Characterization and Application of Biosurfactant Produced by Bacillus licheniformis R2

Application of biosurfactants in enhanced oil recovery ex-situ: a review

With a growing focus on environmentally friendly solutions, biosurfactants derived from plants or microorganisms have gained attention for Enhanced Oil Recovery (EOR) applications. Biosurfactants offer several advantages over existing options, including biodegradability, low toxicity, availability of raw materials, resistance to harsh reservoir conditions, and improved water/oil interfacial tension reduction. Different organisms, such as bacteria, fungi, and plants, can produce these natural surfactants. Bacillus sp. and Pseudomonas sp. bacteria are extensively studied for their ability to produce biosurfactants using low-cost carbon and nitrogen sources, exhibiting excellent surface activity and low critical micellar concentration (CMC). Fungi, though less commonly used, can also produce biosurfactants, albeit with lower interfacial activity. Plant-derived natural surfactants find wide application in laboratory tests for EOR, despite having higher CMC. This review not only summarizes the current knowledge on biosurfactants but also offers a novel comparative analysis of those produced by bacteria, fungi, and plants, examining their CMC, surface tension, and interfacial tension properties. Additionally, it quantifies the number of publications on the use of biosurfactants for Microbial Enhanced Oil Recovery ex-situ (MEOR ex-situ) over the past 30 years and compares these with biosurfactants derived from plant sources. Our study is unique in its comparative approach and the quantification of literature on MEOR ex-situ. The findings reveal that biosurfactants produced by bacteria generally exhibit superior surface activity, even at lower concentrations, compared to those produced by plants or fungi. This new comparative perspective and thorough literature analysis highlight the distinctive contributions of this study. Overall, the use of biosurfactants for EOR represents a promising approach to cleaner energy production, with the potential to reduce environmental impact while improving oil recovery.

Exploring the potential of biosurfactants produced by fungi found in soil contaminated with petrochemical wastes

Biosurfactants are a diverse group of compounds derived from microorganisms, possessing various structures and applications. The current study was seeking to isolate and identify a new biosurfactant-producing fungus from soil contaminated with petrochemical waste. The bioprocess conditions were optimized to maximize biosurfactant production for Aspergillus carneus OQ152507 using a glucose peptone culture medium with a pH of 7.0 and a temperature of 35 °C. The carbon source was glucose (3%), and ammonium sulfate (0.25%) was utilized as the nitrogen source. For Aspergillus niger OQ195934, the optimized conditions involved a starch nitrate culture medium with a pH of 7.0 and a temperature of 30 °C. The carbon source used was sucrose (3.5%), and ammonium sulfate (0.25%) served as the nitrogen source. The phenol-H2SO4 and phosphate tests showed that the biosurfactants that were extracted did contain glycolipid and/or phospholipid molecules. They showed considerable antimicrobial activity against certain microbes. The obtained biosurfactants increased the solubility of tested polyaromatic hydrocarbons, including fluoranthene, pyrene, anthracene, and fluorine, and successfully removed the lubricating oil from contaminated soil and aqueous media surface tension reduction. Based on the obtained results, A. carneus and A. niger biosurfactants could be potential candidates for environmental oil remediation processes.

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.

Lichenysin-like Polypeptide Production by Bacillus licheniformis B3-15 and Its Antiadhesive and Antibiofilm Properties

We report the ability of the crude biosurfactant (BS B3-15), produced by the marine, thermotolerant Bacillus licheniformis B3-15, to hinder the adhesion and biofilm formation of Pseudomonas aeruginosa ATCC 27853 and Staphylococcus aureus ATCC 29213 to polystyrene and human cells. First, we attempted to increase the BS yield, optimizing the culture conditions, and evaluated the surface-active properties of cell-free supernatants. Under phosphate deprivation (0.06 mM) and 5% saccharose, the yield of BS (1.5 g/L) increased by 37%, which could be explained by the earlier (12 h) increase in lchAA expression compared to the non-optimized condition (48 h). Without exerting any anti-bacterial activity, BS (300 µg/mL) prevented the adhesion of P. aeruginosa and S. aureus to polystyrene (47% and 36%, respectively) and disrupted the preformed biofilms, being more efficient against S. aureus (47%) than P. aeruginosa (26%). When added to human cells, the BS reduced the adhesion of P. aeruginosa and S. aureus (10× and 100,000× CFU/mL, respectively) without altering the epithelial cells' viability. As it is not cytotoxic, BS B3-15 could be useful to prevent or remove bacterial biofilms in several medical and non-medical applications.

