Biosurfactant-producing Bacteria Research Articles

Isolation and Characterization of Glycolipid Biosurfactant Produced by Marine Bacterium Cobetia marina Strain F1 and Investigation of Antimicrobial and Anti-Biofilm Activity

The marine environment is a rich source of microorganisms producing bioactive compounds, like biosurfactant-producing bacteria that exhibit unique characteristics and functionalities. In this study, we examined glycolipid biosurfactants produced by bacteria that live commensally with marine organisms. We isolated a biosurfactant-producing strain identified as Cobetia marina strain F1, which displayed high hemolytic activity (27 mm), oil spreading ability (4 mm), emulsification index (40%), and decreasing surface tension to 31.3 (mN·m−1). Fourier transform infrared (FT-IR) spectroscopy revealed the glycolipid composition of the biosurfactant. Furthermore, elemental analysis utilizing CHNS and energy-dispersive X-ray spectroscopy (EDS) confirmed the biosurfactant contained carbon, hydrogen, nitrogen, sulfur, chlorine, potassium, oxygen, and additional elements. The critical micelle concentration (CMC) of the crude biosurfactant was determined to be 350 mg·L−1, at which concentration, a decrease in surface tension was observed when the biosurfactant was dissolved in distilled water. Given the presence of impurities in the biosurfactant composition, this observed CMC is considered acceptable. Furthermore, the biosurfactant exhibited significant antimicrobial activity against both Gram-positive and Gram-negative bacterial strains, with the largest zone of inhibition (ZOI) of 27 mm against Pseudomonas aeruginosa. This demonstrates the potential of the biosurfactant to serve as an alternative to novel antibiotic agents. The biosurfactant exhibited considerable inhibition of biofilm formation, disruption of preformed biofilms, and reduced enzymatic activity in bacterial cells following treatment. Moreover, the combination of the biosurfactant and F1 bacterial strain enhanced the degradation of crude oil by 86%, indicating its potential application in environmental remediation. These findings highlight the importance of investigating commensal strains capable to produce biosurfactants for applications in hydrocarbon remediation, overcoming antibiotic resistance, and biofilm disruption.

Molecular characterization of biosurfactant-producing bacteria from a crude oil polluted soil in Nigeria

Most biosurfactant-producing microorganisms are hydrocarbon degraders. The research was conducted to isolate and characterize biosurfactant-producing bacteria from a crude oil polluted soil in Nigeria. Biosurfactant-producing bacteria were isolated from crude oil-polluted soil. Crude oil-polluted soil was collected by random sampling and its physicochemical analysis was done. Bacteria were isolated from the contaminated soil and screened for biosurfactant production. Organisms that showed the ability to produce biosurfactant were identified using morphological, biochemical and molecular methods. The physicochemical parameters of the soil showed a pH 6.9, electrical conductivity of 71.5, 2.55% carbon, 2.016% nitrogen and 5.98% phosphorus. The values of biosurfactant tests showed that organisms S2 and S13 were positive for biosurfactant production. The percentage emulsion indexes of the two selected organisms S2 and S13 were 59.09% and 57.14% respectively. The Blast analysis from the molecular identification showed that the isolated organisms were Gordonia alkanivorans for S2 and Tsukamurella inochensis for S13. This research showed that the isolated biosurfactant-producing bacteria are abundant in the crude oil polluted soil.

Isolation, identification, and characterization of potential biosurfactant-producing bacteria from processing wastewater for the development of eco-friendly green technology

Exploring novel biosurfactants (BS) has become a critical focus in biotechnology research. While BS provides eco-friendly substitutes to chemical surfactants, there is a need to identify high-potential BS-producing bacteria. Currently, the sustainable development of BS-based technologies is hindered by the lack of systematic exploration and understanding of microbial diversity for BS production. This study aims to isolate and identify novel BS isolated from different strains and elucidate their chemical structures for assessing their potential applications. Eleven BS-producing bacteria were isolated from processing wastewater (PWW). The strains were identified by 16S ribotyping and screened for BS production. The produced BS were characterized using Fourier transform infrared and nuclear magnetic resonance spectroscopic techniques. The results indicated that five strains produced a lipopeptide BS, while the other six strains produced glycolipid BS. According to the findings, eleven strains are distributed in eight genera indicating the high bacterial diversity in BS production.

