Biochemical tests to determine the biodegradability potential of bacterial strains in PAH polluted sites

Cyanobacterial biocrust alters soil physical properties reducing soil erosion and aerosol production

Aerosol emission by wind erosion in the arid and semi-arid areas of the world, is of environmental and health significance. Different methods have been used to mitigate aerosol emission among which the biological methods may be the most efficient ones. Although previously investigated, more research is essential to determine how the use of exopolysaccharide (biocrust)-producing cyanobacteria may affect soil physical properties. The objective was to investigate the effects of the cyanobacteria, Microcoleus vaginatus ATHK43 (identified and registered by the NCBI accession number MW433686), on soil physical properties of a sandy soil 15, 30, 60, and 90 d after inoculation. The effects of cyanobacterial biocrust on soil properties including shear strength, soil resistance, aggregate stability (mean weight diameter (MWD) and geometric mean diameter (GMD)), and wind erosion were determined in trays using a wind tunnel. Cyanobacterial inoculation significantly increased MWD (0-1 cm depth, from 0.12 mm to 0.47 mm) and GMD (from 0.3 to 0.5 mm) after a period of 90 d. Biocrust production significantly decreased soil erosion from 55.7 kgm- 2 to 0.3 kgm- 2 (wind rate of 50 kmh- 1), and from 116.42 kgm- 2 to 0.6 kgm- 2 (wind rate of 90 kmh- 1) after 90 d. In conclusion, cyanobacterial biocrust can significantly improve soil physical properties in different parts of the world including the deserts, and reduce aerosol emission by mitigating the destructive effects of wind erosion on soil physical properties.

The mechanism of anthracene degradation by tryptophan -2,3-dioxygenase (T23D) in Comamonas testosteroni

It is well known that anthracene is a persistent organic pollutant. Among the four natural polycyclic aromatic hydrocarbons (PAHs) degrading strains, Comamonas testosterone (CT1) was selected as the strain with the highest degradation efficiency. In the present study, prokaryotic transcriptome analysis of CT1 revealed an increase in a gene that encodes tryptophane-2,3-dioxygenase (T23D) in the anthracene and erythromycin groups compared to CK. Compared to the wild-type CT1 strain, anthracene degradation by the CtT23D knockout mutant (CT-M1) was significantly reduced. Compared to Escherichia coli (DH5α), CtT23D transformed DH5α (EC-M1) had a higher degradation efficiency for anthracene. The recombinant protein rT23D oxidized tryptophan at pH 7.0 and 37 °C with an enzyme activity of 2.42 ± 0.06 μmol min-1·mg-1 protein. In addition, gas chromatography-mass (GC-MS) analysis of anthracene degradation by EC-M1 and the purified rT23D revealed that 2-methyl-1-benzofuran-3-carbaldehyde is an anthracene metabolite, suggesting that it is a new pathway.

Chromium (VI) bioremoval from contaminated wastewater using Pseudomonas aeruginosa ATHA23 producing biofilm supported on clinoptilolite

More has yet to be investigated on the increased efficiency of microbes for the removal of heavy metals from industrial wastewaters. The objective was to determine the Cr (VI) bioabsorption and bioreduction ability of biofilm-producing bacteria supported on clinoptilolite from contaminated aqueous solutions. Chromium (VI)-tolerant bacteria, namely Pseudomonas aeruginosa ATHA23, were identified by biochemical methods and 16S rDNA sequencing and were deposited in NCBI (accession number: KF680991). Preparation of clinoptilolite, bacterial growth and isolation, biofilm production including extracellular polysaccharides (EPS) and Cr (VI) removal efficiency, affected by the experimental treatments, were investigated. The use of FTIR characterized clinoptilolite properties with and without biofilm in the presence and absence of Cr (IV). Higher Cr (VI) levels in the bacterial growth medium, increased EPS production with the highest value (0.171 mg L^-1), produced 18 h after treating the bacteria with Cr (VI) (100 mg L^-1). However, in the absence of Cr (VI), EPS significantly decreased to 0.117 mg L^-1. Plackett-Burman and Taguchi statistical analyses were used to optimize the experimental treatments affecting the removal efficiency of Cr (VI). Among the anions (nitrate, sulfate, and chloride), sulfate decreased Cr removal efficiency. The absorption data were best fitted to the pseudo-second order, and the data of Cr adsorption by clinoptilolite-biofilm were also better fitted to Freundlich isotherm model. The Cr (VI) bioremediation potential of P. aeruginosa ATHA23 by the production of biofilm supported on clinoptilolite has been shown for the first time, which is of significance for the environment and the industry.

