Isolation and Characterization of Bacteria from Refinery Effluent for Degradation of Petroleum Crude Oil in Seawater

Microbial communities in petroleum refinery effluents and their complex functions

Petroleum refinery effluents (PRE) are a significant cause of pollution. It contains toxic compounds such as total petroleum hydrocarbons (TPH), and polycyclic aromatic hydrocarbons (PAHs), as well as heavy metals. They show a huge threat facing the aquaculture habitats, human health, and the environment if they are not treated before discharging into the environment. Physical and chemical procedures are used to treat hydrocarbon pollution in PRE, but these techniques often result in the formation of hazardous by-products during the remediation process. However, PRE contains various microbial communities, including bacteria, yeast, microalgae, and fungi. The bioremediation and biodegradation of oil contaminants are the primary functions of these microbial communities. However, these microorganisms can perform various additional functions including but not limited to heavy metals removal, production of biosurfactants, and nitrogen fixation. This review contributes to the comprehension of natural microbial communities and their complex functions in petroleum refinery effluents. Understanding microbial communities would facilitate the advancement of innovative biotechnology aimed at treating PRE, improving bioremediation processes, and potentially transforming PRE into valuable bio-products. Moreover, it assists in determining the most effective bioaugmentation strategy to enhance biodegradation and bioremediation in PRE. The review highlights the potential for sustainable green approaches using microbial communities to replace toxic chemical therapies and expensive physical treatments in the future.

Biochar-bacteria-plant combined potential for remediation of oil-contaminated soil

Oil pollution is a common type of soil organic pollution that is harmful to the ecosystem. Bioremediation, particularly microbe-assisted phytoremediation of oil-contaminated soil, has become a research hotspot in recent years. In order to explore more appropriate bioremediation strategies for soil oil contamination and the mechanism of remediation, we compared the remediation effects of three plants when applied in combination with a microbial agent and biochar. The combined remediation approach of Tagetes erecta, microbial agent, and biochar exhibited the best plant growth and the highest total petroleum hydrocarbons degradation efficiency (76.60%). In addition, all of the remediation methods provided varying degrees of restoration of carbon and nitrogen contents of soils. High-throughput sequencing found that microbial community diversity and richness were enhanced in most restored soils. Some soil microorganisms associated with oil degradation and plant growth promotion such as Cavicella, C1_B045, Sphingomonas, MND1, Bacillus and Ramlibacter were identified in this study, among which Bacillus was the major component in the microbial agent. Bacillus was positively correlated with all soil remediation indicators tested and was substantially enriched in the rhizosphere of T. erecta. Functional gene prediction of the soil bacterial community based on the KEGG database revealed that pathways of carbohydrate metabolism and amino acid metabolism were up-regulated during remediation of oil-contaminated soils. This study provides a potential method for efficient remediation of oil-contaminated soils and thoroughly examines the biochar-bacteria-plant combined remediation mechanisms of oil-contaminated soil, as well as the combined effects from the perspective of soil bacterial communities.

Biodegradation of benzo(a)pyrene by Pseudomonas strains, isolated from petroleum refinery effluent: Degradation, inhibition kinetics and metabolic pathway

Benzo(a)pyrene, a five-ring polyaromatic hydrocarbon, originating from coal tar, crude oil, tobacco, grilled foods, car exhaust etc, is highly persistent in the environment. It has been classified as a Group I carcinogen, as on its ingestion in human body, diol epoxide metabolites are generated, which bind to DNA causing mutations and eventual cancer. Among various removal methods, bioremediation is most preferred as it is a sustainable approach resulting in complete mineralization of benzo(a)pyrene. Therefore, in this study, biodegradation of benzo(a)pyrene was performed by two strains of Pseudomonas, i. e WDE11 and WD23, isolated from refinery effluent. Maximum benzo(a)pyrene tolerance was 250 mg/L and 225 mg/L against Pseudomonas sp. WD23 and Pseudomonas sp. WDE11 correspondingly. Degradation rate constants varied between 0.0468 and 0.0513/day at 50 mg/L with half-life values between 13.5 and 14.3 days as per first order kinetics, while for 100 mg/L, the respective values varied between 0.006 and 0.007 L/mg. day and 15.28-16.67 days, as per second order kinetics. The maximum specific growth rate of strains WDE11 and WD23 was 0.3512/day and 0.38/day accordingly, while concentrations over 75 mg/L had an inhibitory effect on growth. Major degradation metabolites were identified as dihydroxy-pyrene, naphthalene-1,2-dicarboxylic acid, salicylic acid, and oxalic acid, indicating benzo(a)pyrene was degraded via pyrene intermediates by salicylate pathway through catechol meta-cleavage. The substantial activity of the catechol 2,3 dioxygenase enzyme was noted during the benzo(a)pyrene metabolism by both strains with minimal catechol 1,2 dioxygenase activity. This study demonstrates the exceptional potential of indigenous Pseudomonas strains in complete metabolism of benzo(a)pyrene.

Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites

Kerosene is widely used in Ethiopia as a household fuel (for lighting and heating), as a solvent in paint and grease, and as a lubricant in glass cutting. It causes environmental pollution and escorts to loss of ecological functioning and health problems. Therefore, this research was designed to isolate, identify, and characterize indigenous kerosene-degrading bacteria that are effective in cleaning ecological units that have been contaminated by kerosene. Soil samples were collected from hydrocarbon-contaminated sites (flower farms, garages, and old-aged asphalt roads) and spread-plated on mineral salt medium (Bushnell Hass Mineral Salts Agar Medium: BHMS), which consists of kerosene as the only carbon source. Seven kerosene-degrading bacterial species were isolated, 2 from flower farms, 3 from garage areas, and 2 from asphalt areas. Three genera from hydrocarbon-contaminated sites were identified, including Pseudomonas, Bacillus, and Acinetobacter using biochemical characterization and the Biolog database. Growth studies in the presence of various concentrations of kerosene (1% and 3% v/v) showed that the bacterial isolates could metabolize kerosene as energy and biomass. Thereby, a gravimetric study was performed on bacterial strains that proliferated well on a BHMS medium with kerosene. Remarkably, bacterial isolates were able to degrade 5% kerosene from 57.2% to 91% in 15 days. Moreover, 2 of the most potent isolates, AUG2 and AUG1, resulted in 85% and 91% kerosene degradation, respectively, when allowed to grow on a medium containing kerosene. In addition, 16S rRNA gene analysis indicated that strain AAUG1 belonged to Bacillus tequilensis, whereas isolate AAUG showed the highest similarity to Bacillus subtilis. Therefore, these indigenous bacterial isolates have the potential to be applied for kerosene removal from hydrocarbon-contaminated sites and the development of remediation approaches.

Characterization of biosurfactant produced in response to petroleum crude oil stress by Bacillus sp. WD22 in marine environment

Bacillus sp. WD22, previously isolated from refinery effluent, degraded 71% of C8 hydrocarbons present in 1.0% v/v PCO in seawater (control medium), which reduced to 16.3%, on addition of yeast extract. The bacteria produced a biosurfactant in both media, whose surface was observed to be amorphous in nature under FESEM-EDAX analysis. The biosurfactant was characterized as a linear surfactin by LCMS and FT-IR analysis. The critical micelle concentration was observed as 50 mg/L and 60 mg/L at which the surface tension of water was reduced to 30 mN/m. Purified biosurfactant could emulsify petroleum-based oils and vegetable oils effectively and was stable at all tested conditions of pH, salinity and temperature up to 80 °C. The biosurfactant production was found to be mixed growth associated in control medium, while it was strictly growth associated in medium with yeast extract as studied by the Leudeking-Piret model.

Biodegradation kinetics and metabolism of Benzo(a)fluorene by Pseudomonas strains isolated from refinery effluent

The final sinkers of polyaromatic hydrocarbons are water sources, where they undergo bioaccumulation and biomagnification, leading to adverse mutagenic, carcinogenic, and teratogenic effects on exposure in flora, fauna, and humans. Two indigenous strains, Pseudomonas sp. WDE11 and Pseudomonas sp. WD23, isolated from refinery effluent, degraded over 97.5% of benzo(a)fluorene (10 mg/L) in 7 days. On growth at concentration dependent amounts (50 mg/L and 100 mg/L), the degradation reduced to approximately 90% and 80% respectively in 56 days. Degradation kinetics was concentration dependent, as degradation followed first-order and second-order kinetics for 50 mg/L and 100 mg/L respectively. The half-life for degradation of benzo(a)fluorene ranged between 11.64 - 12.26 days and 13.11-14.5 days for strains WDE11 and WD23 respectively. The values of Andrew-Haldane kinetic parameters i.e. μ_max, K_s, and K_i were 0.306 day^-1, 11.11 mg/L, and 120.41 mg/L for strain WDE11 respectively, while for strain WD23, the respective values were 0.312 day^-1, 9.97 mg/L, and 152 mg/L. Degradation metabolites were identified by their MS patterns as 3,4-dihydroxy fluorene, 2-(1-oxo-2,3-dihydro-1H-inden-2-yl) acetic acid, 3,4-dihydrocoumarin, salicylic acid, catechol, and oxalic acid. Metabolic pathway of degradation constructed, revealed that benzo(a)fluorene was metabolized via the formation of fluorene, further metabolized by salicylate pathway forming catechol. The catechol formed was degraded into simpler metabolites by meta-cleavage pathway, which was validated by catechol 2,3 dioxygenase enzyme activity.