Isolation and Identification of Biosurfactant-Producing Bacteria in An-aerobic Palm Oil Waste Pools at PT. Aek Loba Plantation

Biosurfactant-producing bacteria are bacteria that have alternative energy sources, namely surfactants which contain hydrophilic and hydrophobic groups based on their molecular structure so that they can survive between different polar and hydrogen bonding fluids. Palm oil mill liquid waste is waste in the form of water or liquid, oil and organic solids produced from the processing of palm oil. The purpose of this study was to determine the genera of biosurfactant-producing bacteria found in palm oil wastewater in the an-aerobic pond of PT. Aek Loba plantation and to find out the bacterial species with the highest emulsification index. This study used descriptive methods and identification of bacteria through morphological characterization, gram staining tests and biochemical tests. Bacteria were isolated from palm oil wastewater by dilution method 10-4, 10-5 and 10-6. Bacterial emulsification index is calculated by emulsification test. In this study, 8 biosurfactant-producing bacterial isolates were found, consisting of 2 Proteus genus isolates, 2 Enterobacter genus isolates, 2 Bacillus genus bacterial isolates and 2 Pluralibacter genus isolates. The bacteria that had the highest emulsification index was Pluralibacter gergoviae with an emulsion index of 43% which was identified by molecular testing.

Roles of n-hexadecane in the degradation of dibenzofuran by a biosurfactant-producing bacterium Rhodococcus sp.

The hydrophobic nature of dioxins is a major obstacle to their bioremediation. The present study attempted to improve the bioaccessibility of dioxins in two-phase partitioning bioreactors and activated sludge reactors. Dibenzofuran and n-hexadecane were used as model compounds for dioxins and non-aqueous phase liquids (NAPLs), respectively. First, biosurfactants produced by dioxin-degrading Rhodococcus sp. strain p52 were analyzed. Then, the role of n-hexadecane during the biodegradation of dibenzofuran was evaluated. The results showed that high NAPL ratios (n-hexadecane ≥40 g/L) in the two liquid-phase systems favored dibenzofuran removal, while the cell surface of strain p52 became extremely hydrophobic (>97%), which promoted its adhesion to NAPLs and subsequent transport of dibenzofuran from NAPL to the cells. In addition, a bioaugmented activated sludge reactor with n-hexadecane as the supplemented carbon source could not only facilitate the aerobic granular sludge formation but also improve dibenzofuran removal and the activated sludge settling properties. Simultaneously, conjugative transfer of catabolic plasmids was promoted. This study demonstrated the potential application of strain p52 with NAPLs for the bioremediation of dioxins.

Bioremediation of hydrocarbon by co-culturing of biosurfactant-producing bacteria in microbial fuel cell with Fe2O3-modified anode

The most common type of environmental contamination is petroleum hydrocarbons. Sustainable and environmentally friendly treatment strategies must be explored in light of the increasing challenges of toxic and critical wastewater contamination. This paper deals with the bacteria-producing biosurfactant and their employment in the bioremediation of hydrocarbon-containing waste through a microbial fuel cell (MFC) with Pseudomonas aeruginosa (exoelectrogen) as co-culture for simultaneous power generation. Staphylococcus aureus is isolated from hydrocarbon-contaminated soil and is effective in hydrocarbon degradation by utilizing hydrocarbon (engine oil) as the only carbon source. The biosurfactant was purified using silica-gel column chromatography and characterised through FTIR and GCMS, which showed its glycolipid nature. The isolated strains are later employed in the MFCs for the degradation of the hydrocarbon and power production simultaneously which has shown a power density of 6.4 W/m3 with a 93% engine oil degradation rate. A biogenic Fe2O3 nanoparticle (NP) was synthesized using Bambusa arundinacea shoot extract for anode modification. It increased the power output by 37% and gave the power density of 10.2 W/m3. Thus, simultaneous hydrocarbon bioremediation from oil-contamination and energy recovery can be achieved effectively in MFC with modified anode.

