Purification and characterization of a surfactin-like molecule produced by Bacillus sp. H2O-1 and its antagonistic effect against sulfate reducing bacteria

Microbial lipopeptides: their pharmaceutical and biotechnological potential, applications, and way forward

As lead molecules, cyclic lipopeptides with antibacterial, antifungal, and antiviral properties have garnered a lot of attention in recent years. Because of their potential, cyclic lipopeptides have earned recognition as a significant class of antimicrobial compounds with applications in pharmacology and biotechnology. These lipopeptides, often with biosurfactant properties, are amphiphilic, consisting of a hydrophilic moiety, like a carboxyl group, peptide backbone, or carbohydrates, and a hydrophobic moiety, mostly a fatty acid. Besides, several lipopeptides also have cationic groups that play an important role in biological activities. Antimicrobial lipopeptides can be considered as possible substitutes for antibiotics that are conventional to address the current drug-resistant issues as pharmaceutical industries modify the parent antibiotic molecules to render them more effective against antibiotic-resistant bacteria and fungi, leading to the development of more resistant microbial strains. Bacillus species produce lipopeptides, which are secondary metabolites that are amphiphilic and are typically synthesized by non-ribosomal peptide synthetases (NRPSs). They have been identified as potential biocontrol agents as they exhibit a broad spectrum of antimicrobial activity. A further benefit of lipopeptides is that they can be produced and purified biotechnologically or biochemically in a sustainable manner using readily available, affordable, renewable sources without harming the environment. In this review, we discuss the biochemical and functional characterization of antifungal lipopeptides, as well as their various modes of action, method of production and purification (in brief), and potential applications as novel antibiotic agents.

Do biosurfactants as anti-biofilm agents have a future in industrial water systems?

Biofilms are bacterial communities embedded in exopolymeric substances that form on the surfaces of both man-made and natural structures. Biofilm formation in industrial water systems such as cooling towers results in biofouling and biocorrosion and poses a major health concern as well as an economic burden. Traditionally, biofilms in industrial water systems are treated with alternating doses of oxidizing and non-oxidizing biocides, but as resistance increases, higher biocide concentrations are needed. Using chemically synthesized surfactants in combination with biocides is also not a new idea; however, these surfactants are often not biodegradable and lead to accumulation in natural water reservoirs. Biosurfactants have become an essential bioeconomy product for diverse applications; however, reports of their use in combating biofilm-related problems in water management systems is limited to only a few studies. Biosurfactants are powerful anti-biofilm agents and can act as biocides as well as biodispersants. In laboratory settings, the efficacy of biosurfactants as anti-biofilm agents can range between 26% and 99.8%. For example, long-chain rhamnolipids isolated from Burkholderia thailandensis inhibit biofilm formation between 50% and 90%, while a lipopeptide biosurfactant from Bacillus amyloliquefaciens was able to inhibit biofilms up to 96% and 99%. Additionally, biosurfactants can disperse preformed biofilms up to 95.9%. The efficacy of antibiotics can also be increased by between 25% and 50% when combined with biosurfactants, as seen for the V9T14 biosurfactant co-formulated with ampicillin, cefazolin, and tobramycin. In this review, we discuss how biofilms are formed and if biosurfactants, as anti-biofilm agents, have a future in industrial water systems. We then summarize the reported mode of action for biosurfactant molecules and their functionality as biofilm dispersal agents. Finally, we highlight the application of biosurfactants in industrial water systems as anti-fouling and anti-corrosion agents.

Biosurfactant: an emerging tool for the petroleum industries

The petroleum sector is essential to supplying the world's energy demand, but it also involves numerous environmental problems, such as soil pollution and oil spills. The review explores biosurfactants' potential as a new tool for the petroleum sector. Comparing biosurfactants to their chemical equivalents reveals several advantages. They are ecologically sustainable solutions since they are renewable, nontoxic, and biodegradable. Biosurfactants are used in a variety of ways in the petroleum sector. They can improve the mobilization and extraction of trapped hydrocarbons during oil recovery procedures. By encouraging the dispersion and solubilization of hydrocarbons, biosurfactants also assist in the cleanup of oil spills and polluted locations by accelerating their breakdown by local microorganisms. The review gives insights into alternative methods for the petroleum industry that are more viable and cost-effective.

