of this study demonstrated that biodegradation of endosulfan by Ps. aeruginosa in soil sediments enhanced significantly under optimized environmental conditions. Significance and Impact of the Study: Endosulfan is a commonly used pesticide that can contaminate soil, wetlands and groundwater. Our study demonstrates that bioaugmentation of contaminated soils with an endosulfan degrading bacterium under optimized conditions provides an effective bioremediation strategy.     

Biodegradation of lindane pesticide by non white- rots soil fungus <Emphasis Type="Italic">Fusarium</Emphasis> sp.

Lindane or γ- hexachlorocyclohexane (γ-HCH) is a chlorinated pesticide and its toxic effects on biota necessitate its removal. Microbial degradation is an important process for pesticide bioremediation and the role of soil fungi in recycling of organic matter prompted us to study the biodegradation of lindane using fungi. This study aims at enrichment, isolation and screening of soil fungi capable of metabolizing lindane. Two Fusarium species (F. poae and F. solani) isolated from the pesticide contaminated soil showed better growth on the plates supplemented with lindane as a sole carbon source, when compared with the growth performance of other fungal isolates from the same contaminated soil. However, ANOVA revealed a significant difference in fungal biomass production in both F. poae (F = 22.02; N = 15; P < 0.001) and F. solani (F = 268.75; N = 15; P < 0.001) across different lindane concentrations (0–600 μg ml⁻¹). Growth of both Fusarium sp. was maximum at a lindane concentration of 100 μg ml⁻¹, while minimum at 600 μg ml⁻¹ concentrations. Results on the time dependent release of chlorine by the Fusarium strains in the presence of various concentration of lindane showed the highest mineralization of the pesticide on 10th day of incubation. Time dependent variations in the release of chlorine from 1st to 10th day by both the selected fungal strains were found to be statistically significant. A significant positive relationship exists between fungal biomass increase and chlorine release existed for both F. solani (R2 = 0.960) and F. poae (R2 = 0.628). The results of gas chromatograph analysis of γ- HCH confirmed the biodegradation and utilization of γ- HCH by F. poae and F. solani. The data on lindane degradation by the two fungal strains demonstrated that the biodegradation of lindane by F. solani (59.4%) was slightly higher than that by the F. poae (56.7%).     

An efficient callus-based in vitro regeneration protocol for Warburgia Ugandensis Sprague,an important medicinal plant in Africa

Warburgia ugandensis Sprague is a woody species in the family Canellaceae and an important source of medicines in Africa. Natural propagation of W. ugandensis is problematic due to its recalcitrant seeds and lack of an efficient in vitro regeneration system for this species. This study describes an efficient regeneration protocol. Petiole bases and shoot tips were used as explants. Callus tissue developed when the explants were cultured on Murashige and Skoog medium containing 30 g L⁻¹ sucrose and 7 g L⁻¹ agar (MS30 medium), supplemented with 1.0 mg L⁻¹ indole-3-butyric acid (IBA), 1.6 mg L⁻¹ 6-benzylaminopurine (BA), and 0.1 mg L⁻¹ thidiazuron (TDZ). Adventitious buds were efficiently induced from the callus when the MS30 medium was supplemented with 0.8 mg L⁻¹ BA and 0.2 mg L⁻¹ IBA. Root induction occurred within 7–10 d on half-strength MS30 medium supplemented with 0.8–1.0 mg L⁻¹ 1-napthalene acetic acid (NAA), 0.2 mg L⁻¹ IBA, and 0.03% (w/v) activated charcoal (AC). Roots were followed by root elongation on the same medium but lacking NAA and IBA. Approximately 50% of the plantlets cultured produced roots, while more than 80% of the plantlets survived and successfully grew to maturity.

     

Studies revealing bioremediation potential of the strain Burkholderia sp. GB-01 for abamectin contaminated soils

Burkholderia sp. GB-01 strain was used to study different factors affecting its growth for inoculum production and then evaluated for abamectin degradation in soil for optimization under various conditions. The efficiency of abamectin degradation in soil by strain GB-01 was seen to be dependent on soil pH, temperature, initial abamectin concentration, and inoculum size along with inoculation frequency. Induction studies showed that abamectin depletion was faster when degrading cells were induced by pre-exposure to abamectin. Experiments performed with varying concentrations (2–160 mg Kg⁻¹) of abamectin-spiked soils showed that strain GB-01 could effectively degrade abamectin over the range of 2–40 mg Kg⁻¹. The doses used were higher than the recommended dose for an agricultural application of abamectin, taking in account the over-use or spill situations. A cell density of approximately 10⁸ viable cells g⁻¹ dry weight of soil was found to be suitable for bioremediation over a temperature range of 30–35°C and soil pH 7.5–8.5. This is the first report on bacterial degradation of abamectin in soil by a Burkholderia species, and our results indicated that this bacterium may be useful for efficient removal of abamectin from contaminated soils.     

