Exploring the potential of halotolerant bacteria for biodegradation of polycyclic aromatic hydrocarbon

Degradation of anthracene and phenanthrene by strain Streptomyces sp. M-1 and its application in the treatment of PAHs-contaminated water

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants with mutagenicity, carcinogenicity and teratogenicity, widely distributed in the environment. Effective biodegradation of PAHs is highly required, especially in wastewater. An efficient PAHs degrading strain Streptomyces sp. M-1 was isolated from polluted kerosene. The degradation capacity of anthracene and phenanthrene was evaluated under various PAHs concentrations, pH, and temperatures by M-1. To find the degradation pathways, the key intermediates were detected by mass spectrometry and the enzyme-encoding genes were analyzed by many bioinformatics tools. Furthermore, the potential of the strain for bioremediation in PAH-contaminated water was evaluated. The results showed that the maximal degradation rate of anthracene and phenanthrene reached 93.14% (100 mg L-1, 7 days) and 49.25% (50 mg L-1, 7 days), respectively. Their average degradation rate increased within the concentration of 50-800 mg L-1 and reached 2.72 mg d-1 for anthracene and 1.28 mg d-1 for phenanthrene at 800 mg L-1. M-1 exhibited high and stable anthracene degradation rate under tested pH and temperatures, and high phenanthrene degradation under tested pH and higher temperatures. Based on the analysis of both intermediates and enzyme-encoding genes, it is proposed that anthracene undergoes degradation via the phthalic acid pathway, while phenanthrene follows the salicylic acid pathway. Finally, 98.98% degradation of anthracene and 72.77% degradation of phenanthrene in water was realized over 14 days. We thus propose that Streptomyces sp. M-1 is an effective degrader for bioremediation of PAHs pollution.

Bacterial Degradation of Petroleum Hydrocarbons in Saudi Arabia

The Kingdom of Saudi Arabia (KSA) is the leading oil-exploring and -exploiting country in the world. As a result, contamination of the environment by petroleum products (mainly hydrocarbons) is common, necessitating strategies for their removal from the environment. Much work has been conducted on bacterial degradation of hydrocarbons in the KSA. This review comprehensively analyzed 43 research investigation articles on bacterial hydrocarbon degradation, mainly polyaromatic hydrocarbons (PAHs) within the KSA. More than 30 different bacterial genera were identified that were capable of degrading simple and complex PAHs, including benzo[a]pyrene and coronene. Different strategies for selecting and isolating these bacterial strains and their advantages and disadvantages were highlighted. The review also discussed the origins of sample inocula and the contributions of various research groups to this field. PAH metabolites produced by these bacteria were presented, and biochemical pathways of PAH degradation were proposed. More importantly, research gaps that could enrich our understanding of petroleum product biodegradation mechanisms were highlighted. Overall, the information presented in this paper will serve as a baseline for further research on optimizing bioremediation strategies in all petroleum-contaminated environments.

Green titanium dioxide (TiO2) nanoparticles assisted biodegradation of anthracene employing Serratia quinivorans HP5

The anthracene biodegradation potential of Serratia quinivorans HP5 was studied under a controlled laboratory environment. The green TiO2 nanoparticles (NPs) synthesized from Paenibacillus sp. HD1PAH was used to accelerate the biodegradation process. The synergistic application of TiO2 NPs and S. quinivorans HP5 resulted in a reduction of anthracene concentration by 1.2 folds in liquid-medium and 1.5 folds in contaminated soil. Gas-chromatography and mass-spectrometric investigation showed the production of four anthracene derivatives, namely 1,2-anthracene dihydrodiol, 6,7-benzocoumarin, anthrone, and 9,10-anthraquinoneat the termination of experimental periods. Furthermore, bacterial biomass increased by 23.3 folds in the presence of TiO2 NPs, and overall soil enzyme activities were enhanced by 4.2 folds in the treated samples. In addition, there was a negative correlation observed between the biomass of S. quinivorans HP5 and the concentrations of anthracene, suggesting the involvement of bacterium in anthracene biodegradation processes. The degradation pathway of anthracene revealed its transformation into the less toxic compound 9,10-anthraquinone. Overall, this study elucidates a novel biodegradation pathway for anthracene and highlights the potential of nano-assisted bacterial remediation as a promising approach for environmental cleanup.