Bacillus licheniformis: A Producer of Antimicrobial Substances, including Antimycobacterials, Which Are Feasible for Medical Applications

Bacillus licheniformis produces several classes of antimicrobial substances, including bacteriocins, which are peptides or proteins with different structural composition and molecular mass: ribosomally synthesized by bacteria (1.4-20 kDa), non-ribosomally synthesized peptides and cyclic lipopeptides (0.8-42 kDa) and exopolysaccharides (>1000 kDa). Different bacteriocins act against Gram-positive or Gram-negative bacteria, fungal pathogens and amoeba cells. The main mechanisms of bacteriocin lytic activity include interaction of peptides with membranes of target cells resulting in structural alterations, pore-forming, and inhibition of cell wall biosynthesis. DNase and RNase activity for some bacteriocines are also postulated. Non-ribosomal peptides are synthesized by special non-ribosomal multimodular peptide synthetases and contain unnatural amino acids or fatty acids. Their harmful effect is due to their ability to form pores in biological membranes, destabilize lipid packaging, and disrupt the peptidoglycan layer. Lipopeptides, as biosurfactants, are able to destroy bacterial biofilms. Secreted polysaccharides are high molecular weight compounds, composed of repeated units of sugar moieties attached to a carrier lipid. Their antagonistic action was revealed in relation to bacteria, viruses, and fungi. Exopolysaccharides also inhibit the formation of biofilms by pathogenic bacteria and prevent their colonization on various surfaces. However, mechanism of the harmful effect for many secreted antibacterial substances remains unknown. The antimicrobial activity for most substances has been studied in vitro only, but some substances have been characterized in vivo and they have found practical applications in medicine and veterinary. The cyclic lipopeptides that have surfactant properties are used in some industries. In this review, special attention is paid to the antimycobacterials produced by B. licheniformis as a possible approach to combat multidrug-resistant and latent tuberculosis. In particular, licheniformins and bacitracins have shown strong antimycobacterial activity. However, the medical application of some antibacterials with promising in vitro antimycobacterial activity has been limited by their toxicity to animals and humans. As such, similar to the enhancement in the antimycobacterial activity of natural bacteriocins achieved using genetic engineering, the reduction in toxicity using the same approach appears feasible. The unique capability of B. licheniformis to synthesize and produce a range of different antibacterial compounds means that this organism can act as a natural universal vehicle for antibiotic substances in the form of probiotic cultures and strains to combat various types of pathogens, including mycobacteria.

Prediction of surfactin fermentation with Bacillus subtilis DSM10 by response surface methodology optimized artificial neural network

Biosurfactants produced by Bacillus species are an emerging group of surface-active molecules. They have excellent surface tension reducer and high emulsifier properties. Generally, the biosurfactant fermentation leads to a low product concentration. Therefore, our goal was to investigate Bacillus subtilis DSM10 production and improve the biosurfactant content in the broth by media optimization via response surface methodology. The optimal combinations of the investigated factors were determined as the following: pH = 9, glucose = 20 g/L, and NH₄ NO₃  = 2 g/L. Under the optimized conditions, the formed surfactin strain reduced surface tension in the broth by 48% (from 72 to 37 mN/m) and the isolated product by 63% (from 72 to 27 mN/m). An artificial neural network was built based on the results of response surface methodology to predict the product quality and the harvesting time of broth. Thus, finally, the model can predict the final cell and product amount, and even their time course, with around 90% reliability.