Inhibition of heterotrophic bacterial biofilm in the soil ferrosphere by Streptomyces spp. and Bacillus velezensis

The soil microbiome is involved in the processes of microbial corrosion, in particular, by the formation of biofilm. It has been proposed that an environmentally friendly solution to this corrosion might be through biological control. Bacillus velezensis NUChC C2b, Streptomyces gardneri ChNPU F3 and S. canus NUChC F2 were investigated as potentially 'green' biocides to prevent attachment to glass as a model surface and the formation of heterotrophic bacterial biofilm which participates in the corrosion process. Results showed high antagonistic and antibiofilm properties of S. gardneri ChNPU F3; which may be related to the formation of secondary antimicrobial metabolites by this strain. B. velezensis NUChC C2b and S. gardneri ChNPU F3 could be incorporated into green biocides - as components of antibiofilm agents that will protect material from bacterial corrosion or as agents that will prevent historical heritage damage.

Microbe Related Chemical Signalling and Its Application in Agriculture

The agriculture sector has been put under tremendous strain by the world’s growing population. The use of fertilizers and pesticides in conventional farming has had a negative impact on the environment and human health. Sustainable agriculture attempts to maintain productivity, while protecting the environment and feeding the global population. The importance of soil-dwelling microbial populations in overcoming these issues cannot be overstated. Various processes such as rhizospheric competence, antibiosis, release of enzymes, and induction of systemic resistance in host plants are all used by microbes to influence plant-microbe interactions. These processes are largely founded on chemical signalling. Producing, releasing, detecting, and responding to chemicals are all part of chemical signalling. Different microbes released distinct sorts of chemical signal molecules which interacts with the environment and hosts. Microbial chemicals affect symbiosis, virulence, competence, conjugation, antibiotic production, motility, sporulation, and biofilm growth, to name a few. We present an in-depth overview of chemical signalling between bacteria-bacteria, bacteria-fungi, and plant-microbe and the diverse roles played by these compounds in plant microbe interactions. These compounds’ current and potential uses and significance in agriculture have been highlighted.

Lipopeptide Biosurfactants from Bacillus spp.: Types, Production, Biological Activities, and Applications in Food

Biosurfactants are a functionally and structurally heterogeneous group of biomolecules produced by multiple filamentous fungi, yeast, and bacteria, and characterized by their distinct surface and emulsifying ability. The genus Bacillus is well studied for biosurfactant production as it produces various types of lipopeptides, for example, lichenysins, bacillomycin, fengycins, and surfactins. Bacillus lipopeptides possess a broad spectrum of biological activities such as antimicrobial, antitumor, immunosuppressant, and antidiabetic, in addition to their use in skincare. Moreover, Bacillus lipopeptides are also involved in various food products to increase the antimicrobial, surfactant, and emulsification impact. From the previously published articles, it can be concluded that biosurfactants have strong potential to be used in food, healthcare, and agriculture. In this review article, we discuss the versatile functions of lipopeptide Bacillus species with particular emphasis on the biological activities and their applications in food.

The Role of Serratomolide-like Amino Lipids Produced by Bacteria of Genus Serratia in Nematicidal Activity

Bursaphelenchus xylophilus, also known as pinewood nematode (PWN), is the pathogenic agent of pine wilt disease (PWD), which affects pine trees around the world. Infection spread globally through international wood commerce and locally by vector beetles, threatening the wood world economy. As climate changes, more countries are becoming susceptible to PWD and, to prevent disease spread and limit economic and ecological losses, better knowledge about this pathogenic agent is needed. Serratia strains, present in the endophytic community of pine trees and carried by PWN, may play an important role in PWD. This work aimed to better understand the interaction between Serratia strains and B. xylophilus and to assess the nematicidal potential of serratomolide-like molecules produced by Serratia strains. Serrawettin gene presence was evaluated in selected Serratia strains. Mortality tests were performed with bacteria supernatants, and extracted amino lipids, against Caenorhabditis elegans (model organism) and B. xylophilus to determine their nematicidal potential. Attraction tests were performed with C. elegans. Concentrated supernatants of Serratia strains with serratamolide-like lipopeptides were able to kill more than 77% of B. xylophilus after 72 h. Eight specific amino lipids showed a high nematicidal activity against B. xylophilus. We conclude that, for some Serratia strains, their supernatants and specific amino lipids showed nematicidal activity against B. xylophilus.

