Strategic implementation of integrated bioaugmentation and biostimulation for efficient mitigation of petroleum hydrocarbon pollutants from terrestrial and aquatic environment

Comparing the effect of applying different types of amendments on carbon emissions and kinetics of degrading total petroleum hydrocarbons in artificial petroleum-contaminated soil

Contamination by spent engine oil represents a significant global environmental challenge as it poses a major hazard to human health, animals, plants, microorganisms, the soil ecosystem, and aquatic ecosystems. This study assumes that some amendments differ significantly in their ability to degrade petroleum hydrocarbons. Therefore, this incubation study was conducted to investigate the effect of different types of inorganic and organic amendments (zeolite, bone char, banana leaves biochar, and wood chips biochar) on carbon emissions (CO2-C) and the kinetics of total petroleum hydrocarbons (TPHC) degradation in artificial petroleum-contaminated soil. These amendments were added to the soil under study at a dose of 3% (w/w). At the end of the incubation period, applying zeolite, bone char, banana leaves biochar, and wood chips biochar to artificial petroleum-contaminated soil significantly reduced cumulative CO2-C emissions compared to the control. The banana leaves biochar significantly decreased TPHC concentrations in artificial petroleum-contaminated soil compared to the control treatment. At the end of the incubation period, adding banana leaves biochar to the soil showed high degradation efficiencies of TPHC which was 36% higher than soil before incubation. The effectiveness of applying amendments used in this experiment on the degradation of TPHC increase was in the order of banana leaves biochar > bone char > wood chips biochar > control > zeolite. The second-order model described the kinetics of total petroleum hydrocarbons better than the first-order model. Banana leaves biochar added to the soil resulted in a significant increase in the degradation rate constant of total petroleum hydrocarbons (k2) compared with the control. A higher k2 value indicates that TPHC degrades more rapidly. The half-life of TPHC degradation in the soil was decreased significantly by adding banana leaves biochar. According to the second-order equation, the half-lives of control, zeolite, bone char, banana leaves biochar, and wood chips biochar were 4.0, 5.3, 2.7, 1.0, and 3.6 years, respectively. The banana leaves biochar amendment might be cheaper and more environmentally friendly than other organic amendments because it has the high potential for carbon sequestration and remediate petroleum-contaminated soil, which would increase the sustainable use of petroleum-contaminated soil leading to preserving the environment.

Bioremediation of petroleum-contaminated soil based on both toxicity risk control and hydrocarbon removal-progress and prospect

Petroleum contamination remains a worldwide issue requiring cost-effective bioremediation techniques. However, establishing a universal bioremediation strategy for all types of oil-polluted sites is challenging. This difficulty arises from the heterogeneity of soil textures, the complexity of oil products, and the variations in local climate and environment across different oil-contaminated regions. Several factors can impede bioremediation efficacy: (i) differences in bioavailability and biodegradability between aliphatic and aromatic fractions of crude oil; (ii) inconsistencies between hydrocarbon removal efficiency and toxicity attenuation during remediation; (iii) varying adverse effect of aliphatic and aromatic fractions on soil microorganisms. This review examines the ecotoxicity risk of petroleum contamination to soil fauna and flora. It also discusses three primary bioremediation strategies: biostimulation with nutrients, bioaugmentation with petroleum degraders, and phytoremediation with plants. Based on current research and state-of-the-art challenges, we highlighted future research scopes should focus on (i) exploring the ecotoxicity differentiation of aliphatic and aromatic fractions of crude oil, (ii) establishing unified risk factors and indicators for evaluating oil pollution toxicity, (iii) determining the fate and transformation of aliphatic and aromatic fractions of crude oil using advanced analytical techniques, and (iv) developing combined bioremediation techniques that improve petroleum removal and ecotoxicity attenuation.