Nitrogen dependence of rhamnolipid mediated degradation of petroleum crude oil by indigenous Pseudomonas sp. WD23 in seawater

Effect of oil spills on living forms demands for safe, ecofriendly and cost-effective methods to repair the damage. Pseudomonads have exceptional tolerance to xenobiotics and can grow at varied environmental conditions. This study aims at biosurfactant mediated degradation of petroleum crude oil by an indigenous Pseudomonas sp. WD23 in sea water. Pseudomonas sp. WD23 degraded 34% of petroleum crude oil (1.0% v/v) on supplementation of yeast extract (0.05 g/L) with glucose (1.0 g/L) in seawater. The strain produced a biosurfactant which was confirmed as a rhamnolipid (lipid: rhamnose 1:3.35) by FT-IR, LCMS and quantitative analysis. Produced rhamnolipid had low CMC (20.0 mg/L), emulsified petroleum oils (75-80%) and had high tolreance to varied conditions of pH, temperature and ionic strength. OFAT studies were performed to analyse the effect of petroleum crude oil, glucose, inoculum, yeast extract, pH, agitation speed and incubation time on degradation by Pseudomonas sp. WD23. Petroleum crude oil and glucose had significant effect on biodegradation, rhamnolipid production and growth, further optimized by central composite design. At optimum conditions of 3.414% v/v PCO and 6.53 g/L glucose, maximum degradation of 81.8 ± 0.67% was observed at pH 7.5, 100 RPM, 15.0% v/v inoculum in 28 days, with a 3-fold increase in biodegradation. GCMS analysis revealed degradation (86-100%) of all low and high molecular weight hydrocarbons present in petroleum crude oil. Hence, the strain Pseudomonas sp. WD23 can be effectively developed for management of oil spills in seas and oceans due to its excellent degradation abilities.

A critical review of oil spills in the Niger Delta aquatic environment: causes, impacts, and bioremediation assessment

The Niger Delta region in South-South Nigeria, on Africa's West Coast, is densely populated. The region, which contains a substantial stock of crude oil and natural gas, has been nicknamed "the engine room" for Nigeria's economic development and progress. It is responsible for up to 90% of the country's economic growth (or gross domestic product/GDP). The region has multiple ecosystems, such as the aquatic environment, that are critical to the survival of the area's various habitats and living species. However, the same region has witnessed unjustifiable environmental pollution arising from oil activities over the years of exploration and production which has orchestrated negative consequences on the Niger Delta ecosystem. This has led to extended negative consequences on natural resources, which also have detrimental repercussions psychologically, ecologically, socially, economically, and physically which, in turn, impacts the overall health of the affected individuals. This write-up provides an overview of the major drivers of the oil leakage in Nigeria's Niger Delta ecosystem as well as the major impacts on the environment. It will also analyze numerous means of remediation in use and extend such for a more inclusive and productive option. Moreover, this review offers key measures that may help to maintain long-term policies for reducing adverse implications and increasing the living standard for the Niger Delta area's affected communities.

Microbial valorization of underutilized and nonconventional waste streams

The growing burden of waste disposal coupled with natural resource scarcity has renewed interest in the remediation, valorization, and/or repurposing of waste. Traditional approaches such as composting, anaerobic digestion, use in fertilizers or animal feed, or incineration for energy production extract very little value out of these waste streams. In contrast, waste valorization into fuels and other biochemicals via microbial fermentation is an area of growing interest. In this review, we discuss microbial valorization of nonconventional, aqueous waste streams such as food processing effluents, wastewater streams, and other industrial wastes. We categorize these waste streams as carbohydrate-rich food wastes, lipid-rich wastes, and other industrial wastes. Recent advances in microbial valorization of these nonconventional waste streams are highlighted, along with a discussion of the specific challenges and opportunities associated with impurities, nitrogen content, toxicity, and low productivity.