Purification and characterization of antibacterial surfactin isoforms produced by Bacillus velezensis SK

Bacillus velezensis SK having broad-spectrum antimicrobial activity has been isolated from soil. The efficient extraction of antimicrobial compounds produced in various mediums has been done using Diaion HP-20 resin. Further, characterization of an antimicrobial compound by TLC, FTIR, in-situ bioautography analysis revealed the presence of cyclic lipopeptides, which is then purified by the combination of silica gel, size exclusion, dual gradient, and RP-HPLC chromatography techniques. Growth kinetic studies showed that Bacillus velezensis SK produces a mixture of lipopeptides (1.33 gL^-1). The lipopeptide exhibits good pH (2-10) and temperature stability up to 80 °C. LC-ESI-MS analysis of partially purified lipopeptide identified variant of surfactin, further analysis of purified chromatographic fractions revealed the occurrence of most abundant C₁₅-surfactin homologues (m/z 1036.72 Da). The isolated surfactin exhibits good antimicrobial activity (1600 AU/ml) against drug-resistant food-born B. cereus and human pathogen Staphylococcus aureus. Hence, identified strain B. velezensis SK and its potent antibacterial surfactin lipopeptide could be used in various food and biomedical applications.

Bacillus velezensis H2O-1 surfactin efficiently maintains its interfacial properties in extreme conditions found in post-salt and pre-salt oil reservoirs

Biosurfactants are molecules with surfactant properties produced by microorganisms, and can be used in various industrial sectors, e.g., the oil industry. These molecules can be used in enhanced oil recovery (EOR) in the pre-salt and post-salt reservoirs, where conditions of temperature, pressure, and salinity are quite varied, requiring a study of the stability of these molecules under these conditions. Bacillus velezensis H2O-1 produces five different surfactin homologs with a fatty-acid chain ranging from C11 to C16 and with a high capacity to reduce surface (24.8 mN.m^-1) and interfacial tensions (1.5 and 0.8 8 mN.m^-1 using light, medium oil and n-hexadecane, respectively). The critical micellar concentration (CMC) was 38.7 mg.L^-1. Inversion wettability tests were carried out under the salinity conditions found in the post-salt (35 g.L^-1) and pre-salt (70 g.L^-1) reservoirs, in which it was observed that the surfactin reversed 100 % of the wettability of the calcite impregnated with light and medium oil. Using a central composite rotatable design, we demonstrated that surfactin maintained its interfacial properties when subjected simultaneously to extreme conditions of pressure, temperature and salinity commonly found in the post-salt (70 °C, 70 g.L^-1 and 27.58 MPa) and pre-salt (100 °C, 150 g.L^-1 and 48.2 MPa) layers. The results presented here highlight the efficiency and stability of H2O-1 surfactin in environmental conditions found in pre-salt and post-salt oil reservoirs.

Production of rhamnolipids by the Thermoanaerobacter sp. CM-CNRG TB177 strain isolated from an oil well in Mexico

This study aimed to produce and characterize biosurfactants using the Thermoanaerobacter sp. CM-CNRG TB177 strain isolated from an oil field in Mexico, as well as assessing the influence of different carbon and nitrogen sources on the capacity of the produced surfactant to reduce the surface tension of water. The thin-layer chromatography (TLC) revealed that the obtained extract corresponds to a mono-rhamnolipid; the results of the ultra-performance-liquid chromatography/mass spectrometry (UPLC/MS) analysis revealed that the Thermoanaerobacter sp. CM-CNRG TB177 strain produces a mixture of three rhamnolipids, whose masses correspond to mono-rhamnolipid. The rhamnolipids mixture obtained using 2.5% molasses as carbon source diminished the surface tension of water to 29.67 mNm^-1, indicating that the concentration of molasses influenced the capacity of the produced surfactant to reduce the surface tension of water. Also, the microorganism was not capable of growing in the absence of yeast extract as nitrogen source. To the best of our knowledge, the presented results describe for the first time the nature of the biosurfactant produced by a bacterium of the Thermoanaerobacter genus.Key points• Thermoanaerobacter sp. CM-CNRG TB177 produces biosurfactants, and its glycolipid nature is described for the first time.• The HPLC analysis revealed a mixture of three rhamnolipid congeners, and UPLC/MS analysis determined that two of the congeners are the rhamnolipids Rha-C8-C10 and Rha-C12-C10.• The lowest surface tension of 29.67 mNm^-1 was obtained with molasses as source of carbon at a 2.5% concentration.

