Approaching chlorpyrifos bioelimination at bench scale bioreactor

Effect of microorganisms on degradation of fluopyram and tebuconazole in laboratory and field studies

Nowadays, chemical pesticides are the most widespread measure used to control crop pests and diseases. However, their negative side effects prompted the researchers to search for alternative options that were safer for the environment and people. Pesticide biodegradation by microorganisms seems to be the most reasonable alternative. The aim of the laboratory studies was to assess the influence of Bacillus subtilis and Trichoderma harzianum, used separately and combined together, on fluopyram and tebuconazole degradation. In field studies, the degradation of fluopyram and tebuconazole after the application of the biological preparation in apples was investigated. The results from the laboratory studies show that the greatest decomposition of fluopyram and tebuconazole was observed in tests with T. harzianum in a range of 74.3-81.5% and 44.5-49.2%, respectively. The effectiveness of fluopyram degradation by B. subtilis was 7.5%, while tebuconazole inhibited bacterial cell growth and no degradation was observed. The mixture of microorganisms affected the degradation of fluopyram in a range of 8.3-24.1% and tebuconazole in a range of 6.1-23.3%. The results from the field studies show that degradation increased from 3.1 to 30.8% for fluopyram and from 0.4 to 14.3% for tebuconazole when compared to control samples. The first-order kinetics models were used to simulate the residue dissipation in apples. For the determination of pesticide residues, the QuEChERS method for apple sample preparation was performed, followed by GC-MS/MS technique. Immediately after the treatments, the maximum residue level (MRL) values for tebuconazole were exceeded, and it was equal to 100.7% MRL for the Red Jonaprince variety and 132.3% MRL for the Gala variety. Thus, preharvest time is recommended to obtain apples in which the concentration of pesticides is below the MRL and which can be recognized as safe for humans.

Effects of biochar on biodegradation of sulfamethoxazole and chloramphenicol by Pseudomonas stutzeri and Shewanella putrefaciens: Microbial growth, fatty acids, and the expression quantity of genes

An incubation experiment was conducted to investigate whether different biochar could enhance the biodegradation of sulfamethoxazole (SMX) and chloramphenicol (CAP). During incubation in nutrient medium solution, the degradation efficiencies of SMX by P. stutzeri and S. putrefaciens obtained 61.79% and 68.67% respectively, while CAP was 85.75% and 85.70%. The biodegradation efficiencies of SMX and CAP increased for P. stutzeri cultured with biochar and increased for S. putrefaciens cultured with high-concentration biochar (500, 1,000, 2,000 mg L^-1). Additionally, TOC and TN contents were significantly decreased during the biodegradation process. Hence, the effects of biochar on microbial growth, fatty acids and expression genes, biodegradation products were studied. The content of bacteria, saturated fatty acids and expression genes showed a positive correlation with the content of TOC released from biochar, while the biodegradation products would not change when bacteria was cultured with biochar. These indicated that biochar improved the antibiotics biodegradation efficiencies via involvement in the bacterial growth, changing the components of fatty acids, increasing the expression quantity of genes. This research suggests that micro-biological degradation with biochar is a promising technology to treat specific antibiotics in the environment.

Organophosphorus compounds biodegradation by novel bacterial isolates and their potential application in bioremediation of contaminated water

Organophosphorus compounds (OPs), the major pesticides used worldwide, comprise an environmental hazard due to their harmful toxicity. Aimed to develop a bioreactor to remediate OPs contaminated wastewater, bacteria isolated from contaminated soils were identified and their ability to degrade OPs assessed, resulting in two main isolates, Sphingomonas sp. and Brevundimonas sp. Their OP degrading activities were characterized in terms of temperature, pH and substrates acceptance, resulting in high degradation rates at 60 °C, pH 10 and towards bulky OPs such as coroxon, coumaphos, and chlorpyrifos. Sphingomonas sp. cells were immobilized and 75.4% degradation of 0.15 mM chlorpyrifos was achieved after 21 days by immobilized cells in batch system, while this OP was completely degraded within 17 h when the biocatalyst is settled in a packed bed bioreactor, with a reusability of 8 cycles. These results suggest the potential application of this system in the bioremediation of contaminated wastewater.

Simultaneous biotreatment of Polycyclic Aromatic Hydrocarbons and dyes in a one-step bioreaction by an acclimated Pseudomonas strain

A Pseudomonas stutzeri strain acclimated to the presence of neoteric contaminants has been proposed for simultaneously remediating an effluent polluted with Polycyclic Aromatic Hydrocarbons and a diazo dye. The pollutants chemical nature imposed a strict control of both the medium composition and the operating conditions. pH, temperature and agitation rates of 7.0, 37.5 and 146 rpm, respectively, led to optimum levels of contaminant removal (higher than 60%) after RSM optimization. The validity of these conditions was checked at flask and bioreactor scale and the kinetics of the biotreatment was elucidated. The simulation of this one-step process applied at larger scale for the remediation of a 200,000 m(3)/year-effluent from a leather factory was compared with a conventional two-steps option. Great reductions in treatment times and in investment and manufacturing costs were concluded, proving the promising potential of the proposed process.