Effective biodegradation of 2,4,6-trinitrotoluene using a novel bacterial strain isolated from TNT-contaminated soil

In this environmental-sample based study, rapid microbial-mediated degradation of 2,4,6-trinitrotoluene (TNT) contaminated soils is demonstrated by a novel strain, Achromobacter spanius STE 11. Complete removal of 100 mg L⁻¹ TNT is achieved within only 20 h under aerobic conditions by the isolate. In this bio-conversion process, TNT is transformed to 2,4-dinitrotoluene (7 mg L⁻¹), 2,6-dinitrotoluene (3 mg L⁻¹), 4-aminodinitrotoluene (49 mg L⁻¹) and 2-aminodinitrotoluene (16 mg L⁻¹) as the key metabolites. A. spanius STE 11 has the ability to denitrate TNT in aerobic conditions as suggested by the dinitrotoluene and NO₃ productions during the growth period. Elemental analysis results indicate that 24.77 mg L⁻¹ nitrogen from TNT was accumulated in the cell biomass, showing that STE 11 can use TNT as its sole nitrogen source. TNT degradation was observed between pH 4.0–8.0 and 4–43 °C; however, the most efficient degradation was at pH 6.0–7.0 and 30 °C.     

Biodegradation of phenol using hairy roots of Helianthus annuus L.

Phenol is a common pollutant which is found in wastewater of many industries and removal of phenol from the industrial effluents is a major challenge. Recently, the use of hairy roots has been probed for the removal of phenol. In the present study, phenol at various concentrations (100–500 mg L⁻¹) was treated with hairy roots of Helianthus annuus (sunflower hairy roots, SHRs). SHRs removed 100 mg L⁻¹ of phenol after 144 h of incubation. The effect of polyethylene glycol (PEG), l-proline and d-glucose on the rate of phenol removal was also studied. l-proline enhanced the removal efficiency of SHRs resulting in the removal of 100 mg L⁻¹ of phenol after 24 h while PEG did not show any effect on removal. Peroxidase activity was induced after 24 h of phenol addition. Phenol metabolism to generate catechol as a major metabolite was confirmed using HPLC and GC–MS analyses. The detection of small amounts of cis-cis muconic acid and fumaric acid in the reaction medium suggests that these metabolites are produced from the ring cleavage of catechol. The phytotoxicity and cytotoxicity results suggest the non-toxic nature of the resulting phenol metabolites.     

Application of soil slurry respirometry to optimise and subsequently monitor ex situ bioremediation of hydrocarbon-contaminated soils

A protocol to monitor respiration as O₂ consumption in soil slurries using the Strathtox^® respirometer was developed and tested on four soils from brownfield sites. Respiration rates (mg l⁻¹ h⁻¹) of soil slurries in the Strathtox^® were compared with rates (μl min⁻¹) of field moist soils analysed using the Columbus Oxymax^® ER10 respirometer. One of the soils (99612B), historically contaminated with diesel, was further studied by monitoring the effect of inorganic NH₄NO₃ liquid nutrient on enhancing respiration rate. Soil microcosms were monitored continuously on the Oxymax^® or sampled at 24, 48 and 72 h intervals, prepared as soil slurries, and analysed on the Strathtox^®. On the full-scale remediation project (∼6000 m³) soil 99612B was treated as a biopile with spent mushroom compost (SMC) amendment and respiration rates monitored in samples over an 8-week period. In the laboratory microcosm experiment and full-scale bioremediation treatment described, correlation was found for respiration rates between the two respirometry systems.     