Isolation and Screening of Biosurfactant-Producing Bacteria from Hydrocarbon-Contaminated Soils in Awka, Southeast, Nigeria

Background: Biosurfactants are a variety of groups of active compounds produced by various types of microorganisms. Bacterial surfactants are suitable for a range of applications in the oil industry, food, agriculture, pharmaceutical, cosmetics and bioremediation. Therefore, the search for sustainable alternatives to production of chemical biosurfactant is widely being encouraged.
 Aim: The present study aimed to isolate and screen bacterial species for biosurfactant production.
 Methodology: Two hundred soil samples collected from hydrocarbon contaminated soils in Awka, Nigeria, were cultured on casein starch agar. The isolates were screened for biosurfactant production stability and antimicrobial activity.
 Results: Primary screening on the 87 recovered isolates using drop collapse, oil spreading, haemolysis tests showed that 16 isolates (18.39%) were biosurfactant producers. Secondary screening resulted in 9 isolates with good emulsification index (E24) ranging from 42.18% to 74.07%. The culture supernatant of the isolates containing biosurfactants were stable at varying pH (2 – 12), temperature (4 - 121˚C) and salinity (2 – 20%). Most isolates have antimicrobial activity against Escherichia coli and Staphylococcus aureus. Based on oil spreading, emulsification index and antimicrobial activity, four of the isolates, ASP, AS1, DS4, DS8, were selected as most efficient in biosurfactant production. Phylogenetic analysis based on 16S rRNA genes classified ASP as Streptomyces sp, AS1 as Actinomyces sp, DS4 and DS 8 as species of Alcaligenes faecalis.
 Conclusion: All the species investigated were observed to be active biosurfactant producers. The stability of the biosurfactants, and their antimicrobial nature, make them suitable candidates for use in various industrial sectors.

Microbial Biosurfactant Screening: Diversity in Assessment Methods

Abstract Biosurfactants are a group of surface-active agents mainly produced by microorganisms and have a wide range of applications in industries as well as agriculture. Global usage of such biologically active compounds as detergents, bioremediation agents, cosmetic products is hugely dependent on their high production. New avenues of research have opened up due to this increased interest, most of which are focused on identifying specialized microorganisms capable of biosurfactant production. Screening methods for selection of biosurfactant producing bacteria are, therefore, of utmost importance in this endeavor. The aim of this review was to discuss various conventional and novel methods that can overcome the hurdles encountered in time effective, economical microbial biosurfactant screening. This review lists several important biosurfactant screening methods based on supernatant, biomass as well as culture media. New methods devised for biosurfactant screening in the last half decade such as surfactant dependent dye solubilization, metagenomic studies etc. are also explained in detail. A thorough grasp of both contemporary and anachronistic screening methodologies will not only lead to discoveries of novel native strains capable of biosurfactant production but also form the basis on which new screening methods can be devised.

Biodegradation of carbofuran by Pseudomonas aeruginosa S07: biosurfactant production, plant growth promotion, and metal tolerance.

Pesticides are an indispensable part of modern farming as it aids in controlling pests and hence increase crop yield. But, unmanaged use of pesticides is a growing concern for safety and conservation of the environment. In the present study, a novel biosurfactant-producing bacterium, Pseudomonas aeruginosa S07, was utilized to degrade carbofuran pesticide, and it was obtained at 150 mg/L concentration; 89.2% degradation was achieved on the 5th day of incubation in in vitro culture condition. GC-MS (gas chromatography and mass spectrometry) and LC-MS (liquid chromatography and mass spectrometry) analyses revealed the presence of several degradation intermediates such as hydroxycarbofurnan, ketocarbofuran, and hydroxybenzofuran, in the degradation process. The bacterium was found to exhibit tolerance towards several heavy metals: Cu, Co, Zn, Ni, and Cd, where maximum and least tolerance were obtained against Co and Ni, respectively. Additionally, the bacterium also possesses plant growth-promoting activity showing positive results in nitrogen fixation, phosphate solubilising, ammonia production, and potassium solubilizing assays. Thus, from the study, it can be assumed that the bacterium can be useful in the production of bioformulation for remediation and rejuvenation of pesticide-contaminated sites in the coming days.