Antibacterial activity of Bacillus licheniformis B6 against viability and biofilm formation of foodborne pathogens of health importance

We studied a strain of Bacillus isolated from an artisanal tannery in Salta, Argentina. It was identified as Bacillus licheniformis B6 by 16 S phylogenetic analysis and MALDI TOF (GenBank accession code No. KP776730). The synthesis of lipopeptides by B6 and their antibacterial activity against clinical pathogenic strains was analyzed both in the cell-free supernatant (CFS) and in the crude fraction of lipopeptides (LF). Overall, the CFS did not significantly reduce the viability of the studied strains (Staphylococcus aureus 269 and ATCC 43,300, Escherichia coli 4591 and 25,922, Klebsiella sp. 1087 and 1101). However, LF at 9 mg/mL reduced the viability of those pathogenic strains by 2 and 3 log orders compared to those of the control. When the effects of LF and ampicillin were compared, they showed different sensitivity against pathogenic strains. For example, E. coli 4591 was the strain most resistant to ampicillin, requiring 250 mg/mL of antibiotic to achieve the same inhibitory effect as 9 mg/mL of B6 LF. SEM observations of the effect of LF on biofilm formation by E. coli 4591 and Klebsiella sp. 1087 clearly showed that biofilm structures were destabilized, these strains turning into weak biofilm formers. Signals in the CFS and LF corresponding to kurstakin and iturin were identified by MALDI TOF. Interestingly, surfactin was detected, rather than lichenysin, the expected lipopeptide in B. licheniformis species. Signals of bacitracin and fengycins were also found, the latter with a higher number of homologues and relative intensity in the LF than the other lipopeptides. These results show that the lipopeptides synthesized by B. licheniformis B6 have both potential antibacterial and anti-biofilm activity against pathogenic bacteria of health importance.

Bacillus licheniformis: The unexplored alternative for the anaerobic production of lipopeptide biosurfactants?

Microbial biosurfactants have attracted the attention of researchers and companies for the last decades, as they are considered promising candidates to replace chemical surfactants in numerous applications. Although in the last years, considerable advances were performed regarding strain engineering and the use of low-cost substrates in order to reduce their production costs, one of the main bottlenecks is their production at industrial scale. Conventional aerobic biosurfactant production processes result in excessive foaming, due to the use of high agitation and aeration rates necessary to increase dissolved oxygen concentration to allow microbial growth and biosurfactant production. Different approaches have been studied to overcome this problem, although with limited success. A not widely explored alternative is the development of foam-free processes through the anaerobic growth of biosurfactant-producing microorganisms. Surfactin, produced by Bacillus subtilis, is the most widely studied lipopeptide biosurfactant, and the most powerful biosurfactant known so far. Bacillus licheniformis strains produce lichenysin, a lipopeptide biosurfactant which structure is similar to surfactin. However, despite its extraordinary surface-active properties and potential applications, lichenysin has been scarcely studied. According to previous studies, B. licheniformis is better adapted to anaerobic growth than B. subtilis, and could be a good alternative for the anaerobic production of lipopeptide biosurfactants. In this review, the potential and limitations of surfactin and lichenysin production under anaerobic conditions will be analyzed, and the possibility of implementing foam-free processes for lichenysin production, in order to expand the market and applications of biosurfactants in different fields, will be discussed.

Minimizing hazard impacts of soil salinity and water stress on wheat plants by soil application of vermicompost and biochar

Soil water and nutrient status are two of the most important factors for plant development and crop yield. Vermicompost and biochar are supposed to amend soil attributes and increase the productivity. However, little is known about their mixture application on soil quality and nutrient uptake under natural conditions. The aim of this investigation was to understand the impact of soil amendments (control, vermicompost, biochar, and vermicompost + biochar) on yield, soil quality, physiological and biochemical attributes, as well as nutrient uptake of wheat plants grown at different irrigation water treatments (50%, 75%, and 100% of field capacity [FC]) in saline sodic soil. Vermicompost improved wheat growth and yield. Biochar-treated plants had higher growth performance and yield than control plants in all traits and than vermicompost in some cases, thus confirming its potential for enhancing soil quality and increasing nutrient uptake, which stimulates soil chemical properties. When vermicompost was added in combination with biochar, further enhancement in the growth and yield was recorded, highlighting the beneficial effect of vermicompost on plant yield. Vermicompost-biochar mixture application followed by biochar as a singular application caused significant improvements in relative water content, chlorophyll content, stomatal conductance, cytotoxicity, leaf K⁺ content with respect to nutrient uptake (N, P, and K), while reducing oxidative stress (i.e., activities of catalase [CAT] and ascorbate peroxidase [APX], and expression levels of CAT, APX, and Mn-SOD genes), leaf Na⁺ content, and proline content. This resulted in increases in yield-related traits and productivity owing to the enhancement in soil chemical characteristics and soil moisture content. Grain yield and nutrient uptake attained the highest values at 75% FC in wheat plants treated by the combination of vermicompost and biochar. In summary, this investigation revealed that the synergistic effect of vermicompost and biochar can not only enhance crop production but also eliminates the detrimental effects of soil salinity and water stress.

