Biodegradation of diesel oil and production of fatty acid esters by a newly isolated Pseudomonas citronellolis KHA

Assessing Diesel Tolerance of Chromobacterium violaceum: Insights from Growth Kinetics, Substrate Utilization, and Implications for Microbial Adaptation

This study aimed to determine the tolerance of Chromobacterium violaceum ATCC 12472 to diesel. The growth of the strain was evaluated through exposure to various diesel concentrations (1, 2.5, 5, 7.5, and 10% v/v), with continuous monitoring of growth via optical density measurements until the death phase was reached. Employing a logistic model, we analyzed the growth kinetics of C. violaceum and compared them with five other models to comprehend substrate utilization dynamics. Our results indicate that optimal bacterial growth occurred at 2.5% (v/v) or 18,125 mg/L diesel, while both higher and lower concentrations manifested inhibitory and increasingly stressful effects. The Aiba model emerged as the most fitting representation of substrate utilization by C. violaceum. In addition, our findings underscore the remarkable diesel tolerance of C. violaceum ATCC 12472, despite the inherently stressful nature of the medium. This study contributes to the understanding of microbial responses to environmental stressors and highlights the pivotal role of the substrate concentration in influencing microbial growth. These insights have implications for bioremediation strategies and enhance our understanding of bacterial ecological resilience in the presence of hydrocarbon pollutants.

Biodegradation of clopidogrel bisulfate by Pseudomonas aeruginosa and Pseudomonas putida strains isolated from Algerian wastewater

The clopidogrel bisulfate was degraded under aerobic conditions by two bacterial strains isolated from industrial effluents in El-Harrach, Algeria. The sequencing of their 16S rRNA revealed that these two strains are Pseudomonas aeruginosa and Pseudomonas putida. The experiments showed that this consortium could remove clopidogrel bisulfate at high concentrations (5-1500 mg·L^-1) within 96 h incubation period. The HPLC analysis recorded 75.23% degradation of clopidogrel bisulfate at an initial concentration of 100 mg·L^-1 after five days of incubation at pH 7.0 and a temperature of 30 °C. Also, a maximum degradation of 99.08% was carried out at a more basic pH (8.5). While only 41% was degraded at a temperature of 20 °C. Moreover, the presence of supplemental sources of carbon and nitrogen in the mixed culture media effectively improved the biodegradation of clopidogrel bisulfate by the stains. Finally, the morphology of the strains and the properties of the cell's surface were studied using a scanning electron microscope (SEM). This study reports, for the first time, the viability of the aerobic biodegradation of clopidogrel bisulfate in water in a wide range of concentrations.

Uptake and detoxification of diesel oil by a tropical soil Actinomycete Gordonia amicalis HS-11: Cellular responses and degradation perspectives

A tropical soil Actinomycete, Gordonia amicalis HS-11, has been previously demonstrated to degrade unsaturated and saturated hydrocarbons (squalene and n-hexadecane, respectively) in an effective manner. In present study, G. amicalis HS-11 degraded 92.85 ± 3.42% of the provided diesel oil [1% (v/v)] after 16 days of aerobic incubation. The effect of different culture conditions such as carbon source, nitrogen source, pH, temperature, and aeration on degradation was studied. During degradation, this Actinomycete synthesized surface active compounds (SACs) in an extracellular manner that brought about a reduction in surface tension from 69 ± 2.1 to 30 ± 1.1 mN m^-1 after 16 days. The morphology of cells grown on diesel was monitored by using a Field Emission Scanning Electron Microscope. Diesel-grown cells were longer and clumped with smooth surfaces, possibly due to the secretion of SACs. The interaction between the cells and diesel oil was studied by Confocal Laser Scanning Microscope. Some cells were adherent on small diesel droplets and others were present in the non-attached form thus confirming the emulsification ability of this organism. The fatty acid profiles of the organism grown on diesel oil for 48 h were different from those on Luria Bertani Broth. The genotoxicity and cytotoxicity of diesel oil before and after degradation were determined. Cytogenetic parameters such as mitotic index (MI); mitosis distribution and chromosomal aberration (type and frequency) were assessed. Oxidative stress was evaluated by measuring levels of catalase, superoxide dismutase and concentration of malondialdehyde. On the basis of these studies it was deduced that the degradation metabolites were relatively non-toxic.