Rhamnolipids and surfactin inhibit the growth or formation of oral bacterial biofilm

Background

Bacteria survive in various environments by forming biofilms. Bacterial biofilms often cause significant problems to medical instruments and industrial processes. Techniques to inhibit biofilm formation are essential and have wide applications. In this study, we evaluated the ability of two types of biosurfactants (rhamnolipids and surfactin) to inhibit growth and biofilm formation ability of oral pathogenic bacteria such as Aggregatibacter actinomycetemcomitans, Streptococcus mutans, and Streptococcus sanguinis.

Results

Rhamnolipids inhibited the growth and biofilm formation ability of all examined oral bacteria. Surfactin showed effective inhibition against S. sanguinis ATCC10556, but lower effects toward A. actinomycetemcomitans Y4 and S. mutans UA159. To corroborate these results, biofilms were observed by scanning electron microscopy (SEM) and confocal microscopy. The observations were largely in concordance with the biofilm assay results. We also attempted to determine the step in the biofilm formation process that was inhibited by biosurfactants. The results clearly demonstrated that rhamnolipids inhibit biofilm formation after the initiation process, however, they do not affect attachment or maturation.

Conclusions

Rhamnolipids inhibit oral bacterial growth and biofilm formation by A. actinomycetemcomitans Y4, and may serve as novel oral drug against localized invasive periodontitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-020-02034-9.

Biosurfactant-Mediated Membrane Depolarization Maintains Viability during Oxygen Depletion in Bacillus subtilis

The presence or absence of oxygen in the environment is a strong effector of cellular metabolism and physiology. Like many eukaryotes and some bacteria, Bacillus subtilis primarily utilizes oxygen during respiration to generate ATP. Despite the importance of oxygen for B. subtilis survival, we know little about how populations adapt to shifts in oxygen availability. Here, we find that when oxygen was depleted from stationary phase B. subtilis cultures, ∼90% of cells died while the remaining cells maintained colony-forming ability. We discover that production of the antimicrobial surfactin confers two oxygen-related fitness benefits: it increases aerobic growth yield by increasing oxygen diffusion, and it maintains viability during oxygen depletion by depolarizing the membrane. Strains unable to produce surfactin exhibited an ∼50-fold reduction in viability after oxygen depletion. Surfactin treatment of these cells led to membrane depolarization and reduced ATP production. Chemical and genetic perturbations that alter oxygen consumption or redox state support a model in which surfactin-mediated membrane depolarization maintains viability through slower oxygen consumption and/or a shift to a more reduced metabolic profile. These findings highlight the importance of membrane potential in regulating cell physiology and growth, and demonstrate that antimicrobials that depolarize cell membranes can benefit cells when the terminal electron acceptor in respiration is limiting. This foundational knowledge has deep implications for environmental microbiology, clinical anti-bacterial therapy, and industrial biotechnology.

Lesson from Ecotoxicity: Revisiting the Microbial Lipopeptides for the Management of Emerging Diseases for Crop Protection

Microorganisms area treasure in terms of theproduction of various bioactive compounds which are being explored in different arenas of applied sciences. In agriculture, microbes and their bioactive compounds are being utilized in growth promotion and health promotion withnutrient fortification and its acquisition. Exhaustive explorations are unraveling the vast diversity of microbialcompounds with their potential usage in solving multiferous problems incrop production. Lipopeptides are one of such microbial compounds which havestrong antimicrobial properties against different plant pathogens. These compounds are reported to be produced by bacteria, cyanobacteria, fungi, and few other microorganisms; however, genus Bacillus alone produces a majority of diverse lipopeptides. Lipopeptides are low molecular weight compounds which havemultiple industrial roles apart from being usedas biosurfactants and antimicrobials. In plant protection, lipopeptides have wide prospects owing totheirpore-forming ability in pathogens, siderophore activity, biofilm inhibition, and dislodging activity, preventing colonization bypathogens, antiviral activity, etc. Microbes with lipopeptides that haveall these actions are good biocontrol agents. Exploring these antimicrobial compounds could widen the vistasof biological pest control for existing and emerging plant pathogens. The broader diversity and strong antimicrobial behavior of lipopeptides could be a boon for dealing withcomplex pathosystems and controlling diseases of greater economic importance. Understanding which and how these compounds modulate the synthesis and production of defense-related biomolecules in the plants is a key question—the answer of whichneeds in-depth investigation. The present reviewprovides a comprehensive picture of important lipopeptides produced by plant microbiome, their isolation, characterization, mechanisms of disease control, behavior against phytopathogens to understand different aspects of antagonism, and potential prospects for future explorations as antimicrobial agents. Understanding and exploring the antimicrobial lipopeptides from bacteria and fungi could also open upan entire new arena of biopesticides for effective control of devastating plant diseases.