A review on biosurfactants: properties, applications and current developments

Microbial surfactants are a large number of amphipathic biomolecules with a myriad of biomolecule constituents from various microbial sources that have been studied for their surface tension reduction activities. With unique properties, their applications have been increased in different areas including environment, medicine, healthcare, agriculture and industries. The present review aims to study the biochemistry and biosynthesis of biosurfactants exhibiting varying biomolecular structures which are produced by different microbial sources. It also provides details on roles played by biosurfactants in nature as well as their potential applications in various sectors. Basic biomolecule content of all the biosurfactants studied showed presence of carbohydrates, aminoacids, lipids and fattyacids. The data presented here would help in designing, synthesis and application of tailor-made novel biosurfactants. This would pave a way for perspectives of research on biosurfactants to overcome the existing bottlenecks in this field.

Biotechnological applications of Bacillus licheniformis

Bacillus licheniformis is a Gram positive spore-forming bacterial species of high biotechnological interest with numerous present and potential uses, including the production of bioactive compounds that are applied in a wide range of fields, such as aquaculture, agriculture, food, biomedicine, and pharmaceutical industries. Its use as an expression vector for the production of enzymes and other bioproducts is also gaining interest due to the availability of novel genetic manipulation tools. Furthermore, besides its widespread use as a probiotic, other biotechnological applications of B. licheniformis strains include: bioflocculation, biomineralization, biofuel production, bioremediation, and anti-biofilm activity. Although authorities have approved the use of B. licheniformis as a feed additive worldwide due to the absence of toxigenic potential, some probiotics containing this bacterium are considered unsafe due to the possible transference of antibiotic resistance genes. The wide variability in biological activities and genetic characteristics of this species makes it necessary to establish an exact protocol for describing the novel strains, in order to evaluate its biotechnological potential.

Biosurfactants and Their Applications in the Oil and Gas Industry: Current State of Knowledge and Future Perspectives

Surfactants are a group of amphiphilic chemical compounds (i.e., having both hydrophobic and hydrophilic domains) that form an indispensable component in almost every sector of modern industry. Their significance is evidenced from the enormous volumes that are used and wide diversity of applications they are used in, ranging from food and beverage, agriculture, public health, healthcare/medicine, textiles, and bioremediation. A major drive in recent decades has been toward the discovery of surfactants from biological/natural sources-namely bio-surfactants-as most surfactants that are used today for industrial applications are synthetically-manufactured via organo-chemical synthesis using petrochemicals as precursors. This is problematic, not only because they are derived from non-renewable resources, but also because of their environmental incompatibility and potential toxicological effects to humans and other organisms. This is timely as one of today's key challenges is to reduce our reliance on fossil fuels (oil, coal, gas) and to move toward using renewable and sustainable sources. Considering the enormous genetic diversity that microorganisms possess, they offer considerable promise in producing novel types of biosurfactants for replacing those that are produced from organo-chemical synthesis, and the marine environment offers enormous potential in this respect. In this review, we begin with an overview of the different types of microbial-produced biosurfactants and their applications. The remainder of this review discusses the current state of knowledge and trends in the usage of biosurfactants by the Oil and Gas industry for enhancing oil recovery from exhausted oil fields and as dispersants for combatting oil spills.

Optimization of biosurfactant production from Pseudomonas sp. CQ2 and its application for remediation of heavy metal contaminated soil

The present study was conducted to enhance the biosurfactant production yield of Pseudomonas sp. CQ2 isolated from the Chongqing oilfield (China). Besides, the capability of biosurfactant and underlying mechanism for remediation of heavy metal contaminated soil was also investigated. Our results suggested that maximum biosurfactant production (40.7 g/L) was attained at 35 °C by using soybean oil and ammonium nitrate as carbon and nitrogen sources with pH 7, rotational speed of 175 rpm and inoculation ratio of 3%). The removal efficiencies of 78.7, 65.7 and 56.9% for Cd, Cu and Pb respectively were achieved at optimized bioleaching conditions (pH: 11, soil/solution ratio: 30:1 and non-sterilized soil), comparative tests between common chemical surfactants (SDS, Tween-80) and biosurfactants demonstrated the larger removal capacity of biosurfactants. Through SEM-EDX, it was found that the granular material disappeared, the content of Cd, Cu and Pb decreased significantly, and the soil surface became smooth with hole formation after soil washing following bioleaching. ATR-FTIR results showed that the carboxyl functional groups in biosurfactants could chelate heavy metals. These results indicated that biosurfactants from Pseudomonas sp. CQ2 could effectively eliminate Cd, Cu, and Pb from soil.