Identification and Screening of Biosurfactant Producing Bacteria from Mechanic Workshops Soil in Gusau Metropolis, Nigeria

Biosurfactants are molecules that reduce interfacial tension. Their chemical composition can vary widely, but they have in common their amphiphilic or amphipatic nature and can thus be soluble in aqueous as well as in organic solvents. The study was carried out to identify and screen biosurfactant producing bacteria from mechanic workshops in Gusau metropolis. Eight (8) soil samples were collected at the depth of 0-7 and 8-15cm from selected mechanic workshops located at Gada Biyu, Taqama bye-pass, Birnin Ruwa and non-oil contaminated soil as control for analysis. The physicochemical parameters were analysed using standard procedures (blood heamolysis, drop collapse, oil displacement and emulsification index) methods were used to screen biosurfactant production by the isolates. Mineral salt medium supplemented with 1% Actual gasoline oil (AGO) as sole sources of carbon was used to isolate hydrocarbon degrading bacteria, while heterotrophic bacteria were isolated using nutrient Agar. The soil samples from the study area were characterised with smooth, grey to dark brown soil with an unpleasant smell as well as as well as high temperature and pH. The three mechanic workshops used for this study, shows relatively higher counts for Hydrocarbon Degrading Bacteria while higher heterotrophic bacterial count was obtained from the control site though there was no significant difference between individual mechanic workshop (p>0.05). The isolates are potential biosurfactant producers based on their performance especially blood haemolysis and emulsification index. The isolates identified belonged to the species of Bacillus, Pseudomonas, Acinetobacter, Micrococcus and Serratia.

Alternative stable microbiome state triggered by the introduction of functional microbes in oil reservoirs drives sustainable microbial enhanced oil recovery

Microbial enhanced oil recovery (MEOR) is a promising substitute for other enhanced oil recovery methods in terms of sustainable development. However, the response mechanism of the microbial community to the introduction of functional microbes remains unclear, which limits MEOR strategic planning to achieve a long-term effect. In this study, we reveal the existence of alternative stable states in an oil reservoir for the first time and examine the correlation between the microbiota status and the oil production increment. There existed a basal state A and alternative state B in the reservoir microbial community, and this resulted in a differential microbial oil displacement effect. The oil production increased by up to 50% in basal state A, because Halomonas dominated most niches and restrained other functional microbes. The introduction of biosurfactant-producing bacteria triggered the microbiota status to shift to the alternative state B associated with higher oil recovery. In state B, the high microbial diversity and positive interaction among Dietzia, Bacillus and other species significantly activated the effectiveness of the microbial oil displacing function. Due to the hysteresis of the microbial community, it required frequent and intensive introduction of functional microbes to improve the microbiota in the reservoir and sustainably promote oil recovery. Overall, this study provides new insights into the response mechanism of the microbial community to the introduction of functional microbes in an oil reservoir. This study also provides guidance for effective management of a MEOR strategy to achieve sustainably enhanced oil production.

Production of surfactin from novel Bacillus spp. isolated from soil and its antifungal properties