Functional activity of endophytic bacteria G9H01 with high salt tolerance and anti-Magnaporthe oryzae that isolated from saline-alkali-tolerant rice

It holds significant practical importance to screen and investigate endophytic bacteria with salt-tolerant activity in rice for the development of relevant microbial agents. A total of 179 strains of endophytic bacteria were isolated from 24 samples of salt-tolerant rice seeds, with almost 95 % of these bacteria exhibiting tolerance to a salt content of 2 % (0.34 mol/L). Following the screening process, a bacterium named G9H01 was identified, which demonstrated a salt tolerance of up to 15 % (2.57 mol/L) and resistance to Magnaporthe oryzae, the causal agent of rice blast disease. Phylogenetic analysis confirmed G9H01 as a strain of Bacillus paralicheniformis. The complete genome of G9H01 was sequenced and assembled, revealing a considerable number of genes encoding proteins associated with salt tolerance. Further analysis indicated that G9H01 may alleviate salt stress in a high-salt environment through various mechanisms. These mechanisms include the utilization of proteins such as K+ transporters, antiporters, and Na+/H+ antiporters, which are involved in K+ absorption and Na+ excretion. G9H01 also demonstrated the ability to uptake and accumulate betaine, as well as secrete extracellular polysaccharides. Collectively, these findings suggest that Bacillus paralicheniformis G9H01 has potential as a biocontrol agent, capable of promoting rice growth under saline-alkali-tolerant conditions.

Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Degradation of polycyclic aromatic hydrocarbons in aquatic environments by a symbiotic system consisting of algae and bacteria: green and sustainable technology

Polycyclic aromatic hydrocarbons (PAHs) are genotoxic, carcinogenic, and persistent in the environment and are therefore of great concern in the environmental protection field. Due to the inherent recalcitrance, persistence and nonreactivity of PAHs, they are difficult to remediate via traditional water treatment methods. In recent years, microbial remediation has been widely used as an economical and environmentally friendly degradation technology for the treatment of PAH-contaminated water. Various bacterial and microalgal strains are capable of potentially degrading or transforming PAHs through intrinsic metabolic pathways. However, their biodegradation potential is limited by the cytotoxic effects of petroleum hydrocarbons, unfavourable environmental conditions, and biometabolic limitations. To address this limitation, microbial communities, biochemical pathways, enzyme systems, gene organization, and genetic regulation related to PAH degradation have been intensively investigated. The advantages of algal-bacterial cocultivation have been explored, and the limitations of PAHs degradation by monocultures of algae or bacteria have been overcome by algal-bacterial interactions. Therefore, a new model consisting of a "microalgal-bacterial consortium" is becoming a new management strategy for the effective degradation and removal of PAHs. This review first describes PAH pollution control technologies (physical remediation, chemical remediation, bioremediation, etc.) and proposes an algal-bacterial symbiotic system for the degradation of PAHs by analysing the advantages, disadvantages, and PAH degradation performance in this system to fill existing research gaps. Additionally, an algal-bacterial system is systematically developed, and the effects of environmental conditions are explored to optimize the degradation process and improve its technical feasibility. The aim of this paper is to provide readers with an effective green and sustainable remediation technology for removing PAHs from aquatic environments.

Aromatic compounds depurative and plant growth promotion rhizobacteria abilities of Allenrolfea vaginata (Amaranthaceae) rhizosphere microbial communities from a solar saltern hypersaline soil

Introduction

This work investigates whether rhizosphere microorganisms that colonize halophyte plants thriving in saline habitats can tolerate salinity and provide beneficial effects to their hosts, protecting them from environmental stresses, such as aromatic compound (AC) pollution.

Methods

To address this question, we conducted a series of experiments. First, we evaluated the effects of phenol, tyrosine, 4-hydroxybenzoic acid, and 2,4-dichlorophenoxyacetic (2,4-D) acids on the soil rhizosphere microbial community associated with the halophyte Allenrolfea vaginata. We then determined the ability of bacterial isolates from these microbial communities to utilize these ACs as carbon sources. Finally, we assessed their ability to promote plant growth under saline conditions.

Results

Our study revealed that each AC had a different impact on the structure and alpha and beta diversity of the halophyte bacterial (but not archaeal) communities. Notably, 2,4-D and phenol, to a lesser degree, had the most substantial decreasing effects. The removal of ACs by the rhizosphere community varied from 15% (2,4-D) to 100% (the other three ACs), depending on the concentration. Halomonas isolates were the most abundant and diverse strains capable of degrading the ACs, with strains of Marinobacter, Alkalihalobacillus, Thalassobacillus, Oceanobacillus, and the archaea Haladaptatus also exhibiting catabolic properties. Moreover, our study found that halophile strains Halomonas sp. LV-8T and Marinobacter sp. LV-48T enhanced the growth and protection of Arabidopsis thaliana plants by 30% to 55% under salt-stress conditions.