Biostimulation and Bioaugmentation of Soils Contaminated with Decachlorobiphenyl (PCB-209) Using Native Bacterial Strains Individually and in Consortia

Historically, microorganisms have proven to be efficient alternatives for the removal of PCBs, since these contaminants continue to be a major problem for human health and the environment. In this work, the removal of decachlorobiphenyl (PCB-209) was evaluated using native bacterial strains individually and in consortia through biostimulation and bioaugmentation processes. Bacillus sp. DCB13, Staphylococcus sp. DCB28, and Acinetobacter sp. DCB104 were biostimulated in a minimal medium that initially contained biphenyl and later PCB-209 for adaptation as a carbon source. The removal potential of PCB-209 by bacterial strains was evaluated in a bioaugmentation process under aerobic conditions. Using a completely randomized design, ten different treatments were evaluated. Finally, the bacterial growth (CFU/g of soil) and the chemical characteristics of the bioaugmented soil were determined, as was the content of PCB-209 removed by gas chromatography–mass spectrometry. Strains DCB13, DCB28, and DCB104 showed cell growth (>3.4 × 105 CFU/mL) during 120 h of biostimulation, with a marked difference between treatments with biphenyl compared with those where PCB-209 was added. Strains DCB13 and DCB104 (3.4 × 105 CFU/mL and 2.0 × 106 CFU/mL, respectively) grew better with PCB-209, while DCB28 grew better with biphenyl (4.5 × 106 CFU/mL). In bioaugmented soils contaminated with PCB-209, the strains showed maximum growth when inoculated in a consortium (>2.0 × 104 CFU/g). The results showe that the range of the bacterial elimination of PCB-209 in the treatments was from 9.58 to 17.33 mg/kg. The highest elimination potential of PCB-209 was obtained when the bacterial strains were inoculated in a consortium. These findings open a wide perspective for the use of native bacteria for the cleaning and restoration of soils contaminated by toxic chemicals.

Improved degradation of petroleum hydrocarbons by co-culture of fungi and biosurfactant-producing bacteria

Microbial remediation has proven to be an effective technique for the cleanup of crude-oil contaminated sites. However, limited information exists on the dynamics involved in defined co-cultures of biosurfactant-producing bacteria and fungi in bioremediation processes. In this study, a fungal strain (Scedosporium sp. ZYY) capable of degrading petroleum hydrocarbons was isolated and co-cultured with biosurfactant-producing bacteria (Acinetobacter sp. Y2) to investigate their combined effect on crude-oil degradation. Results showed that the surface tension of the co-culture decreased from 63.12 to 47.58 mN m^-1, indicating the secretion of biosurfactants in the culture. Meanwhile, the degradation rate of total petroleum hydrocarbon increased from 23.36% to 58.61% at the end of the 7-d incubation period. In addition, gas chromatography - mass spectrometry analysis showed a significant (P < 0.05) degradation from 3789.27 mg/L to 940.33 mg/L for n-alkanes and 1667.33 μg/L to 661.5 μg/L for polycyclic aromatic hydrocarbons. Moreover, RT-qPCR results revealed the high expression of alkB and CYP52 genes by Acinetobacter sp. Y2 and Scedosporium sp. ZYY respectively in the co-culture, which corelated positively (P < 0.01) with n-alkane removal. Finally, microbial growth assay which corresponded with Fluorescein diacetate hydrolysis activity, highlighted the synergistic behavior of both strains in tackling the crude oil. Findings in this study suggest that the combination of fungal strain and biosurfactant-producing bacteria effectively enhances the degradation of petroleum hydrocarbons, which could shed new light on the improvement of bioremediation strategies.