Solid inoculants as a practice for bioaugmentation to enhance bioremediation of hydrocarbon contaminated areas

Microbial response to a port fuel spill: Community dynamics and potential for bioremediation

Following a fuel leakage inside a Portuguese maritime port, we conducted parallel 30-day experiments using contaminated seawater and fuel, sampled five days after the incident. This study aimed to (i)survey the native microbial community response to the spilled fuel and (ii)evaluate the efficacy of bioremediation, both biostimulation and bioaugmentation with a lyophilized bacterial consortium (Rhodococcus erythropolis, Pseudomonas sp.), in accelerating hydrocarbon degradation. Metabarcoding analysis revealed a shift in microbial communities, with increased abundance of hydrocarbon-degraders (e.g. Alcanivorax, Thalassospira). Ninety-five hydrocarbonoclastic bacteria were isolated, including key groups from the enriched communities. The lyophilized bacteria added in bioaugmentation, enhanced the abundance of hydrocarbon-degraders over time and were recovered throughout time. Bioremediation treatments favoured biodegradation, achieving over 60 % removal of total petroleum hydrocarbons after 15 days, contrasting with natural attenuation where almost no TPH was removed. This work highlights the potential of bioremediation technologies to accelerate hydrocarbon-degrading activity, for oil spills inside ports.

Thermally enhanced bioremediation: A review of the fundamentals and applications in soil and groundwater remediation

Thermally enhanced bioremediation (TEB), a new concept proposed in recent years, explores the combination of thermal treatment and bioremediation to address the challenges of the low efficiency and long duration of bioremediation. This study presented a comprehensive review regarding the fundamentals of TEB and its applications in soil and groundwater remediation. The temperature effects on the bioremediation of contaminants were systematically reviewed. The thermal effects on the physical, chemical and biological characteristics of soil, and the corresponding changes of contaminants bioavailability and microbial metabolic activities were summarized. Specifically, the increase in temperature within a suitable range can proliferate enzymes enrichment, extracellular polysaccharides and biosurfactants production, and further enhancing bioremediation. Furthermore, a systematic evaluation of TEB applications by utilizing traditional in situ heating technologies, as well as renewable energy (e.g., stored aquifer thermal energy and solar energy), was provided. Additionally, TEB has been applied as a biological polishing technology post thermal treatment, which can be a cost-effective method to address the contaminants rebounds in groundwater remediation. However, there are still various challenges to be addressed in TEB, and future research perspectives to further improve the basic understanding and applications of TEB for the remediation of contaminated soil and groundwater are presented.

Biodegradation Potential of Bacillus sp. PAH-2 on PAHs for Oil-Contaminated Seawater

Microbial degradation is a useful tool for inhibiting or preventing polycyclic aromatic hydrocarbons (PAHs) widely distributed in marine environment after oil spill accidents. This study aimed to evaluate the potential and diversity of bacteria Bacillus sp. PAH-2 on Benzo (a) anthracene (BaA), Pyrene (Pyr), and Benzo (a) pyrene (BaP), their composite system, aromatic components system, and crude oil. The seven-day degradation rates against BaA, Pyr, and BaP were 20.6%, 12.83%, and 17.49%, respectively. Further degradation study of aromatic components demonstrated PAH-2 had a high degradation rate of substances with poor stability of molecular structure. In addition, the degradation of PAHs in crude oil suggested PAH-2 not only made good use of PAHs in such a more complex structure of pollutants but the saturated hydrocarbons in the crude oil also showed a good application potential.