Development and Genetic Engineering of Hyper-Producing Microbial Strains for Improved Synthesis of Biosurfactants

Current research energies are fixated on the synthesis of environmentally friendly and non-hazardous products, which include finding and recognizing biosurfactants that can substitute synthetic surfactants. Microbial biosurfactants are surface-active compounds synthesized intracellularly or extracellularly. To use biosurfactants in various industries, it is essential to understand scientific engagements that demonstrate its potentials as real advancement in the 21st century. Other than applying a substantial effect on the world economic market, engineered hyper-producing microbial strains in combination with optimized cultivation parameters have made it probable for many industrial companies to receive the profits of 'green' biosurfactant innovation. There needs to be an emphasis on the worldwide state of biosurfactant synthesis, expression of biosurfactant genes in expressive host systems, the recent developments, and prospects in this line of research. Thus, molecular dynamics with respect to genetic engineering of biosynthetic genes are proposed as new biotechnological tools for development, improved synthesis, and applications of biosurfactants. For example, mutant and hyper-producing recombinants have been designed efficaciously to advance the nature, quantity, and quality of biosurfactants. The fastidious and deliberate investigation will prompt a comprehension of the molecular dynamics and phenomena in new microorganisms. Throughout the decade, valuable data on the molecular genetics of biosurfactant have been produced, and this solid foundation would encourage application-oriented yields of the biosurfactant production industry and expand its utilization in diverse fields. Therefore, the conversations among different interdisciplinary experts from various scientific interests such as microbiology, biochemistry, molecular biology, and genetics are indispensable and significant to accomplish these objectives.

Investigation of Bacillus licheniformis in the biodegradation of Iranian heavy crude oil: A two-stage sequential approach containing factor-screening and optimization

Oil pollution is a serious international concern due to its harmful effect on human health and the environment. This study aims to investigate the effective factors on the biodegradation of Iranian heavy crude oil by Bacillus licheniformis. For this purpose, oil removal from the artificial seawater was studied by response surface methodology (RSM). After the screening experiments, pH (4-10), NaCl concentration (0-10 g/L), and oil concentration (500-4500 ppm) were selected as influential factors. Moreover, to evaluate the bacterial capability in bioremediation of an actual polluted site, crude oil spill with a salinity of 35 g/L was experimentally simulated. The proposed model in this study clearly shows that both selected individual factors and their interactions are significantly effective on the crude oil biodegradation capacity. The results showed that Bacillus licheniformis was able to degrade crude oil at different concentrations of oil, especially at low concentrations, which are challenging in actual polluted sites. 15%-66% removal was achieved for 500-4500 ppm of crude oil after 14 days. Furthermore, according to the obtained results, this bacterium can tolerate the salinity up to 3.5%. At this salinity level, crude oil removal was 23.43 and 25.64% in neutral and alkaline conditions, respectively. Process factors were optimized, and 54.8% of crude oil was removed at optimum conditions i.e., 3500 ppm crude oil concentration, 2.5 g/L of NaCl and pH equal to 8.5. Finally, it can be concluded that the selected bacterium of this study can be more effective in harsh environments such as hypersaline and alkaline conditions.