Simultaneous bioremediation of Cr(VI) and lindane in soil by actinobacteria

Environments co-contaminated with metals and organic compounds are difficult to remediate. Actinobacteria is an important group of microorganisms found in soils, with high metabolic versatility and potential for bioremediation. In this paper, actinobacteria were used to remediate soil co-contaminated with Cr(VI) and lindane. Five actinobacteria, tolerant to Cr(VI) and lindane mixture were selected: Streptomyces spp. A5, A11, M7, and MC1, and Amycolatopsis tucumanensis DSM 45259. Sterilized soil samples were inoculated with actinobacteria strains, either individually or as a consortium, and contaminated with Cr(VI) and lindane, either immediately or after 7 days of growth, and incubated at 30 °C during 14 days. All actinobacteria were able to grow and remove both contaminants, the consortium formed by Streptomyces spp. A5, M7, MC1, and A. tucumanensis showed the highest Cr(VI) removal, while Streptomyces sp. M7 produced the maximum lindane removal. In non-sterile soil samples, Streptomyces sp. M7 and the consortium removed more than 40% of the lindane, while Streptomyces sp. M7 demonstrated the greatest Cr(VI) removal. The most appropriate strategy for bioremediation of Cr(VI) and lindane co-contaminated soils would be the inoculation with Streptomyces sp. M7.     

Investigating the degradation behavior of Cypermethrin (CYP) and Chlorpyrifos (CPP) in peach orchard soils using organic/inorganic amendments

Reducing toxic effects of pesticide residues in agricultural soils through organic amendments is an eco-friendly technique. Cypermethrin (CYP) and Chlorpyrifos (CPP) are widely used pesticides in peach growing orchards in Swat valley of Pakistan. The aim of the current study was to investigate the degradation behavior of CYP and CPP in soil by the application of different combination of organic/inorganic amendments. A total of 36 soil samples were used in the current incubation study which was collected from 4 peach orchards in district Swat, Khyber Pakhtunkhwa (KPK), Pakistan. Different amendments including urea, farm yard manure (FYM) and saprofil were applied alone and in various combinations. The initial concentrations of CYP and CPP in the tested soil was range from 0.94 to 4.8 mg kg⁻¹ and 0.024 to 4.12 to mg kg⁻¹. Soil samples were taken at 5, 15, 30 and 45 days after exposure to different treatments. The extraction of pesticides from soils was done through quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method. Soils amended with urea, FYM and saprofil individually and in combinations significantly reduced the concentrations of CYP and CPP. However, the concentration of CYP (24.6) and CPP (27.0) in soil showed higher reduction through the application of FYM. While the concentrations of CYP and CPP were declined with the 5, 15, 30 and 45 days intervals, however, reduction at day 30 and 45 was faster for CYP (16.7 to 8.46) than CPP (20.2 to 12.3). At day 5 and 15, the CYP (42.5 to 30.7) was slightly lower than CPP (42.9 to 32.7).The highest half-life value (t ½) of CYP was in control treatment (32 days) and the shortest was soil amended with FYM (18.6 days). While the longest half-life value (t ½) of CPP was maximum in control treatment (42 days) and the minimum was in FYM (22 days). Based on our findings, it was concluded that soil application of FYM is recommended for the degradation of CYP and CPP.     

Effects of heavy metals on aerobic denitrification by strain Pseudomonas stutzeri PCN-1

Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67∼6.67 mg L⁻¹ h⁻¹), higher nitrite accumulation (47.3∼99.8 mg L⁻¹), and higher N₂O emission ratios (5∼283 mg L⁻¹/mg L⁻¹). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0∼0.05 mg L⁻¹) was found, and the absence of Cu resulted in massive N₂O emission due to poor synthesis of N₂O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5∼2.5 mg L⁻¹) > Cu(II) (0.5∼5 mg L⁻¹) > Ni(II) (2∼10 mg L⁻¹) > Zn(II) (25∼50 mg L⁻¹). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ≈ cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.

     

Evaluation of a method to measure conjugal transfer of recombinant DNA in soil slurries

Release of recombinant microbes into the environment necessitates an evaluation of their ability to transfer genetic material. The present report evaluates a method to detect conjugal DNA plasmid transfer in soil slurries under various environmental conditions. DonorPseudomonas cepacia containing pR388::Tn1721 andP. cepacia recipient cultures were coincubated in soil slurries containing autoclaved or natural soil and treated with one or more of 14 experimental conditions. Conjugal mating frequency (transconjugants per initial donor) ranged from 4.8×10^–1 to 1.9×10^–7. Highest numbers of transconjugants, 1.5×10⁷ colony forming units/ml soil slurry, were observed following incubation at 35°C with an enriched nutrient supplement added to the soil. Low numbers of transconjugants, 10³ colony forming units/ml soil slurry, were observed when mating pairs were subjected to low nutrient or pH stress even though initial donor and recipient populations were maintained at high levels. This test system provides a simple way to estimate effects of changing environmental factors on plasmid transfer rates and on the survival of recombinant microorganisms. By use of soil collected from sites proposed to receive genetically engineered microorganisms, preliminary risk assessments can be obtained regarding the potential for gene transfer and microorganism survival with this soil slurry test system.     

