Rhamnolipids Produced by Indigenous Acinetobacter junii from Petroleum Reservoir and its Potential in Enhanced Oil Recovery

Recent advances in Emulsan production, purification, and application: Exploring bioemulsifiers unique potentials

Bioemulsifiers are compounds produced by microorganisms that reduce the interfacial forces between hydrophobic substances and water. Due to their potential in the pharmaceutical and food industries and their efficiency in oil spill remediation, they have been the subject of study in the scientific community while being safe, biodegradable, and sustainable compared to synthetic options. These biomolecules have high molecular weight and polymeric structures, distinguishing them from traditional biosurfactants. Emulsan, a bioemulsifier exopolysaccharide, is produced by Acinetobacter strains and is highly efficient in forming stable emulsions. Its low toxicity and high potential as an emulsifying agent promote its application in pharmaceutical and food industries as a drug-delivery vehicle and emulsion stabilizer. Due to the high environmental impact of oil spills, bioemulsifiers have great potential for environmental applications, such as bioremediation. This unique feature gives them a distinct mechanism of action in forming emulsions, resulting in minimal environmental impact. A better understanding of these aspects can improve the use of bioemulsifiers and environmental remediation in various industries. This review will discuss the production and characterization of Emulsan, focusing on recent advancements in cultivation conditions, purification techniques, compound identification, and ecotoxicity.

Biosurfactant and biopolymer producing microorganisms from West Kazakhstan oilfield

Microbiological enhanced oil recovery (MEOR) uses indigenous or exogenous microorganisms and nutrients to enhance oil production through synthesis of metabolites reducing oil viscosity and surface tension. In order to find bacteria suitable for MEOR, we studied 26 isolates from wells in the Akingen oilfield in West Kazakhstan. Six of them were selected for further analysis based on their ability to reduce surface tension to less than 40 mN/m, with the A9 isolate exhibiting tension reduction values of 32.76 ± 0.3 mN/m. Based on the morphological features, biochemical activities, and the 16S rRNA gene, the isolates were classified to the Bacillus subtilis group. In the phylogenetic analysis the isolates grouped into two main clusters. Genes encoding the surfactin synthetase subunits were found in A2, A8, A9, A12, PW2, only the PW2 strain had lchAA encoding lichenysin, while sacB encoding levan was noted in A2, A8, A9, and A12. The expression of srfAB, srfAC, and sacB tested with qPCR varied among strains. Nevertheless, whereas temperature moderately affects the expression level, with the highest level recorded at 40 °C, salinity significantly impacts the expression of the genes encoding biosurfactants. B. subtilis strains isolated in the study, especially A9, are promising for microbial-enhanced oil recovery.

Sustainable production of biosurfactants via valorisation of industrial wastes as alternate feedstocks

Globally, the rapid increase in the human population has given rise to a variety of industries, which have produced a variety of wastes. Due to their detrimental effects on both human and environmental health, pollutants from industry have taken centre stage among the various types of waste produced. The amount of waste produced has therefore increased the demand for effective waste management. In order to create valuable chemicals for sustainable waste management, trash must be viewed as valuable addition. One of the most environmentally beneficial and sustainable choices is to use garbage to make biosurfactants. The utilization of waste in the production of biosurfactant provides lower processing costs, higher availability of feedstock and environmental friendly product along with its characteristics. The current review focuses on the use of industrial wastes in the creation of sustainable biosurfactants and discusses how biosurfactants are categorized. Waste generation in the fruit industry, agro-based industries, as well as sugar-industry and dairy-based industries is documented. Each waste and wastewater are listed along with its benefits and drawbacks. This review places a strong emphasis on waste management, which has important implications for the bioeconomy. It also offers the most recent scientific literature on industrial waste, including information on the role of renewable feedstock for the production of biosurfactants, as well as the difficulties and unmet research needs in this area.

Bacterial and Archaeal Community Distribution in Oilfield Water Re-injection Facilities and the Influences from Microorganisms in Injected Water

Water flooding is widely employed for oil production worldwide. However, there has never been a systematic investigation of the microbial communities occurring in oilfield water re-injection facilities. Here, we investigated the distribution of bacterial and archaeal communities in water re-injection facilities of an oilfield, and illustrated the combined influences of environmental variation and the microorganisms in injected water on the microbial communities. Bacterial communities from the surface injection facilities were dominated by aerobic or facultative anaerobic Betaproteobacteria, Alphaproteobacteria, and Flavobacteria, whereas Clostridia, Deltaproteobacteria, Anaerolineae, and Synergistia predominated in downhole of the injection wells, and Gammaproteobacteria, Betaproteobacteria, and Epsilonproteobacteria predominated in the production wells. Methanosaeta, Methanobacterium, and Methanolinea were dominant archaea in the injection facilities, while Methanosaeta, Methanomethylovorans, and Methanoculleus predominated in the production wells. This study also demonstrated that the microorganisms in injected water could be easily transferred from injection station to wellheads and downhole of injection wells, and environmental variation and diffusion-limited microbial transfer resulted from formation filtration were the main factors determining microbial community assembly in oil-bearing strata. The results provide novel information on the bacterial and archaeal communities and the underlying mechanisms occurring in oilfield water re-injection facilities, and benefit the development of effective microbiologically enhanced oil recovery and microbiologically prevented reservoir souring programs.