In Vitro and Ex Vivo Antibiofilm Activity of a Lipopeptide Biosurfactant Produced by the Entomopathogenic Beauveria bassiana Strain against Microsporum canis

Microsporum canis is one of the most important dermatophyte causing tinea corporis and tinea capitis and its biofilm-form has a poor therapeutic response. The biosurfactant production by entomopathogenic fungi (EPF) has not been reported yet. The study aimed to investigate the potential usage of the EPF biosurfactant in the eradication of an ex vivo biofilm of Microsporum canis (M. canis) for the first time. An entomopathogenic fungus was isolated from the fungal-infected Vespa orientalis wasp and identified as Beauveria bassiana (MN173375). Chemical characterization revealed the lipopeptide nature of the B. bassiana biosurfactant (BBLP). Efficient antifungal and antibiofilm activities of BBLP against M. canis in vitro were detected. An ex vivo hair model was used to investigate the efficiency of BBLP against M. canis biofilm, in a scenario close to the in vivo conditions. M. canis ex vivo biofilm eradication was confirmed in stereo, scanning electron, and fluorescent images. Also, the ex vivo biofilm was less susceptible to BBLP treatment compared to its in vitro counterpart. In conclusion, BBLP showed significant eradication to the M. canis ex vivo biofilm and open horizons to use bio-resource derived from EPF in controlling microbial biofilm and holding great promise for combating recalcitrant dermatophytosis.

Production and Application of Biosurfactant Produced by Bacillus Licheniformis Ali5 in Enhanced Oil Recovery and Motor Oil Removal from Contaminated Sand

The present study describes the production of biosurfactant from isolate B. licheniformis Ali5. Seven different, previously-reported minimal media were screened for biosurfactant production, and two selected media were further optimized for carbon source. Further, various fermentation conditions such as (pH 2–12, temperature 20–50 °C, agitation speed 100–300 rpm, NaCl (0–30 g·L⁻¹) were investigated. The partially purified biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) and found a lipopeptide mixture, similar to lichenysin-A. Biosurfactant reduced surface tension from 72.0 to 26.21 ± 0.3 and interfacial tension by 0.26 ± 0.1 mN·m⁻¹ respectively, biosurfactant yield under optimized conditions was 1 g·L⁻¹, with critical micelle concentration (CMC) of 21 mg·L⁻¹ with high emulsification activity of (E24) 66.4 ± 1.4% against crude oil. Biosurfactant was found to be stable over extreme conditions. It also altered the wettability of hydrophobic surface by changing the contact angle from 49.76° to 16.97°. Biosurfactant efficiently removed (70-79%) motor oil from sand, with an efficiency of more than 2 fold as compared without biosurfactant (36–38%). It gave 32% additional oil recovery over residual oil saturation upon application to a sand-packed column. These results are indicative of potential application of biosurfactant in wettability alteration and ex-situ microbial enhanced oil recovery.

Bacterial polyextremotolerant bioemulsifiers from arid soils improve water retention capacity and humidity uptake in sandy soil

Background

Water stress is a critical issue for plant growth in arid sandy soils. Here, we aimed to select bacteria producing polyextremotolerant surface-active compounds capable of improving water retention and humidity uptake in sandy soils.

Results

From Tunisian desert and saline systems, we selected eleven isolates able to highly emulsify different organic solvents. The bioemulsifying activities were stable with 30% NaCl, at 4 and 120 °C and in a pH range 4–12. Applications to a sandy soil of the partially purified surface-active compounds improved soil water retention up to 314.3% compared to untreated soil. Similarly, after 36 h of incubation, the humidity uptake rate of treated sandy soil was up to 607.7% higher than untreated controls.

Conclusions

Overall, results revealed that polyextremotolerant bioemulsifiers of bacteria from arid and desert soils represent potential sources to develop new natural soil-wetting agents for improving water retention in arid soils.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0934-7) contains supplementary material, which is available to authorized users.

First report of the production of a potent biosurfactant with α,β-trehalose by Fusarium fujikuroi under optimized conditions of submerged fermentation

Biosurfactants have many advantages over synthetic surfactants but have higher production costs. Identifying microorganisms with high production capacities for these molecules and optimizing their growth conditions can reduce cost. The present work aimed to isolate and identify a fungus with high biosurfactant production capacity, optimize its growth conditions in a low cost culture medium, and characterize the chemical structure of the biosurfactant molecule. The fungal strain UFSM-BAS-01 was isolated from soil contaminated with hydrocarbons and identified as Fusarium fujikuroi. To optimize biosurfactant production, a Plackett–Burman design and a central composite rotational design were used. The variables evaluated were pH, incubation period, temperature, agitation and amount of inoculum in a liquid medium containing glucose. The partial structure of the biosurfactant molecule was identified by nuclear magnetic resonance spectrometry. F. fujikuroi reduced surface tension from 72 to 20 mN m⁻¹ under the optimized conditions of pH 5.0, 37 °C and 7 days of incubation with 190 rpm agitation. The partial identification of the structure of the biosurfactant demonstrated the presence of an α,β-trehalose. The present study is the first report of the biosynthesis of this compound by F. fujikuroi, suggesting that the biosurfactant produced belongs to the class of trehalolipids.