Aim: This research aimed to screen the biosurfactant-producing bacteria from soil, especially for the betterment of the environment in terms of bioremediation and biodegradation of lipids and hydrocarbons. Methodology: Bacillus spp. isolated from the soil was cultured and inoculated into different mineral media such as Glucose, Sawdust, and Bagasse mineral media. The surfactin was extracted and the activity was studied using oil emulsification test, oil spreading assay, and drop collapse assay. Bacillus spp. that provided better results were sequenced and submitted to NCBI. The surfactin of the specific bacteria was characterized using TLC, UV-vis spectra, and FTIR analysis. Finally, the antifungal activity assay was performed against Aspergillus flavus, Rhizopus spp., and Aspergillus niger. Results: Bacillus species subjected to gene sequencing was identified as Bacillus mycoids strain ARJCBNR (On464184). UV-vis spectra and FTIR analyses revealed various functional groups such as 3356.14 cm-1 (N-H stretch), 1635.64 cm-1 (C=O amide), and 1211 cm-1 (C-O stretch) representing the surfactin compound between 4000 and 500 cm-1. Upon antifungal activity, sawdust-extracted surfactin had a higher zone of inhibition against all the tested fungi. Interpretation: This study revealed that Bacillus spp. can utilize agro-industrial waste as substrate to produce surfactin. Also, the surfactin extracted from sawdust mineral media showed higher antifungal activity. Key words: Bacillus spp., Biosurfactant, Mineral media, Soil, Surfactin

Isolation and Characterization of Biosurfactant-producing Bacteria from Ternary Effluent within Maiduguri Metropolitan Council

Almost all surfactants currently in use are chemically derived from petroleum. However, the diversity of biosurfactants, environment friendly characteristics, the possibility of their production through fermentation and their potential applications in areas such as environmental protection, surface crude oil recovery, health care and food processing industries, has made its interest steadily increasing in recent years. This research is targeted towards the isolation of indigenous biosurfactant producing bacteria from the local tanneries in Maiduguri. Physico – chemical parameters such as temperature and pH of all samples were tested at the site of collection, while others such as Biochemical Oxygen Demand (BOD), Desolved Oxygen (DO) and Electrical Conductivity (EC) were tested ex – situ. Simple and selective microbiological media were used for the isolation. A total of ten (10) different bacterial isolates were obtained from the eighteen (18) samples tested. Identification of the isolates was achieved through morphological and Biochemical analysis. The isolates obtained included Providencia rettgeri, Salmonella enterica, Enterobacter cancerogenus, Leminorella richardii, Bacillus licheniformis, B. niacini, Paenibacillus residui, Proteus mirabilis, Lysinibacillus massiliensis and L. fusiformis. Of the ten (10) isolates obtained, only seven (7) were found positive for biosurfactant production. They incuded P. rettgeri, E. cancerogenus, L. richardii, B. niacini, P. residui, L. massiliensis and L. fusiformis, of which L. fusiformis showed the highest emulsification activity of 25% at 4cm emulsion height. The results suggest that the Majema tannery effluents harbour biosurfactant - producing bacteria. Thus, tannery effluents can be possibly remediated using the biosurfactants and bacteria producing the biosurfactants.

Bioprospecting of biosurfactant-producing bacteria for hydrocarbon bioremediation: Optimization and characterization

Bioprospecting of biosurfactant-producing bacteria for hydrocarbon bioremediation: Optimization and characterization

Genome analysis of biosurfactant producing bacterium, Bacillus tequilensis.

Bioremediation is crucial for recuperating polluted water and soil. By expanding the surface area of substrates, biosurfactants play a vital role in bioremediation. Biosurfactant-producing microbes release certain biosurfactant compounds, which are promoted for oil spill remediation. In the present investigation, a biosurfactant-producing bacterium Bacillus tequilensis was isolated from Chilika Lake, Odisha, India (latitude and longitude: 19.8450 N 85.4788 E). Whole-Genome Sequencing (WGS) of Bacillus tequilensis was carried out using Illumina NextSeq 500. The size of the whole genome of Bacillus tequilensis was 4.47 MB consisting of 4,478,749 base pairs forming a circular chromosome with 528 scaffolds, 4492 protein-encoding genes (ORFs), 81 tRNA genes, and 114 ribosomal RNA transcription units. The total raw reads were 4209415, and the processed reads were 4058238 with 4492 genes. The whole genome obtained from the present investigation was used for genome annotation, variant calling, variant annotation, and comparative genome analysis with other existing Bacillus species. In this study, a pathway was constructed which describes the biosurfactant metabolism of Bacillus tequilensis. The study identified that genes such as SrfAD, SrfAC, SrfAA and SrfAB are involved in biosurfactant synthesis. The sequence of the genes SrfAD, SrfAC, SrfAA, SrfAB was deposited in GenBank database with accession MUG02427.1, MUG02428.1, MUG02429.1, MUG03515.1 respectively. The whole genome sequence was submitted to GenBank with an accession RMVO00000000 and the raw fastq reads were submitted to SRA, NCBI repository with an accession: SRX5023292.