Surface-Active Compounds Produced by Microorganisms: Promising Molecules for the Development of Antimicrobial, Anti-Inflammatory, and Healing Agents

Surface-active compounds (SACs), biomolecules produced by bacteria, yeasts, and filamentous fungi, have interesting properties, such as the ability to interact with surfaces as well as hydrophobic or hydrophilic interfaces. Because of their advantages over other compounds, such as biodegradability, low toxicity, antimicrobial, and healing properties, SACs are attractive targets for research in various applications in medicine. As a result, a growing number of properties related to SAC production have been the subject of scientific research during the past decade, searching for potential future applications in biomedical, pharmaceutical, and therapeutic fields. This review aims to provide a comprehensive understanding of the potential of biosurfactants and emulsifiers as antimicrobials, modulators of virulence factors, anticancer agents, and wound healing agents in the field of biotechnology and biomedicine, to meet the increasing demand for safer medical and pharmacological therapies.

Optimization and characterization of biosurfactant produced by indigenous Brevibacillus borstelensis isolated from a low permeability reservoir for application in MEOR

Biosurfactants are expected to be a key factor for microbial enhanced oil recovery (MEOR). In this study, we described the novel biosurfactant-producing strain Brevibacillus borstelensis YZ-2 isolated from a low permeability oil reservoir. We purified and characterized the biosurfactants produced by this YZ-2 strain via thin-layer chromatography and MALDI-TOF-MS, revealing them to be fengycins. We additionally used a Box–Behnken design approach to optimize fermentation conditions in order to maximize the biosurfactants production. Core flooding experiments showed that biosurfactants produced by YZ-2 can significantly enhance crude oil recovery. Micro-model tests showed that emulsification and IFT reduction was the main EOR mechanism of the YZ biosurfactant in the oil wet model. In summary, these findings highlight the potential of Brevibacillus borstelensis YZ-2 and its metabolites for MEOR.

Biosurfactants are expected to be a key factor for microbial enhanced oil recovery (MEOR).

Comparison of mono-rhamnolipids and di-rhamnolipids on microbial enhanced oil recovery (MEOR) applications

Rhamnolipids (RMLs) have more effectiveness for specific uses according to their homologue proportions. Thus, the novelty of this work was to compare mono-RMLs and di-RMLs physicochemical properties on microbial enhanced oil recovery (MEOR) applications. For this, RML produced by three strains of Pseudomonas aeruginosa containing different homologues proportion were used: a mainly mono-RMLs producer (mono-RMLs); a mainly di-RMLs producer (di-RMLs), and the other one that produces relatively balanced amounts of mono-RML and di-RML homologues (mono/di-RML). For mono-RML, the most abundant molecules were Rha-C₁₀ C₁₀ (m/z 503.3), for di-RML were RhaRha-C₁₀ C₁₀ (m/z 649.4) and for Mono/di-RML were Rha-C₁₀ C₁₀ (m/z 503.3) and RhaRha-C₁₀ C₁₀ (m/z 649.4). All RMLs types presented robustness under high temperature and variation of salinity and pH, and high ability for oil displacement, foam stability, wettability reversal and were classified as safe for environment according to the European Union Directive No. 67/548/EEC. For all these properties, it was observed a highlight for mono-RML. Mono-RML presented the lowest surface tension (26.40 mN/m), interfacial tension (1.14 mN/m), and critical micellar concentration (CMC 27.04 mg/L), the highest emulsification index (EI₂₄ 100%) and the best wettability reversal (100% with 25 ppm). In addition, mono-RML showed the best acute toxicity value (454 mg/L), making its application potential even more attractive. Based on the results, it was concluded that all RMLs homologues studied have potential for MEOR applications. However, results showed that mono-RML stood out and have the best mechanism of oil incorporation in micelles due their most effective surface-active physicochemical features.

Biodegradation of aliphatic and polycyclic aromatic hydrocarbons by the thermophilic bioemulsifier-producing Aeribacillus pallidus strain SL-1

The utilization of thermophilic hydrocarbon-degrading microorganisms is a suitable strategy for improving biodegradation of petroleum hydrocarbons and PAHs, as well as enhancing oil recovery from high-temperature reservoirs. In this study, the thermophilic strain Aeribacillus pallidus SL-1 was evaluated for the biodegradation of crude oil and PAHs at 60 °C. Strain SL-1 was found to preferentially degrade short-chain n-alkanes (<C17) and aromatic hydrocarbons from crude oil. The highest degradation rate of 84% was obtained with 1000 mg/l naphthalene as sole carbon source. Additionally, the strain was able to degrade 80% of phenanthrene (200 mg/l) and 50% of pyrene (50 mg/l) within 5 days at 60 °C. The SL-bioemulsifier produced by strain SL-1 was identified as a glycoprotein with stable emulsifying activity over a wide range of environmental conditions. Chemical composition studies exhibited that the SL-bioemulsifier consisted of polysaccharides (65.6%) and proteins (13.1%), among them, proteins were the major emulsifying functional substrates. Furthermore, the SL-bioemulsifier was able to enhance the solubility of PAHs. Thus, the bioemulsifier-producing strain SL-1 has great potential for applications in high-temperature bioremediation.