Biodegradation of anionic surfactants by Alcaligenes faecalis, Enterobacter cloacae and Serratia marcescens strains isolated from industrial wastewater

Pseudo-persistent organic pollutants, such as anionic surfactants (AS), are nowadays among the more complex problems that threaten the aquatic environments and other environmental compartments. The present work describes the identification and efficiency of a consortium, isolated from Algerian industrial wastewater, to remove three anionic surfactants (i.e., sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS) and sodium lauryl ether sulfate (SLES)). The genetic analysis of 16S rRNA indicated that these strains are Alcaligenes faecalis, Enterobacter cloacae and Serratia marcescens. Under aerobic conditions, pH 7.0 and optimum temperature of 30 °C, the mixed consortium allowed to degrade 85.1% of initial SDBS amount after 144 h of incubation with half-life of 20.8 h. While E. cloacae and S. marcescens pure strains eliminated 46% and 41% less SDBS respectively. Evenly, SDS was degraded at only 23.71% by A. faecalis strain. However, the degradation capacity of SDS by the consortium was very high (94.2%) with a half-life of 9.8 h. The SLES anionic surfactant showed a lower biodegradation by the consortium (47.53%) due to the presence of ether oxide units in the chemical structure of SLES which induced toxicity to the medium. The investigation of the biodegradation of this type of organic pollutants by microorganisms has recently become a key issue for the environmental protection area.

Molecular and Microbiological Insights on the Enrichment Procedures for the Isolation of Petroleum Degrading Bacteria and Fungi

Autochthonous bioaugmentation, by exploiting the indigenous microorganisms of the contaminated environment to be treated, can represent a successful bioremediation strategy. In this perspective, we have assessed by molecular methods the evolution of bacterial and fungal communities during the selective enrichment on different pollutants of a soil strongly polluted by mixtures of aliphatic and polycyclic hydrocarbons. Three consecutive enrichments were carried out on soil samples from different soil depths (0-1, 1-2, 2-3 m), and analyzed at each step by means of high-throughput sequencing of bacterial and fungal amplicons biomarkers. At the end of the enrichments, bacterial and fungal contaminants degrading strains were isolated and identified in order to (i) compare the composition of enriched communities by culture-dependent and culture-independent molecular methods and to (ii) obtain a collection of hydrocarbon degrading microorganisms potentially exploitable for soil bioremediation. Molecular results highlighted that for both bacteria and fungi the pollutant had a partial shaping effect on the enriched communities, with paraffin creating distinct enriched bacterial community from oil, and polycyclic aromatic hydrocarbons generally overlapping; interestingly neither the soil depth or the enrichment step had significant effects on the composition of the final enriched communities. Molecular analyses well-agreed with culture-dependent analyses in terms of most abundant microbial genera. A total of 95 bacterial and 94 fungal strains were isolated after selective enrichment procedure on different pollutants. On the whole, isolated bacteria where manly ascribed to Pseudomonas genus followed by Sphingobacterium, Bacillus, Stenothrophomonas, Achromobacter, and Serratia. As for fungi, Fusarium was the most abundant genus followed by Trichoderma and Aspergillus. The species comprising more isolates, such as Pseudomonas putida, Achromobacter xylosoxidans and Ochromobactrum anthropi for bacteria, Fusarium oxysporum and Fusarium solani for fungi, were also the dominant OTUs assessed in Illumina.

High molecular weight bioemulsifiers, main properties and potential environmental and biomedical applications

High molecular weight bioemulsifiers are amphipathic polysaccharides, proteins, lipopolysaccharides, lipoproteins, or complex mixtures of these biopolymers, produced by a wide variety of microorganisms. They are characterized by highly structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface respectively and/or emulsify hydrophobic compounds. Emulsan, fatty acids, phospholipids, neutral lipids, exopolysaccharides, vesicles and fimbriae are among the most popular high molecular weight bioemulsifiers. They have great physic-chemical properties like tolerance to extreme conditions of pH, temperature and salinity, low toxicity and biodegradability. Owing their emulsion forming and breaking capacities, solubilization, mobilization and dispersion activities and their viscosity reduction activity; they possess great environmental application as enhancer of hydrocarbon biodegradation and for microbial enhanced oil recovery. Besides, they are applied in biomedical fields for their antimicrobial and anti-adhesive activities and involvement in immune responses.