Production and partial characterization of biosurfactant produced by Streptomyces sp. R1

The present study focused on developing a wild-type actinomycete isolate as a model for a non-pathogenic filamentous producer of biosurfactants. A total of 33 actinomycetes isolates were screened and their extracellular biosurfactants production was evaluated using olive oil as the main substrate. Out of 33 isolates, 32 showed positive results in the oil spreading technique (OST). All isolates showed good emulsification activity (E₂₄) ranging from 84.1 to 95.8%. Based on OST and E₂₄ values, isolate R1 was selected for further investigation in biosurfactant production in an agitated submerged fermentation. Phenotypic and genotypic analyses tentatively identified isolate R1 as a member of the Streptomyces genus. A submerged cultivation of Streptomyces sp. R1 was carried out in a 3-L stirred-tank bioreactor. The influence of impeller tip speed on volumetric oxygen transfer coefficient (k _L a), growth, cell morphology and biosurfactant production was observed. It was found that the maximum biosurfactant production, indicated by the lowest surface tension measurement (40.5 ± 0.05 dynes/cm) was obtained at highest k _L a value (50.94 h^-1) regardless of agitation speed. The partially purified biosurfactant was obtained at a concentration of 7.19 g L^-1, characterized as a lipopeptide biosurfactant and was found to be stable over a wide range of temperature (20-121 °C), pH (2-12) and salinity [5-20% (w/v) of NaCl].

Production, Characterization, and Application of Bacillus licheniformis W16 Biosurfactant in Enhancing Oil Recovery

The biosurfactant production by Bacillus licheniformis W16 and evaluation of biosurfactant based enhanced oil recovery (EOR) using core-flood under reservoir conditions were investigated. Previously reported nine different production media were screened for biosurfactant production, and two were further optimized with different carbon sources (glucose, sucrose, starch, cane molasses, or date molasses), as well as the strain was screened for biosurfactant production during the growth in different media. The biosurfactant reduced the surface tension and interfacial tension to 24.33 ± 0.57 mN m-1 and 2.47 ± 0.32 mN m-1 respectively within 72 h, at 40°C, and also altered the wettability of a hydrophobic surface by changing the contact angle from 55.67 ± 1.6 to 19.54°± 0.96°. The critical micelle dilution values of 4X were observed. The biosurfactants were characterized by different analytical techniques and identified as lipopeptide, similar to lichenysin-A. The biosurfactant was stable over wide range of extreme environmental conditions. The core flood experiments showed that the biosurfactant was able to enhance the oil recovery by 24-26% over residual oil saturation (Sor). The results highlight the potential application of lipopeptide biosurfactant in wettability alteration and microbial EOR processes.

Bioremediation of Heavy Crude Oil Contamination

Crude oil contamination is one of the major environmental concerns and it has drawn interest from researchers and industries. Heavy oils contain 24-64% saturates and aromatics, 14-39% resins and 11-45% asphaltene. Resins and asphaltenes mainly consist of naphthenic aromatic hydrocarbons with alicyclic chains which are the hardest to degrade. Crude oil biodegradation process, with its minimal energy need and environmentally friendly approach, presents an opportunity for bioremediation and as well for enhanced oil recovery to utilize heavy oil resources in an efficient manner. Biodegradation entails crude oil utilization as a carbon source for microorganisms that in turn change the physical properties of heavy crude oil by oxidizing aromatic rings, chelating metals and severing internal bonds/chains between molecules. Biodegradation does not necessarily lower quality of crude oil as there are cases where quality was improved. This paper provides information on heavy crude oil chemistry, bioremediation concept, biodegradation enzymes, cases of Microbial Enhanced heavy crude Oil Recovery (MEOR) and screening criteria towards a better understanding of the biodegradation application. Through the utilization of single microorganisms and consortia, researchers were able to biodegrade single pure hydrocarbon components, transform heavy crude oil fractions to lighter fractions, remove heavy metals and reduce viscosity of crude oil.