Sphingobium sp. FB3 degrades a mixture of polycyclic aromatic hydrocarbons

A soil sample collected underneath a sewage pipe of the west side of Yangpu refining factory in Haikou city, Hainan Province, China was inoculated in minimum medium supplemented with fluoranthene. After 8 enrichment cycles, a bacterial consortium (Y12) was obtained through water-silicone oil dual system in the laboratory. The consortium Y12 could degrade a mixture of polycyclic aromatic hydrocarbons (PAHs) including phenanthrene, anthracene, fluoranthene, pyrene and benzo[a]pyrene. The consortium Y12 was repeatedly cultured for more than 40 circles, from which a bacterial strain FB3 was isolated. This strain was identified as a Sphingobium sp. through the 16S rDNA sequence alignment. Strain FB3 could degrade 99 ± 0.4%, 67 ± 2%, 97 ± 3%, 72 ± 8%, and 6 ± 2% (uncorrected degradation percentages) of phenanthrene, anthracene, fluoranthene and pyrene each at level of 100 mg L⁻¹ and benzo[a]pyrene at 10 mg L⁻¹, respectively, in 10 days, which the five PAHs were the sole carbon source as a mixture in minimum medium. The degradation percentages of phenanthrene, anthracene, fluoranthene, pyrene (each at level of 100 mg L⁻¹) and benzo[a]pyrene (10 mg L⁻¹) by consortium Y12 were 99 ± 0.1%, 65 ± 3%, 99 ± 0.3%, 79 ± 1% and 7 ± 6%, respectively, in 10 days. Strain FB3 could degrade those PAHs under a range of pH 5–9, being optimum at pH 7.     

Bioaugmentation of a methyl parathion contaminated soil with Pseudomonas sp. strain WBC-3

Pseudomonas sp. strain WBC-3 utilizes methyl parathion (MP) and para-nitrophenol as the sole source of carbon, nitrogen and energy. In this study, strain WBC-3 was inoculated into lab-scale MP-contaminated soil for bioaugmentation. Accelerated removal of MP was achieved in bioaugmentation treatment compared to non-bioaugmentation treatment, with complete removal of 0.536 mg g⁻¹ dry soil in bioaugmentation treatment within 15 days and without accumulation of toxic intermediates. The analysis of denaturing gradient gel electrophoresis and real-time PCR showed that strain WBC-3 existed stably during the entire bioaugmentation period. Simultaneously, redundancy analysis for evaluating the relationships between the environmental factors and microbial community structure indicated that the indigenous bacterial community structure was significantly influenced by strain WBC-3 inoculation (P = 0.002).     

Investigation of Heavy Metal Level and Mineral Nutrient Status in Widely Used Medicinal Plants’ Leaves in Turkey: Insights into Health Implications

The use of plants in treatments has been as old as humanity and it has preserved its popularity for centuries til now because of their availability, affordability and safeness. However, despite their widespread use, safety and quality issues have been major concerns in the world due to industrial- and anthropogenic-based heavy metal contamination risks. Thus, this study was attempted to analyze the heavy metal levels and mineral nutrient status of widely used medicinal plants in Turkey to have insights about their health implications on humans. The plant concentrations of B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn were analyzed by ICP-OES in the leaves of 44 medical plants purchased from herbal markets of three different districts of Istanbul/Turkey. The measured lowest to highest concentrations were 0.065–79.749 mg kg⁻¹ B, 921.802–12,854.410 mg kg⁻¹ Ca, 0.020–0.558 mg kg⁻¹ Cd, 0.015–4.978 mg kg⁻¹ Cr, 0.042–8.489 mg kg⁻¹ Cu, 34.356–858.446 mg kg⁻¹ Fe, 791.323–15,569.349 mg kg⁻¹ K, 102.236–2837.836 mg kg⁻¹ Mg, 4.915–91.519 mg kg⁻¹ Mn, 10.224–3213.703 mg kg⁻¹ Na, 0.001–5.589 mg kg⁻¹ Ni, 0.003–3.636 mg kg⁻¹ Pb and 2.601–36.102 mg kg⁻¹ Zn. Those levels in plants were in acceptable limits though some elements in some plants have high limits which were not harmful. Variations (above acceptable limits) in element concentrations also indicated that these plants could be contaminated with other metals and that genetic variations may influence accumulation of these elements at different contents. Overall, analyzed medicinal plants are expected not to pose any serious threat to human health.