Discussion

These results suggest that moderate halophile microbial communities may protect halophytes from salinity and potential adverse effects of aromatic compounds through depurative processes.

Anthracene removal potential of green synthesized titanium dioxide nanoparticles (TiO2-NPs) and Alcaligenes faecalis HP8 from contaminated soil

Anthracene biodegradation potential has been studied in liquid culture and soil microcosm environment by employing green synthesized TiO₂ nanoparticles (NPs) and Alcaligenes faecalis HP8. The bacterium was isolated from crude oil contaminated soil, while TiO₂ nanoparticles were synthesized using Paenibacillus sp. HD1PAH and Cyperus brevifolius which have PAHs remediation abilities. The dual application of TiO₂ nanoparticles and Alcaligenes faecalis HP8 decreases anthracene concentration up to 21.3% in liquid at the end of 7 days and 37.9% in the soil treatments after completion of 30 days. Besides, the GC-MS analysis revealed production of five metabolites including 1,2-anthracenedihydrodiol; 6,7-benzocoumarin; 3-hydroxy-2-naphthoic acid; salicylic acid and 9,10-anthraquinone at different time interval of the treatments. Anthracene degradation pathway confirms the breakdown of three ring anthracene to one ring salicylic acid. Additionally, soil dehydrogenase, urease, alkaline phosphatase, catalase and amylase activities increased up to 4.09 folds, 8.6 folds, 4.4 folds, 3.6 folds and 2.1 folds respectively after the combined treatments of TiO₂ nanoparticles and Alcaligenes faecalis HP8. The bacterial biomass and residual anthracene concentration were found to be negatively correlated. Finally, the study brings into light a novel anthracene biodegradation pathway and provides a new dimension in nano assisted bacterial remediation.

Microbial degradation and transformation of benzo[a]pyrene by using a white-rot fungus Pleurotus eryngii F032

Polycyclic aromatic hydrocarbons (PAHs) are environmentally recalcitrant contaminants formed from naturally or incomplete combustion of organic materials and some of them are difficult to degrade due to their hydrophobicity and persistency. Benzo [a]pyrene (BaP), is one of PAHs that having five fused benzene and reported as mutagenic, carcinogenic and teratogenic compounds. Biodegradation is one of promising techniques due to its relatively low economic cost and microorganism is a natural capacity to consume hydrocarbons. In this investigation, Pleurotus eryngii F032 was grown in 20 mL of modified mineral salt broth (MSB) supplemented with BaP under static and agitated culture. Within 20 days, static culture removed 59% of BaP, whereas agitated culture removed the highest amount (73%). To expedite BaP elimination, the mechanism and behavior of BaP biosorption and biotransformation by Pleurotus eryngii F032 were additionally examined by gas chromatography-mass spectrometer (GC-MS). The optimal conditions for P. eryngii F032 to eliminate BaP were 25 °C, a C/N ratio of 8, pH 3 and 0.2% inoculum concentration. At an initial BaP content of 10 mg/L, more than 50% was effectively eliminated within 20 days under these conditions. Salinity, glucose, and rhamnolipids were the most important factors impacting BaP biodegradation. GC-MS found degradation products such as BaP-3,6-quinone, indicating plausible metabolic routes. Finally, it may be assumed that the primary mechanism by which white-rot fungi eliminate BaP is by the utilization of biotransformation enzymes such as laccase to mineralize the PAHs. Hence, Pleurotus eryngii F032 could be an ideal candidate to treat PAHs contaminated soils.

Halomonas jincaotanensis sp. nov., isolated from the Pamir Plateau degrading polycyclic aromatic hydrocarbon