Lipopeptide production by Bacillus subtilis R1 and its possible applications

The possible application of a bacterial strain - Bacillus subtilis R1, isolated from an oil contaminated desert site in India, as biocontrol agent and its biosurfactant in microbial enhanced oil recovery are discussed. The biosurfactant production in minimal medium was carried out at different temperatures and salt concentrations, where it produced an efficient biosurfactant at 30-45°C and in presence of up to 7% salt. It significantly reduced the surface tension from 66±1.25mN/m to 29±0.85mN/m within 24h. In order to enhance the biosurfactant production, random mutagenesis of B. subtilis R1 was performed using chemical mutagen - ethyl methanesulfonate. Majority of the isolated 42 mutants showed biosurfactant production, but the difference was statistically insignificant as compared with parent strain R1. Therefore none of the mutants were selected for further study, and only parent strain R1 was studied. The biosurfactant was quite stable under harsh conditions for up to 10 days. The biosurfactant was extracted and characterized as similar to the lipopeptide group - surfactins and fengycin. The crude oil displacement experiments using biosurfactant broth in sand pack glass columns showed 33±1.25% additional oil recovery. The strain also showed inhibition of various plant pathogenic fungi on potato dextrose agar medium.

Kinetic and Structural Aspects of the Permeabilization of Biological and Model Membranes by Lichenysin

The various lichenysins produced by Bacillus licheniformis are anionic surfactants with interesting properties. Here it is shown that lichenysin caused hemolysis of human erythrocytes, which varied with lichenysin concentration in a sigmoidal manner. The release of K(+) from red blood cells induced by lichenysin preceded the leakage of hemoglobin, and in addition, hemolysis could be impeded by the presence of compounds in the external medium having a size larger than that of PEG 3350, indicating a colloid-osmotic mechanism for hemolysis. Lichenysin also caused permeabilization of model phospholipid membranes, which was a slow process with an initial lag period of 10-20 s observed for all lichenysin concentrations. A high cholesterol ratio in the membrane decreased the extent of leakage as compared to that of pure POPC, whereas at lower ratios the effect of cholesterol was the opposite, enhancing the extent of leakage. POPE was found to decrease the extent of leakage at all the concentrations assayed, and inclusion of DPPC resulted in a considerable increase in CF leakage extent. From this scenario it was concluded that lipid membrane composition plays a role in the target membrane selectivity of lichenysin. Molecular dynamics simulations indicated that lichenysin is well distributed along the bilayer, and Na(+) ions can penetrate inside the bilayer through the lichenysin molecules. The presence of lichenysin in the membrane increases the permeability of the membrane to hydrophilic molecules facilitating its flux across the lipid palisade. The results presented in this work contribute to understanding the molecular mechanisms that explain the biological actions of lichenysin related to biomembranes.

Sophorolipids Production by Candida bombicola ATCC 22214 and its Potential Application in Microbial Enhanced Oil Recovery

Biosurfactant production using Candida bombicola ATCC 22214, its characterization and potential applications in enhancing oil recovery were studied at laboratory scale. The seed media and the production media were standardized for optimal growth and biosurfactant production. The production media were tested with different carbon sources: glucose (2%w/v) and corn oil (10%v/v) added separately or concurrently. The samples were collected at 24 h interval up to 120 h and checked for growth (OD660), and biosurfactant production [surface tension (ST) and interfacial tension (IFT)]. The medium with both glucose and corn oil gave better biosurfactant production and reduced both ST and IFT to 28.56 + 0.42mN/m and 2.13 + 0.09mN/m, respectively within 72 h. The produced biosurfactant was quite stable at 13-15% salinity, pH range of 2-12, and at temperature up to 100°C. It also produced stable emulsions (%E24) with different hydrocarbons (pentane, hexane, heptane, tridecane, tetradecane, hexadecane, 1-methylnaphthalene, 2,2,4,4,6,8-heptamethylnonane, light and heavy crude oil). The produced biosurfactant was extracted using ethyl acetate and characterized as a mixture of sophorolipids (SPLs). The potential of SPLs in enhancing oil recovery was tested using core-flooding experiments under reservoir conditions, where additional 27.27% of residual oil (Sor) was recovered. This confirmed the potential of SPLs for applications in microbial enhanced oil recovery.