BackgroundIntegrated statistical experimental designs were applied to optimize the medium constituents for the production of a dimethyl phthalate (DMP)-degrading strain Bacillus sp. QD14 in shake-flask cultures. A Plackett–Burman design (PBD) was applied to screen for significant factors, followed by the Steepest Ascent Method (SAM) to find the nearest region of maximum response. A Box–Behnken design (BBD) of the Response Surface Methodology (RSM) was conducted to optimize the final levels of the medium components.ResultsAfter the regression equation and response surface contour plots were analyzed, the concentrations of glucose, corn meal and NaCl were found to significantly influence the biomass of DMP-degrading bacteria. A combination of 22.88g/L of glucose, 11.74g/L of corn meal, and 10.34g/L of NaCl was optimum for maximum biomass production of Bacillus sp. QD14. A 57.11% enhancement of the biomass production was gained after optimization in shake-flask cultivation. The biomass production of Bacillus sp. QD14 reached 9.13±0.29×108CFU/mL, which was an excellent match for the predicted value, and the mean value of the match degree was as high as 99.30%.ConclusionIn this work, the key factors affected by the fermentation of DMP-degrading strain Bacillus sp. QD14 were optimized by PBD, SAM and BBD (RSM); the yield was increased by 57,11% in the conditions in our study. We propose that the conditions optimized in the study can be applied to the fermentation for commercialization production

Large quantities of phthalic acid esters (PAEs) are released and migrate into the environment continuously and become ubiquitous in soil, surface water, groundwater and other areas, eventually leading to serious environmental pollution. Therefore, the methods of PAEs mineralization have become a hot research topic. In this study, a highly efficient dimethyl phthalate (DMP)-degrading bacterium capable of utilizing DMP as the sole source of carbon and energy was isolated from frozen soil collected from a refuse disposal station. The DMP-degrading bacterium was identified as Pseudomonas sp. QDF12 according to the phylogeny of 16S rDNA sequence. The degradation process well fitted a first-order kinetic model, with a half-life of 9.8 h and the highest degradation rate of 20.19 mg/L•h at 15.0 °C. The fermentation conditions that enhanced the fermentation of biomass were optimized via Plackett-Burman design and response surface methodology. Finally, the carbon-nitrogen ratio, CaCO₃, temperature and shaking speed were identified as key factors. Verification experiments indicated that the maximal biomass was 1.85 × 10⁹ cfu/mL under the optimized conditions, which was 134.18% and 66.67% higher than those obtained under the Luria broth medium and the basic fermentation conditions, respectively. The time and temperature of fermentation were reduced to 12 h and 12.0 °C respectively. In conclusion, the strain QDF12 is more suitable for application in low-temperature areas owing to its fast, efficient fermentation and low-temperature resistance. Because of the shorter fermentation period and lower fermentation temperature, the large-scale commercial application of strain QDF12 will reduce the production costs and accelerate the fermentation speed.

The northern Songnen Plain in China is one of the most important areas for grain production in China, which has been increasingly affected by wind erosion in recent years. This study analyzed the dynamic spatiotemporal distribution of wind erosion in the northern Songnen Plain from 2010 to 2018 using the Revised Wind Erosion Equation model. The ecological service function of the study area was evaluated by constructing a spatial visualization map of windbreak and sand-fixation service flow. Wind erosion worsened from 2010 to 2018. The gravity center of different categories of wind erosion intensity moved to the northeast, indicating a risk of spreading from south to north. The amount of wind erosion in 2018 increased by 50.78% compared with 2010. The increase of wind force and temperature and the decrease of precipitation may have contributed to these trends. Long-term wind erosion led to soil coarsening, decreased soil organic matter, soil organic carbon, and total nitrogen contents, and increased soil CaCO₃ and pH, which may be one reason for slight soil salinization observed in some regions. Therefore, windbreak and sand-fixation management and eco-environmental protection are urgently required. This study is the first detailed assessment of wind erosion in the northern Songnen Plain on a regional scale and the first to propose measures for ecological restoration and desertification control.