Ultrasonic-assisted biodegradation of endocrine disrupting compounds by Pseudomonas putida the importance of rhamnolipid for intermediate product degradation

Nutrient and organic pollutants removal in synthetic wastewater by Pseudomonas aeruginosa and Chryseobacterium sp./biofilter systems

Nutrient and organic pollution raise serious problems for aquatic ecosystems through the accumulation of organic carbon, the reduction of light penetration, and the loss of submerged aquatic vegetation. The over-enrichment of water with nitrogen and phosphorus leads to an imbalance in nutrient ratios, creating favorable conditions for toxic algal blooms, formation of oxygen-depleted water, etc. Thus, developing new technological solutions to reduce their amount is imperative. The present study investigates the capacity of Pseudomonas aeruginosa and Chryseobacterium sp. bacterial strains to form biofilm on solid support (biofilter), both individually and in tandem, using various analytical techniques. Also, the biofilm/biofilter systems' efficiency in removing nutrients such as nitrate, nitrite, ammonium, and phosphate ions from municipal wastewaters is assessed. The results showed a reduction of nutrient pollution of up to 91%, 98%, 55%, and 71% for nitrite, nitrate, ammonium, and phosphate ions. A reduction of about 78% of COD was also observed. The results were obtained in the absence of an additional aeration process, thus having a great potential for reducing total costs of wastewater treatment and developing ecological systems for wastewater management.

Nutrients Removal from Aquaculture Wastewater by Biofilter/Antibiotic-Resistant Bacteria Systems

The presence of nutrients in aquaculture water bodies causes serious problems for aquatic ecosystems, requiring the development of technical solutions to reduce their amounts. This work identifies some bacterial strains that are able to reduce nutrient quantities and studies the effect of antibiotics on bacterial growth, on the ability to form biofilms on different solid supports, and on the ability to reduce nutrients in aquaculture wastewater. Bacterial biofilm adhesion on different substrates depends on the surface properties of the substrate, on the bacterial types that form the biofilm, but also on biofilm–substrate interactions. The obtained results revealed the high capacity of biofilm-forming bacterial strains of Pseudomonas aeruginosa and Chromobacterium violaceum to eliminate up to 87% of nitrate and nitrite ions and up to 62% of phosphate ions in the presence of concentrations of 0.1–0.4 µg/mL of oxytetracycline antibiotic from aquaculture wastewater.

Responses of steroid estrogen biodegradation to cyanobacterial organic matter biodegradability in the water column of a eutrophic lake

The co-occurrence of cyanobacterial harmful algal blooms and contaminants is an increasing environmental concern in freshwater worldwide. Our field investigations coupled with laboratory incubations demonstrated that the microbial degradation potential of 17β-estradiol (E2) with estrone as the intermediate was primarily driven by increased dissolved organic matter (DOM) in the water column of a cyanobacterial bloom. To explain the intrinsic contribution of cyanobacterial-derived DOM (C-DOM) to estrogen biodegradation, a combination of methods including bioassay, ultrahigh-resolution mass spectrometry, and microbial ecology were applied. The results showed that preferential assimilation of highly biodegradable structures, including protein-, carbohydrate-, and unsaturated hydrocarbon-like molecules sustained bacterial growth, selected for more diverse microbes, and resulted in greater estrogen biodegradation compared to less biodegradable molecules (lignin- and tannin-like molecules). The biodegradability of C-DOM decreased from 78% to 1%, whereas the E2 biodegradation rate decreased dramatically at first, then increased with the accumulation of recalcitrant, bio-produced lipid-like molecules in C-DOM. This change was linked to alternative substrate-induced selection of the bacterial community under highly refractory conditions, as suggested by the greater biomass-normalized E2 biodegradation rate after a 24-h lag phase. In addition to the increased frequency of potential degraders, such as Sphingobacterium, the network analysis revealed that C-DOM molecules distributed in high H/C (protein- and lipid-like molecules) were the main drivers structuring the bacterial community, inducing strong deterministic selection of the community assemblage and upregulating the metabolic capacity for contaminants. These findings provide strong evidence that estrogen biodegradation in eutrophic water may be facilitated by cyanobacterial blooms and provide a theoretical basis for ecological remediation of estrogen pollution.

Prediction of Biodegradability for Polycyclic Aromatic Hydrocarbons Using Various In Silico Modeling Methods

Polycyclic aromatic hydrocarbons (PAHs) have attracted great concern as global environmental pollutants. In this work, the quantitative structure-biodegradability relationship (QSBR) study has been done to predict the biodegradability of PAHs and develop the correlation between the biodegradability and the molecular structures. The structural chemistry and quantum chemistry descriptors were used to represent molecular structures. Three in silico modeling methods, i.e., multiple linear regression (MLR), radial basis function neural network, and back-propagation artificial neural network (BPANN), are utilized to construct the linear and nonlinear prediction models and provide some insights into the structural characteristics affecting the biodegradability of PAHs. The stability of these QSBR models was tested by leave-one-out cross-validation, and the cross-validated correlation coefficients (q²) were 0.6109, 0.6887, and 0.6586, respectively. The correlation coefficients (R²) of the three models for the training set were 0.7811, 0.8883, and 0.9667, respectively. The comparison of the three models showed that the BPANN model produced a statistically more significant model than the other two models. On the basis of molecular structure, the dominant molecular structure descriptor affecting biodegradability of PAHs were analyzed and discussed.