Chemical and biological dispersants differently affect the bacterial communities of uncontaminated and oil-contaminated marine water

The use of dispersants in marine environments is a common practice worldwide for oil spill remediation. While the effects of chemical dispersants have been extensively studied, those of biosurfactants, mainly surfactin that is considered one of the most effective surfactants produced by bacteria, have been less considered. We constructed microcosms containing marine water collected from Grumari beach (W_GB, Brazil) and from Schiermonnikoog beach (W_SI, The Netherlands) with the addition of oil (WO), Ultrasperse II plus oil (WOS), surfactin plus oil (WOB), and both dispersants (WS or WB) individually. In these treatments, the composition of bacterial communities and their predictive biodegradation potential were determined over time. High-throughput sequencing of the rrs gene encoding bacterial 16S rRNA revealed that Bacteroidetes (Flavobacteria class) and Proteobacteria (mainly Gammaproteobacteria and Alphaproteobacteria classes) were the most abundant phyla found among the W_GB and W_SI microbiomes, and the relative abundance of the bacterial types in the different microcosms varied based on the treatment applied. Non-metrical multidimensional scaling (NMDS) revealed a clear clustering based on the addition of oil and on the dispersant type added to the GB or SI microcosms, i.e., WB and WOB were separated from WS and WOS in both marine ecosystems studied. The potential presence of diverse enzymes involved in oil degradation was indicated by predictive bacterial metagenome reconstruction. The abundance of predicted genes for degradation of petroleum hydrocarbons increased more in surfactin-treated microcosms than those treated with Ultrasperse II, mainly in the marine water samples from Grumari beach.

Disinfectant-like activity of lipopeptide biosurfactant produced by Bacillus tequilensis strain SDS21

Antiseptics and disinfectants are widely applied for eliminating microorganisms. However, microorganisms dwelling in the biofilm are less susceptible and in some cases resistant to biocide treatment. The present study describes isolation and characterization of lipopeptide biosurfactant exhibiting disinfectant-like activity. Biosurfactant was produced by an endo-rhizospheric bacterium Bacillus tequilensis strain SDS21. Biosurfactant reduced the surface tension of water from 72 to 30 mN/m with CMC of 40 mg/l. The Liquid Chromatography-Mass Spectrometry analysis of biosurfactant suggested it to be a mixture of C₁₄, C₁₅, C₁₆ and C₁₇ surfactin homologues. The lipopeptide biosurfactant exhibited bactericidal activity against planktonic cells and biofilm residing sessile cells. The biosurfactant treatment eradicated more than 99% of bacterial biofilm present on polystyrene, glass and stainless steel surface. The biosurfactant retained its bactericidal and biofilm eradicating activities even after exposure to extreme conditions like high temperate and extreme pH. Unlike some of the commonly used disinfectant, biosurfactant retained its bactericidal and biofilm removing activity even in the hard water containing Mg²⁺ and Ca²⁺ ions. Thus, suggesting that biosurfactant produced by strain SDS21 can be used as a disinfectant or in disinfectant-like formulations effective against both planktonic and biofilm residing bacteria.

Recent Patents on Impact of Lipopeptide on the Biofilm Formation onto Titanium and Stainless Steel Surfaces

BACKGROUND

Numerous causes of infection in arthroplasties are related to biofilm formation on implant surfaces. In order to circumvent this problem, new alternatives to prevent bacterial adhesion biosurfactants-based are emerging due to low toxicity, biodegradability and antimicrobial activity of several biosurfactants. We revised all patents relating to biosurfactants of applicability in orthopedic implants.