Biosurfactant-Producing Bacteria and Microbial Analysis in Mae Soon Reservoir, Fang Oil Field, Chiang Mai, Thailand

Microbial Enhanced Oil Recovery (MEOR) is an effective alternative method for oil recovery in reservoirs using microorganisms or their secondary metabolites. This research aimed to evaluate the indigenous bacteria from Mae Soon reservoir by culture-dependent and culture-independent methods and to investigate the potential of biosurfactant-producing bacteria using a drop-collapsed assay. Indigenous bacteria were isolated from the oil sands of the reserved core of Mae Soon reservoir using fi ve different media (nutrient, Luria-Bertani, mineral salt, tryptic soy, and peptone yeast extract). Fifty-four facultative anaerobic bacterial isolates were obtained. Seven isolates showed their potential as biosurfactant producers in the drop-collapse assay. Based on 16S rRNA gene analysis, six of the biosurfactant-producing bacterial isolates belonged to the species Bacillus licheniformis and one belonged to the species B. subtilis. The biosurfactant producers and microbial community in the oil sands were determined using Denaturing Gradient Gel Electrophoresis (DGGE). Interestingly, DGGE bands corresponding to bacteria belonging to the genus Geobacillus sp. were detected. Overall, the results obtained from this work showed that indigenous bacteria in Mae Soon reservoir oil well were prospective for use in MEOR.

Study on Optimization, Degreasing and Destaining Potentials of Glycophospholipid Biosurfactant Produced by Bacillus Anthracis S62A

Oil-polluted soil is one of the major sources of biosurfactant producing bacteria. This study was to study the optimization, degreasing and de-staining potentials of glycophospholipid biosurfactant produced by B. anthracis strain S62A isolated from spent engine oil-polluted soil. Five (5) bacterial isolates associated with spent engine oil – polluted soil was primarily screened for biosurfactant production using emulsification index test, oil displacement test, and surface tension test. The bacterial isolate with the highest screening test results was selected, characterized and examined for its biosurfactant production optimization, degreasing and de-staining potential on different oil-stained fabric materials. The results showed that the parameters required for the maximum biosurfactant yield were 20 g of slaughter house waste, 10 g of rice bran, 1% of sodium chloride, 9.0 pH, 4 °C temperature, 10% of the test bacterial inoculum and 5 days incubation period. The biochemical profile revealed that the extracted biosurfactant was identified as glycophospholipid. The maximum cleaning and degreasing efficiency of the biosurfactant obtained from B. anthracis strain S62A was observed to possess 78, 72 and 64 % oil removal efficiency from stained polyester, cotton and chiffon fabric materials, respectively at 10 mg/mL critical micelles concentration (CMC). Statistically, significant differences (P < 0.05) were detected among the means of all surfactant concentration treatments in comparison to their controls using two-way ANOVA followed by Dunnett comparison test. Therefore, this study suggests that the glycophospholipid biosurfactant from B. anthracis strain S62A could be exploited in laundry industries for the formulation of detergents as well as in textile dye biotreatment.