Low-Abundance Dietzia Inhabiting a Water-Flooding Oil Reservoir and the Application Potential for Oil Recovery

With the development of molecular ecology, increasing low-abundance microbial populations were detected in oil reservoirs. However, our knowledge about the oil recovery potential of these populations is lacking. In this study, the oil recovery potential of low-abundance Dietzia that accounts for less than 0.5% in microbial communities of a water-flooding oil reservoir was investigated. On the one hand, Dietzia sp. strain ZQ-4 was isolated from the water-flooding reservoir, and the oil recovery potential was evaluated from the perspective of metabolisms and oil-displacing test. On the other hand, the strain has alkane hydroxylase genes alkB and P450 CYP153 and can degrade hydrocarbons and produce surfactants. The core-flooding test indicated that displacing fluid with 2% ZQ-4 fermentation broth increased 18.82% oil displacement efficiency, and in situ fermentation of ZQ-4 increased 1.97% oil displacement efficiency. Furthermore, the responses of Dietzia in the reservoir accompanied by the nutrient stimulation process was investigated and showed that Dietzia in some oil production wells significantly increased in the initial phase of nutrient injection and sharply decreased along with the continuous nutrient injection. Overall, this study indicates that Dietzia sp. strain has application potential for enhancing oil recovery through an ex situ way, yet the ability of oil recovery in situ based on nutrient injection is limited.

Designer bioemulsifiers based on combinations of different polysaccharides with the novel emulsifying esterase AXE from Bacillus subtilis CICC 20034

Background

Bioemulsifiers are surface-active compounds, which exhibit advantages including low toxicity, higher biodegradability and biocompatibility over synthetic chemical surfactants. Despite their potential benefits, some obstacles impede the practical applications of bioemulsifiers, including low yields and high purification costs. Here, we aimed to exploit a novel protein bioemulsifier with efficient emulsifying activity and low-production cost, as well as proposed a design-bioemulsifier system that meets different requirements of industrial emulsification in the most economical way.

Results

The esterase AXE was first reported for its efficient emulsifying activity and had been studied for possible application as a protein bioemulsifier. AXE showed an excellent emulsification effect with different hydrophobic substrates, especially short-chain aliphatic and benzene derivatives, as well as excellent stability under extreme conditions such as high temperature (85 °C) and acidic conditions. AXE also exhibited good stability over a range of NaCl, MgSO₄, and CaCl₂ concentrations from 0 to 1000 mM, and the emulsifying activity even showed a slight increase at salt concentrations over 500 mM. A design-bioemulsifier system was proposed that uses AXE in combination with a variety of polysaccharides to form efficient bioemulsifier, which enhanced the emulsifying activity and further lowered the concentration of AXE needed in the complex.

Conclusions

AXE showed a great application potential as a novel bioemulsifier with excellent emulsifying ability. The AXE-based-designer bioemulsifier could be obtained in the most economical way and open broad new fields for low-cost, environmentally friendly bioemulsifiers.

Stable bioemulsifiers are produced by Acinetobacter bouvetii UAM25 growing in different carbon sources

Acinetobacter species are identified as producing surface-active and emulsifying molecules known as bioemulsifiers. Production, characterization and stability of bioemulsifiers produced by Acinetobacter bouvetii UAM25 were studied. A. bouvetii UAM25 grew in three different carbon and energy sources: ethanol, a glycerol-hexadecane mixture and waste cooking oil in an airlift bioreactor, showing that bioemulsifier production was growth associated. The three purified bioemulsifiers were lipo-heteropolysaccharides of high molecular weight (4866 ± 533 and 462 ± 101 kDa). The best carbon source and energy for bioemulsifier production was wasted cooking oil, with a highest emulsifying capacity (76.2 ± 3.5 EU mg^-1) as compared with ethanol (46.6 ± 7.1 EU mg^-1) and the glycerol-hexadecane mixture (49.5 ± 4.2 EU mg^-1). The three bioemulsifiers in our study displayed similar macromolecular structures, regardless of the nature (hydrophobic or hydrophilic) of the carbon and energy source. Bioemulsifiers did not decrease surface tension, but the emulsifying capacity of all of them was retained under extreme variation in salinity (0-50 g NaCl L^-1), pH (3-10) and temperature (25-121 °C), indicative of remarkable stability. These findings contribute to understanding of the relationship between: production, physical properties, chemical composition and stability of bioemulsifiers for their potential applications in biotechnology, such as bioremediation of hydrocarbon-contaminated soil and water.