     

Bioremediation of PAH-contaminated soil with fungi – From laboratory to field scale

The purpose of this study was to develop a fungal bioremediation method that could be used for soils heavily contaminated with persistent organic compounds, such as polyaromatic hydrocarbons (PAHs). Sawmill soil, contaminated with PAHs, was mixed with composted green waste (1:1) and incubated with or without fungal inoculum. The treatments were performed at the laboratory and field scales. In the laboratory scale treatment (starting concentration 3500 mg kg⁻¹, sum of 16 PAH) the high molecular weight PAHs were degraded significantly more in the fungal-inoculated microcosms than in the uninoculated ones. In the microcosms inoculated with Phanerochaete velutina, 96% of 4-ring PAHs and 39% of 5- and 6-ring PAHs were removed in three months. In the uninoculated microcosms, 55% of 4-ring PAHs and only 7% of 5- and 6-ring PAHs were degraded. However, during the field scale (2 t) experiment at lower starting concentration (1400 mg kg⁻¹, sum of 16 PAH) the % degradation was similar in both the P. velutina-inoculated and the uninoculated treatments: 94% of the 16 PAHs were degraded in three months. In the field scale experiment the copy number of gram-positive bacteria PAH-ring hydroxylating dioxygenase genes was found to increase 1000 fold, indicating that bacterial PAH degradation also played an important role.     

A microcosm study on bioremediation of fenitrothion-contaminated soil using Burkholderia sp. FDS-1

Fenitrothion, a toxic organophosphorus pesticide, can build up the concentration of nitrophenolic compound in soils and hence needs to be removed. Burkholderia sp. FDS-1, a fenitrothion-degrading strain, was used in this work to study factors affecting its growth, and then evaluated for its capacity to degrade fenitrothion in soil microcosms. Minimal salt medium containing 1% (w/v) glucose was found to be a suitable carbon source for inoculum preparation. Various factors, including soil pH, temperature, initial fenitrothion concentration, and inoculum size influenced the degradation of fenitrothion. Microcosm studies performed with varying concentrations (1–200 mg kg⁻¹) of fenitrothion-spiked soils showed that strain FDS-1 could effectively degrade fenitrothion in the range of 1–50 mg kg⁻¹ soil. The addition of Burkholderia sp. FDS-1 at 2×10⁶ colony forming units g⁻¹ soil was found to be suitable for fenitrothion degradation over a temperature range of 20–40 °C and at a slight alkaline pH (7.5). The results indicate that strain FDS-1 has potential for use in bioremediation of fenitrothion and its metabolite-contaminated sites. This is a model study that could be used for decontamination of sites contaminated with other compounds.     

Cellulolytic enzyme production from agricultural residues for biofuel purpose on circular economy approach

This study evaluated the production of cellulolytic enzymes from different agricultural residues. The crude enzyme extract produced was characterized and applied for saccharification of some agricultural residues. Maximum cellulolytic activities were obtained using soybean hulls. All enzymatic activities were highly stable at 40 °C at a pH range of 4.5–5.5. For stability at low temperatures, the enzyme extract was stored at freezing temperature and cooling for about 290 days without major loss of activity. The K_m values found for total cellulase (FPase), endoglucanase (CMCase), and xylanase were 19.73 mg ml⁻¹, 0.65 mg ml⁻¹, and 22.64 mg ml⁻¹, respectively, and V_max values were 0.82 mol min⁻¹ mg⁻¹, 0.62 mol min⁻¹ mg⁻¹, and 104.17 mol min⁻¹ mg⁻¹ to cellulose, carboxymethyl cellulose, and xylan, respectively. In the saccharification tests, the total amount of total reducing sugars (TRS) released from 1 g of soybean hulls catalyzed by the enzymes present in the crude enzyme extract was 0.16 g g⁻¹ dry substrate.