Isolation and Characterization of Biosurfactant Producing Pseudomonas aeruginosa YLA03 and its Diesel Degradation Potentials

This work was aimed at isolating and characterising biosurfactant producing bacteria strain from diesel oil contamination sites. The potential of the strain  to degrade diesel oil n-alkanes was further studied. Soil samples were collected from diesel rich areas, and identified strains were grown on  minimal media that contained diesel oil as only carbon source. Enrichment culture technique was used to identify bacteria. Seventeen bacteria strains  were identified based on their capacity to use diesel oil as carbon source. Other qualitative screening methods were employed to determine the potential  to produce biosurfactants. Isolate A03 was the only candidate that shows positive signs for drop collapse, foaming, haemolytic, oil  displacement and emulsification tests. The effect of various culture parameters (incubation time, concentration of diesel, nitrogen source, pH and  temperature) on biodegradation of diesel was evaluated. Optimum pH was 8.0 at 35° C, while the incubation time at maximum bacteria growth was five  (5) days. The favourable diesel oil concentration was 7.5% for the isolate. The isolate has shown degradative ability towards dodecane, Tridecane,  tetradecane but was unable to degrade 2, 6, 10-trimethyl- dodecane. It degraded between 10.09% - 45.39% of individual diesel alkanes. The strain has  exhibited potential for degrading diesel alkanes and was identified as pseudomonas aeruginosa strain A3 (Accession Number: MZ027605) using the 16S  rRNA. Sequencing. 

Isolation and Characterization of Viscosity-Reducing and Biosurfactant-Producing Bacteria in Low-Permeability Reservoir

Microbialenhanced oil recovery has gained more attention in recent years due to its low cost and eco-friendliness. However, studies on the application of this technique in the low-permeability reservoirs are few. In this study, eight strains from the Ordos Basin low-permeability reservoir that produce biosurfactant and reduce viscosity were identified. Strains could produce biosurfactants (lipopeptide and glycolipids) to emulsify the oil and had good tolerance on temperature (25°C-50°C), salinity (1 g/L-50g/L), and pH (5-10). After the actions of A-3, SC4534(2), SC4561, and JSC4535, the content of long-chain n-alkanes were decreased by 51.2%, 28.3%, 35.2%, and 28.9%, respectively. The naphthalene in aromatic hydrocarbons was also effectively degraded by the strains that were screened, and the degradation rate was higher than 84%. Additionally, all strains were able to reduce oil viscosity, which was reduced by 27-51% (in seven days). 16S rRNA gene sequencing analysis indicated that seven strains belong to the genus Bacillus and one belongs to the genus Rhodospirillaceae. The results revealed that the existence of high-efficiency strains that can significantly improve the properties of crude oil in low-permeability oil fields though biodegradation and use of biosurfactants, which is of great significance for the application of MEOR in low-permeability oil fields.

The application of biosurfactant-producing bacteria immobilized in PVA/SA/bentonite bio-composite for hydrocarbon-contaminated soil bioremediation.

Oil spills that contaminate the environment can harm the surrounding ecosystem. The oil contains petroleum hydrocarbon which is toxic to the environment hence it needs to be removed. The use of bacteria as remediation media was modified by immobilizing into a matrix hence the bacteria can survive in harsh conditions. In this research, the ability of biosurfactant-producing bacteria (Pseudomonas aeruginosa, Bacillus subtilis, and Ralstonia pickettii) immobilized in the PVA/SA/bentonite matrix was tested in remediation on oil-contaminated soil. The immobilized beads filled with bacteria were added to the original soil sample, as well as washed soil. The beads were characterized by using FTIR and SEM. Based on FTIR analysis, the PVA/SA/bentonite@bacteria beads had similar functional groups compared to each other. SEM analysis showed that the beads had non-smooth structure, while the bacteria were spread outside and agglomerated. Furthermore, GC-MS analysis results showed that immobilized B. subtilis and R. pickettii completely degraded tetratriacontane and heneicosane, respectively. Meanwhile, after soil washing pre-treatment, immobilized bacteria could completely degrade octadecane (P. aeruginosa and R. pickettii) and tetratriacontane (P. aeruginosa and B. subtilis). Based on those results, immobilized bacteria could degrade oil compounds. The degradation result was influenced by the enzymes produced, the ability of the bacteria, the suitability of the test media, and the matrix used. Therefore, this study can be a reference for further soil remediation using eco-friendly methods.