This investigation was undertaken to determine the atrazine degradation by fungal enzyme extracts (FEEs) in a clay-loam soil microcosm contaminated at field application rate (5 μg g⁻¹) and to study the influence of different soil microcosm conditions, including the effect of soil sterilization, water holding capacity, soil pH and type of FEEs used in atrazine degradation through a 2⁴ factorial experimental design. The Trametes maxima–Paecilomyces carneus co-culture extract contained more laccase activity and hydrogen peroxide (H₂O₂) content (laccase = 18956.0 U mg protein⁻¹, H₂O₂ = 6.2 mg L⁻¹) than the T. maxima monoculture extract (laccase = 12866.7 U mg protein⁻¹, H₂O₂ = 4.0 mg L⁻¹). Both extracts were able to degrade atrazine at 100%; however, the T. maxima monoculture extract (0.32 h) achieved a lower half-degradation time than its co-culture with P. carneus (1.2 h). The FEE type (p = 0.03) and soil pH (p = 0.01) significantly affected atrazine degradation. The best degradation rate was achieved by the T. maxima monoculture extract in an acid soil (pH = 4.86). This study demonstrated that both the monoculture extracts of the native strain T. maxima and its co-culture with P. carneus can efficiently and quickly degrade atrazine in clay-loam soils.

In situ biosurfactant (rhamnolipid) production by Pseudomonas putida CB-100 was achieved during a bioaugmented and biostimulated treatment to remove hydrocarbons from aged contaminated soil from oil well drilling operations. Rhamnolipid production and contaminant removal were determined for several treatments of irradiated and non-irradiated soils: nutrient addition (nitrogen and phosphorus), P. putida addition, and addition of both (P. putida and nutrients). The results were compared against a control treatment that consisted of adding only sterilized water to the soils. In treatment with native microorganisms (non-irradiated soils) supplemented with P. putida, the removal of total petroleum hydrocarbons (TPH) was 40.6%, the rhamnolipid production was 1.54 mg/kg, and a surface tension of 64 mN/m was observed as well as a negative correlation (R = -0.54; p < 0.019) between TPH concentration (mg/kg) and surface tension (mN/m), When both bacteria and nutrients were involved, TPH levels were lowered to 33.7%, and biosurfactant production and surface tension were 2.03 mg/kg and 67.3 mN/m, respectively. In irradiated soil treated with P. putida, TPH removal was 24.5% with rhamnolipid generation of 1.79 mg/kg and 65.6 mN/m of surface tension, and a correlation between bacterial growth and biosurfactant production (R = -0.64; p < 0.009) was observed. When the nutrients and P. putida were added, TPH removal was 61.1%, 1.85 mg/kg of biosurfactants were produced, and the surface tension was 55.6 mN/m. In summary, in irradiated and non-irradiated soils, in situ rhamnolipid production by P. putida enhanced TPH decontamination of the soil.

The concentrations of hydrocarbons and organochlorine pesticides (OCPs), nutrients and tolerant microorganisms in an agricultural soil from a locality in Tepeaca, Puebla, Mexico, were determined to define its feasibility for bioremediation. The OCPs detected were heptachlor, aldrin, trans-chlordane, endosulfán I, endosulfán II, 1,1,1-bis-(4-chlorophenyl)-2,2-trichloroethane (4,4′-DDT), 1,1-bis-(4-chlorophenyl)-2,2-dichloroethene (4,4′-DDE) and endrin aldehyde, with values of 0.69–30.81 ng g⁻¹. The concentration of hydrocarbons in the soil of Middle Hydrocarbons Fraction (MHF), C₁₀ to C₂₈, was 4608–27,748 mg kg⁻¹ and 1117–19,610 mg kg⁻¹ for Heavy Hydrocarbons Fraction (HHF), C₂₈ to C₃₅, due to an oil spill from the rupture of a pipeline. The soil was deficient in nitrogen (0.03–0.07%) and phosphorus (0 ppm), and therefore it was advisable to fertilize to bio-stimulate the native microorganisms of soil. In the soil samples, hydrocarbonoclast fungi 3.72 × 10² to 44.6 × 10² CFU g⁻¹ d.s. and hydrocarbonoclast bacteria (0.17 × 10⁵ to 8.60 × 10⁵ CFU g⁻¹ d.s.) were detected, with a tolerance of 30,000 mg kg⁻¹ of diesel. Moreover, pesticideclast fungi (5.13 × 10² to 42.2 × 10² CFU g⁻¹ d.s.) and pesticideclast bacteria (0.15 × 10⁵ to 9.68 × 10⁵ CFU g⁻¹ d.s.) were determined with tolerance to 20 mg kg⁻¹ of OCPs. Fungi and bacteria tolerant to both pollutants were also quantified. Therefore, native microorganisms had potential to be stimulated to degrade hydrocarbons and pesticides or both pollutants. The concentration of pollutants and the microbial activity analyzed indicated that bioremediation of the soil contaminated with hydrocarbons and pesticides using bio-stimulation of native microorganisms was feasible.

This study evaluates the production of a biological active surface agent (BASA) through its surface tension (ST) and emulsifying activity (E₂₄) for endosulfan degradation (ED) and Escherichia coli growth inhibition (EcGI) in an agricultural saline soil. The fungus, identified as Penicillium crustosum was isolated from the Citrus sinensis peel (CsP), then the surface properties were evaluated in 9 culture media through a Taguchi L9 experimental design. The culture conditions included: stirring speed, pH, carbon (C) and nitrogen (N) sources; being glucose, NH₄N0₃, 120 rpm and pH of 5, the most significant parameters in the BASA production. The BASA identified as a lipopeptide type, showed a ST = 38 mN m⁻¹ and E₂₄=71%. Both properties were stable at 80 °C, while ST presented stability in the pH range of 2 – 12, and a saline concentration of 200 g L⁻¹; E₂₄ was also stable at a pH between 8–12. Further application of BASA and fungal inoculum to a contaminated agricultural saline soil presented an EcGI of 99.8% on the 8th day, and ED of 92.9 ± 4.7% in 30 days, respectively; being the first report that uses this fungus for pesticide and bacteria elimination from an agricultural saline soil.