METHODS

This work aims to evaluate the capability of a lipopeptide produced by Bacillus subtilis ATCC 19659 isolates acting as inhibitors of the adhesion of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 onto titanium and stainless steel surfaces and its antimicrobial activity.

RESULTS

The adhesion of the strains to the stainless-steel surface was higher than that of titanium. Preconditioning of titanium and stainless-steel surfaces with 10 mg mL-1 lipopeptide reduced the adhesion of E. coli by up to 93% and the adhesion of S. aureus by up to 99.9%, suggesting the strong potential of lipopeptides in the control of orthopedic infections. The minimal inhibitory concentration and minimum bactericidal concentration were 10 and 240 µg mL-1 for E. coli and S. aureus, respectively.

CONCLUSION

The lipopeptide produced by Bacillus subtilis ATCC 19659 presented high biotechnological application in human health against orthopedic implants infections.

Evaluation of biological and enzymatic quorum quencher coating additives to reduce biocorrosion of steel

Microbial colonization can be detrimental to the integrity of metal surfaces and lead to microbiologically influenced corrosion (MIC). Biocorrosion is a serious problem for aquatic and marine industries in the world. In Minnesota (USA), where this study was conducted, biocorrosion severely affects the maritime transportation industry. The anticorrosion activity of a variety of compounds, including chemical (magnesium peroxide) and biological (surfactin, capsaicin, and gramicidin) molecules were investigated as coating additives. We also evaluated a previously engineered, extremely stable, non-biocidal enzyme known to interfere in bacterial signaling, SsoPox (a quorum quenching lactonase). Experimental steel coupons were submerged in water from the Duluth Superior Harbor (DSH) for 8 weeks in the laboratory. Biocorrosion was evaluated by counting the number and the coverage of corrosion tubercles on coupons and also by ESEM imaging of the coupon surface. Three experimental coating additives significantly reduced the formation of corrosion tubercles: surfactin, magnesium peroxide and the quorum quenching lactonase by 31%, 36% and 50%, respectively. DNA sequence analysis of the V4 region of the bacterial 16S rRNA gene revealed that these decreases in corrosion were associated with significant changes in the composition of bacterial communities on the steel surfaces. These results demonstrate the potential of highly stable quorum quenching lactonases to provide a reliable, cost-effective method to treat steel structures and prevent biocorrosion.

Volatile organic compounds of Bacillus atrophaeus HAB-5 inhibit the growth of Colletotrichum gloeosporioides

The use of fungicides to control plant diseases creates a potential health risk. One alternative to this problem is the biological control, which has been succesfully applied to control plant diseases. Bacillus atrophaeus HAB-5 exhibits a high inhibitory acitivities against different fungal pathogens and suppresses them. The aim of current studies is to produce and identify the antifungal compounds produced by the strain HAB-5. We found that the submerge fermentation harvested from Luria-Bertani (LB) medium had the highest activity against Colletotrichum gloeosporioides. The petroleum ether crude extract was strongly bioactive and its activity was stable after heat treatment, pH treatment, illuminated light as well as ultra violet exposition. The antifungal compounds were purified using gel chromatography column. Based on Gas Chromatography-Mass Spectrometry (GC-MS) analysis, nineteen different volatile organic compounds (VOCs) were identified included the range of alkanes, alkenes, alcohols, and organics acid. Among these identified compounds, Chloroacetic acid, tetradecyl esters followed by Octadecane and Hexadecanoic acid, methyl ester showed antifungal activity against C. gloeosporioides. Our results clearly showed Chloroacetic acid, tetradecyl esters; Octadecane and Hexadecanoic acid, methyl ester are key inhibitory compounds produced by Bacillus atrophaeus HAB-5 against C. gloeosporioides.

Green biocide for mitigating sulfate-reducing bacteria influenced microbial corrosion

In the present investigation, Polyalthia longifolia plant extract (PLAE) was used as biocide to control corrosion in the presence of sulfate-reducing bacteria (SRB). Transmission electron microscopy showed the damage of SRB outer cell membrane which lead to cell destruction and disturbed membrane permeability. The scanning electron microscopy also confirmed the cell shrinkage due to green biocide, and energy-dispersive Fourier transform infra-red spectroscopy indicated the decrease in sulfide concentration in the presence of biocide. Potentiodynamic polarization of mild steel showed the lower in corrosion rate due to the decrease in cathodic reduction kinetics of SRB in the presence of biocide PLAE. The gravimetric mass loss also showed corrosion rate dropped from 0.064 millimeter per year (mm/year) to 0.013 mm/year with and without biocide. The present study showed that P. longifolia extract could be a novel biocide against the growth of the SRB to control corrosion in oil and gas industries.