The mechanisms of yeast extracellular metabolites in stimulating microbial degradation of trichloroethylene: Physiological characteristics and omics analysis

The biodegradation of Trichloroethylene (TCE) is limited by low microbial metabolic capacity but can be enhanced through biostimulation strategies. This study explored the physiological effects and potential molecular mechanisms of the yeast Yarrowia lipolytica extracellular metabolites (YEMs) on the degradation of TCE by Acinetobacter LT1. Results indicated that YEMs stimulated the efficiency of strain LT1 by 50.28%. At the physiological level, YEMs exhibited protective effects on cell morphology, reduced oxidative stress, lessened membrane damage, and enhanced energy production and conversion. Analysis of omics results revealed that the regulation of various metabolic pathways by YEMs improved the degradation of TCE. Furthermore, RT-qPCR showed that the genes encoding YhhW protein in TCE stress and YEMs stimulation groups were 1.72 and 3.22 times the control group, respectively. Molecular docking results showed that the conformation of YhhW after binding to TCE changed into a more active form, which enhanced enzyme activity. Therefore, it is speculated that YhhW is the primary degradative enzyme involved in the process of YEMs stimulating strain LT1 to degrade TCE. These results reveal how YEMs induce strain LT1 to enhance TCE degradation.

Influences of extracellular polymeric substances (EPS) recovered from waste sludge on the ability of Jiaozhou Bay to self-remediate of diesel-polluted seawater

The introduction of EPS recovered from waste sludge may have an impact on the process of microbial remediation of oil-contaminated seawater. This study investigated the effect of EPS on the self-remediation capacity of diesel-polluted seawater in Jiaozhou Bay. Hydrocarbon attenuation and microbial activity were monitored in seawater collected from five islands after diesel and N, P addition, with and without EPS, incubated under aerobic conditions. Compared to seawater without EPS, degradation of TPH (total petroleum hydrocarbon) doubled and improved degradation of non-volatile (C16-C24) hydrocarbons to some extent in EPS-added seawater. The introduction of EPS led to changes in microbiota richness and diversity, significantly stimulating the growth of Proteobacteria and Firmicutes phyla or Bacillus and Pseudomonas genera. RT-qPCR analysis indicated EPS caused higher increases in cytochrome P450 gene copies than alkB. Prediction of alkane decay genes from 16S rRNA sequencing data revealed that EPS addition obviously promoted genes related to ethanol dehydrogenation function in the microbial community. Additionally, EPS enhanced the enzymatic activities of alkane hydroxylase, ethanol dehydrogenase, phosphatase and lipase, but increased protease and catalase inconspicuously. The above outlook that environmental sustainability of EPS from waste sludge for diesel-contaminated seawater remediation may provide new perspectives for oil spill bioremediation.

Effects of biodegradation, biotoxicity and microbial community on biostimulation of sulfolane

To evaluate the effectiveness of biostimulation in remediating soil-free groundwater and groundwater with soil, experiments were conducted using soil and groundwater samples that were contaminated with sulfolane. The main objective was to characterize the differences in sulfolane removal efficiency and biotoxicity between in situ soil-free groundwater and groundwater with soil and different concentrations of dissolved oxygen (1 mg/L and 5 mg/L) and various nutrient salts (in situ and spiked). Optimizing the nutrient salt conditions improved the removal efficiency of sulfolane by 1.8-6.5 that under in situ nutrient salt conditions. Controlling the dissolved oxygen concentration enhanced the efficiency of removal of sulfolane by 1.5-4.5 times over that at the simulated in situ dissolved oxygen concentration, suggesting that the degradation of sulfolane by indigenous microorganisms requires nutrient salts more than it requires dissolved oxygen. Biotoxicity data showed that the luminescence inhibition of Aliivibrio fischeri by sulfolane was lower in the biostimulated samples than in the pre-treated samples. Biostimulation reduced the biotoxicity of the treated samples by 42-51%, revealing that it was effective in removing sulfolane and reducing biotoxicity. Microbial community analysis showed that the biostimulation did not change the dominant species in the original in situ community, and increased the proportion of sulfolane-degraders. The outcome of this study can be used to set parameters for the remediation of groundwater that is contaminated by sulfolane in oil refineries.