Crude oil exploration in Africa: socio-economic implications, environmental impacts, and mitigation strategies

Crude oil exploration is a source of significant revenue in Africa via trade and investment since its discovery in the mid-19th Century. Crude oil has bolstered the continent's economy and improved the wellbeing of the citizenry. Historically, Africa has suffered from conflicts due to uneven redistribution of crude oil revenue and severe environmental pollution. Advancements in geophysical survey techniques, such as magnetic and gravity methods, to seismic methods, have made the commercial exploration of crude oil possible for some other countries in Africa apart from Nigeria, Angola, Algeria, Libya, and Egypt. The occurrence of organic-rich, oil-prone Type I, II, and mixed II/III kerogens in sedimentary basins and entrapment within reservoir rocks with intrinsic petrophysical properties are majorly responsible for the large deposits of hydrocarbon in Africa. The unethical practices by some multinational oil corporations have resulted in social movements against them by host communities and human rights groups. The unscrupulous diversion of public funds, award of oil blocks, and production rights to certain individuals have impaired economic growth in Africa. The over-dependence on crude oil revenues has caused the economic recession in oil-producing countries due to plummeting oil prices and global pandemic. Most host communities of crude oil deposits suffer from a lack of infrastructure, arable soils, clean water, and their functioning capabilities are violated by crude oil exploratory activities, without adequate compensations and remedial actions taken by oil companies and the government. Thus, this review examines crude oil exploration in Africa and provides insight into the environmental and socio-economic implications of crude oil exploration in Africa. Furthermore, this report highlights some recommendations that may ensure ethical and sustainable practices toward minimizing negative impacts and improving the quality of life in affected communities.

Bioremediation of Petroleum Hydrocarbons in Seawater: Prospects of Using Lyophilized Native Hydrocarbon-Degrading Bacteria

This work aimed to develop a bioremediation product of lyophilized native bacteria to respond to marine oil spills. Three oil-degrading bacterial strains (two strains of Rhodococcus erythropolis and one Pseudomonas sp.), isolated from the NW Portuguese coast, were selected for lyophilization after biomass growth optimization (tested with alternative carbon sources). Results indicated that the bacterial strains remained viable after the lyophilization process, without losing their biodegradation potential. The biomass/petroleum ratio was optimized, and the bioremediation efficiency of the lyophilized bacterial consortium was tested in microcosms with natural seawater and petroleum. An acceleration of the natural oil degradation process was observed, with an increased abundance of oil-degraders after 24 h, an emulsion of the oil/water layer after 7 days, and an increased removal of total petroleum hydrocarbons (47%) after 15 days. This study provides an insight into the formulation and optimization of lyophilized bacterial agents for application in autochthonous oil bioremediation.

Bacteria, Fungi and Microalgae for the Bioremediation of Marine Sediments Contaminated by Petroleum Hydrocarbons in the Omics Era

Petroleum hydrocarbons (PHCs) are one of the most widespread and heterogeneous organic contaminants affecting marine ecosystems. The contamination of marine sediments or coastal areas by PHCs represents a major threat for the ecosystem and human health, calling for urgent, effective, and sustainable remediation solutions. Aside from some physical and chemical treatments that have been established over the years for marine sediment reclamation, bioremediation approaches based on the use of microorganisms are gaining increasing attention for their eco-compatibility, and lower costs. In this work, we review current knowledge concerning the bioremediation of PHCs in marine systems, presenting a synthesis of the most effective microbial taxa (i.e., bacteria, fungi, and microalgae) identified so far for hydrocarbon removal. We also discuss the challenges offered by innovative molecular approaches for the design of effective reclamation strategies based on these three microbial components of marine sediments contaminated by hydrocarbons.

Microfluidic Based Whole-Cell Biosensors for Simultaneously On-Site Monitoring of Multiple Environmental Contaminants

Monitoring of environmental contaminants serves a vital role in proactive environmental management and pollution control. Research efforts have been centered on the development of robust whole-cell biosensors in recent years. However, data acquisition, multiple contaminants detection and biosafety issues limit the on-site application of such biosensors. Microfluidic system exhibits great potential to face these challenges via coupling biosensors. Here, we prospect a novel microfluidic based whole-cell biosensor (MWCB) for multiplexing monitoring of diverse contaminants, and design strategies to further increase the specificity, sensitivity and accuracy, reduce signal delay and expand shelf life of the proposed MWCB for on-site environmental applications. The development of MWCB demands multidisciplinary cooperation, and the sensing platforms are highly promising for real-world contaminants monitoring.