Genome and transcriptome analysis of surfactin biosynthesis in Bacillus amyloliquefaciens MT45

Natural Bacillus isolates generate limited amounts of surfactin (<10% of their biomass), which functions as an antibiotic or signalling molecule in inter-/intra-specific interactions. However, overproduction of surfactin in Bacillus amyloliquefaciens MT45 was observed at a titre of 2.93 g/l, which is equivalent to half of the maximum biomass. To systemically unravel this efficient biosynthetic process, the genome and transcriptome of this bacterium were compared with those of B. amyloliquefaciens type strain DSM7^T. MT45 possesses a smaller genome while containing more unique transporters and resistance-associated genes. Comparative transcriptome analysis revealed notable enrichment of the surfactin synthesis pathway in MT45, including central carbon metabolism and fatty acid biosynthesis to provide sufficient quantities of building precursors. Most importantly, the modular surfactin synthase overexpressed (9 to 49-fold) in MT45 compared to DSM7^T suggested efficient surfactin assembly and resulted in the overproduction of surfactin. Furthermore, based on the expression trends observed in the transcriptome, there are multiple potential regulatory genes mediating the expression of surfactin synthase. Thus, the results of the present study provide new insights regarding the synthesis and regulation of surfactin in high-producing strain and enrich the genomic and transcriptomic resources available for B. amyloliquefaciens.

Biosurfactants: Promising Molecules for Petroleum Biotechnology Advances

The growing global demand for sustainable technologies that improves the efficiency of petrochemical processes in the oil industry has driven advances in petroleum biotechnology in recent years. Petroleum industry uses substantial amounts of petrochemical-based synthetic surfactants in its activities as mobilizing agents to increase the availability or recovery of hydrocarbons as well as many other applications related to extraction, treatment, cleaning, and transportation. However, biosurfactants have several potential applications for use across the oil processing chain and in the formulations of petrochemical products such as emulsifying/demulsifying agents, anticorrosive, biocides for sulfate-reducing bacteria, fuel formulation, extraction of bitumen from tar sands, and many other innovative applications. Due to their versatility and proven efficiency, biosurfactants are often presented as valuable versatile tools that can transform and modernize petroleum biotechnology in an attempt to provide a true picture of state of the art and directions or use in the oil industry. We believe that biosurfactants are going to have a significant role in many future applications in the oil industries and in this review therefore, we highlight recent important relevant applications, patents disclosures and potential future applications for biosurfactants in petroleum and related industries.

Review lipopeptides biosurfactants: Mean classes and new insights for industrial, biomedical, and environmental applications

Lipopeptides are microbial surface active compounds produced by a wide variety of bacteria, fungi, and yeast. They are characterized by high structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface, respectively. Surfactin, iturin, and fengycin of Bacillus subtilis are among the most popular lipopeptides. Lipopepetides can be applied in diverse domains as food and cosmetic industries for their emulsification/de-emulsification capacity, dispersing, foaming, moisturizing, and dispersing properties. Also, they are qualified as viscosity reducers, hydrocarbon solubilizing and mobilizing agents, and metal sequestering candidates for application in environment and bioremediation. Moreover, their ability to form pores and destabilize biological membrane permits their use as antimicrobial, hemolytic, antiviral, antitumor, and insecticide agents. Furthermore, lipopeptides can act at the surface and can modulate enzymes activity permitting the enhancement of the activity of certain enzymes ameliorating microbial process or the inhibition of certain other enzymes permitting their use as antifungal agents. This article will present a detailed classification of lipopeptides biosurfactant along with their producing strain and biological activities and will discuss their functional properties and related applications.