A Gram-strain-negative, rod-shaped, aerobic bacterium, designated strain TRM 85114^T, was isolated from the Jincaotan wetland in the Pamir Plateau of China. This strain grew optimally at 30 °C and pH 6.0 in the presence of 3% (w/v) NaCl. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain TRM 85114^T was affiliated with the genus Halomonas, and shared high sequence similarity with Halomonas korlensis XK1^T (97.3%) and Halomonas tibetensis pyc13^T (96.4%). Strain TRM 85114^T contained C_16:0 and C_19:0 cyclo ω8c as primary cellular fatty acids, Q-9 as predominate respiratory quinone, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phospholipids of unknown structure containing glucosamine, unidentified aminophospholipids, unidentified lipids and three unidentified phospholipids as the major polar lipids. The complete genome of TRM 85114^T comprised 3,902 putative genes with a total of 4,126,476 bp and a G + C content of 61.6%. The average nucleotide identity and digital DNA-DNA hybridization values between strain TRM 85114^T and related type Halomonas strains of H. korlensis XK1^T, H. tibetensis pyc13^T, Chromohalobacter salexigens DSM 6768^T, and Halomonas urumqiensis BZ-SZ-XJ27^T were 75.4-88.9% and 22.9-39.2%, respectively. Based on phenotypic, chemotaxonomic, and molecular features, strain TRM 85114^T represents a novel species of the genus Halomonas, for which the name is proposed as Halomonas jincaotanensis sp. nov.. The type strain is TRM 85114^T (CCTCC AB 2021006^T = LMG 32311^T). The amount of 1-naphthylamine degradation by strain TRM 85114^T reached up to 32.0 mg/L in 14 days.

Enhanced biodegradation and valorization of drilling wastewater via simultaneous production of biosurfactants and polyhydroxyalkanoates by Pseudomonas citronellolis SJTE-3

Pseudomonas citronellolis SJTE-3 was isolated as a highly efficient microorganism for biodegradation and valorization of drilling fluids (DF) wastewater. The strain metabolised DF and oily mud exhibiting up to 93%, 86%, 85% and 88% of chemical oxygen demand (COD), n-dodecane, n-tetradecane and naphthalene removal efficiency respectively. Enhanced bioconversion was enabled through production of biosurfactants that reduced the surface tension of water by 53% and resulted in 43.3% emulsification index (E24), while synthesizing 24% of dry cell weight (DCW) as medium-chain-length polyhydroxyalkanoates (PHA). Expression from the main pathways for alkanes and naphthalene biodegradation as well as biosurfactants and PHA biosynthesis revealed that although the alkanes and naphthalene biodegradation routes were actively expressed even at stationary phase, PHA production was stimulated at late stationary phase and putisolvin could comprise the biosurfactant synthesized. The bioconversion of toxic petrochemical residues to added-value thermoelastomers and biosurfactants indicate the high industrial significance of P. citronellolis SJTE-3.

Shifting from Conventional to Organic Filter Media in Wastewater Biofiltration Treatment: A Review

Biofiltration is a promising wastewater treatment green technology employed to remove various types of pollutants. The efficiency of biofiltration relies on biofilm, and its performance is significantly influenced by various factors such as dissolved oxygen concentration, organic loading rate, hydraulic retention time, temperature, and filter media selection. The existing biofilters utilize conventional media such as gravel, sand, anthracite, and many other composite materials. The material cost of these conventional filter materials is usually higher compared to using organic waste materials as the filter media. However, the utilization of organic materials as biofilter media has not been fully explored and their potential in terms of physicochemical properties to promote biofilm growth is lacking in the literature. Therefore, this review critically discusses the potential of shifting conventional filter media to that of organic in biofiltration wastewater treatment, focusing on filtration efficiency-influenced factors, their comparative filtration performance, advantages, and disadvantages, as well as challenges and prospective areas of organic biofilter development.

Potential of Carica papaya Seed-Derived Bio-Coagulant to Remove Turbidity from Polluted Water Assessed through Experimental and Modeling-Based Study

It is important to develop renewable bio-coagulants to treat turbid water and efficient use of these bio-coagulants requires process optimization to achieve robustness. This study was conducted to optimize the coagulation process using bio-coagulant of deshelled Carica papaya seeds by employing response surface methodology (RSM). This bio-coagulant was extracted by a chemical-free solvent. The experiments were conducted using the Central Composite Design (CCD). Initially, the functional groups and protein content of the bio-coagulant were analyzed. The Fourier Transform Infrared Spectroscopy analysis showed that the bio-coagulant contained OH, C=O and C-O functional groups, which enabled the protein to become polyelectrolyte. The highest efficiency of the bio-coagulant was obtained at dosage of 196 mg/L, pH 4.0 and initial turbidity of 500 NTU. At the optimum conditions, the bio-coagulant achieved 88% turbidity removal with a corresponding 83% coagulation activity. These findings suggested that the deshelled Carica papaya seeds have potential as a promising bio-coagulant in treating the polluted water.