Biocontrol of geosmin-producing Streptomyces spp. by two Bacillus strains from Chinese liquor

Streptomyces spp. producing geosmin have been regarded as the most frequent and serious microbial contamination causing earthy off-flavor in Chinese liquor. It is therefore necessary to control the Streptomyces community during liquor fermentation. Biological control, using the native microbiota present in liquor making, appears to be a better solution than chemical methods. The objective of this study was to isolate native microbiota antagonistic toward Streptomyces spp. and then to evaluate the possible action mode of the antagonists. Fourteen Bacillus strains isolated from different Daqu (the fermentation starter) showed antagonistic activity against Streptomyces sampsonii, which is one of the dominant geosmin producers. Bacillus subtilis 2-16 and Bacillus amyloliquefaciens 1-45 from Maotai Daqu significantly inhibited the growth of S. sampsonii by 57.8% and 84.3% respectively, and effectively prevented the geosmin production in the simulated fermentation experiments (inoculation ratio 1:1). To probe the biocontrol mode, the ability of strain 2-16 and 1-45 to produce antimicrobial metabolites and to reduce geosmin in the fermentation system was investigated. Antimicrobial substances were identified as lipopeptides by ultra-performance liquid chromatography tandem electrospray ionization/quadrupole-time-of-flight mass spectrometry (UPLC-ESI/Q-TOF MS) and in vitro antibiotic assay. In addition, strains 2-16 and 1-45 were able to remove 45% and 15% of the geosmin respectively in the simulated solid-state fermentation. This study highlighted the potential of biocontrol, and how the use of native Bacillus species in Daqu could provide an eco-friendly method to prevent growth of Streptomyces spp. and geosmin contamination in Chinese liquor fermentation.

Exploiting the aerobic endospore-forming bacterial diversity in saline and hypersaline environments for biosurfactant production

Background

Biosurfactants are surface-active biomolecules with great applicability in the food, pharmaceutical and oil industries. Endospore-forming bacteria, which survive for long periods in harsh environments, are described as biosurfactant producers. Although the ubiquity of endospore-forming bacteria in saline and hypersaline environments is well known, studies on the diversity of the endospore-forming and biosurfactant-producing bacterial genera/species in these habitats are underrepresented.

Methods

In this study, the structure of endospore-forming bacterial communities in sediment/mud samples from Vermelha Lagoon, Massambaba, Dois Rios and Abraão Beaches (saline environments), as well as the Praia Seca salterns (hypersaline environments) was determined via denaturing gradient gel electrophoresis. Bacterial strains were isolated from these environmental samples and further identified using 16S rRNA gene sequencing. Strains presenting emulsification values higher than 30 % were grouped via BOX-PCR, and the culture supernatants of representative strains were subjected to high temperatures and to the presence of up to 20 % NaCl to test their emulsifying activities in these extreme conditions. Mass spectrometry analysis was used to demonstrate the presence of surfactin.

Results

A diverse endospore-forming bacterial community was observed in all environments. The 110 bacterial strains isolated from these environmental samples were molecularly identified as belonging to the genera Bacillus, Thalassobacillus, Halobacillus, Paenibacillus, Fictibacillus and Paenisporosarcina. Fifty-two strains showed emulsification values of at least 30%, and they were grouped into18 BOX groups. The stability of the emulsification values varied when the culture supernatants of representative strains were subjected to high temperatures and to the presence of up to 20% NaCl. The presence of surfactin was demonstrated in one of the most promising strains.

Conclusion

The environments studied can harbor endospore-forming bacteria capable of producing biosurfactants with biotechnological applications. Various endospore-forming bacterial genera/species are presented for the first time as biosurfactant producers.

Lipopeptides as the antifungal and antibacterial agents: applications in food safety and therapeutics

A lot of crops are destroyed by the phytopathogens such as fungi, bacteria, and yeast leading to economic losses to the farmers. Members of the Bacillus genus are considered as the factories for the production of biologically active molecules that are potential inhibitors of growth of phytopathogens. Plant diseases constitute an emerging threat to global food security. Many of the currently available antimicrobial agents for agriculture are highly toxic and nonbiodegradable and thus cause extended environmental pollution. Moreover, an increasing number of phytopathogens have developed resistance to antimicrobial agents. The lipopeptides have been tried as potent versatile weapons to deal with a variety of phytopathogens. All the three families of Bacillus lipopeptides, namely, Surfactins, Iturins and Fengycins, have been explored for their antagonistic activities towards a wide range of phytopathogens including bacteria, fungi, and oomycetes. Iturin and Fengycin have antifungal activities, while Surfactin has broad range of potent antibacterial activities and this has also been used as larvicidal agent. Interestingly, lipopeptides being the molecules of biological origin are environmentally acceptable.