Pontifactin, a new lipopeptide biosurfactant produced by a marine Pontibacter korlensis strain SBK-47: Purification, characterization and its biological evaluation

Bioformulation of Bacillus proteolyticus MITWPUB1 and its biosurfactant to control the growth of phytopathogen Sclerotium rolfsii for the crop Brassica juncea var local, as a sustainable approach

Bacillus proteolyticus MITWPUB1 is a potential producer of biosurfactants (BSs), and the organism is also found to be a producer of plant growth promoting traits, such as hydrogen cyanide and indole acetic acid (IAA), and a solubilizer of phosphate. The BSs were reportedly a blend of two classes, namely glycolipids and lipopeptides, as found by thin layer chromatography and Fourier-transform infrared spectroscopy analysis. Furthermore, semi-targeted metabolite profiling via liquid chromatography mass spectroscopy revealed the presence of phospholipids, lipopeptides, polyamines, IAA derivatives, and carotenoids. The BS showed dose-dependent antagonistic activity against Sclerotium rolfsii; scanning electron microscopy showed the effects of the BS on S. rolfsii in terms of mycelial deformations and reduced branching patterns. In vitro studies showed that the application of B. proteolyticus MITWPUB1 and its biosurfactant to seeds of Brassica juncea var local enhanced the seed germination rate. However, sawdust-carrier-based bioformulation with B. proteolyticus MITWPUB1 and its BS showed increased growth parameters for B. juncea var L. This study highlights a unique bioformulation combination that controls the growth of the phytopathogen S. rolfsii and enhances the plant growth of B. juncea var L. Bacillus proteolyticus MITWPUB1 was also shown for the first time to be a prominent BS producer with the ability to control the growth of the phytopathogen S. rolfsii.

Microbial anti-biofilms: types and mechanism of action

Biofilms have been recognized as a serious threat to public health as it protects microbes from antimicrobials, immune defence mechanisms, chemical treatments and nutritional stress. Biofilms are also a source of concern in industries and water treatment because their presence compromises the integrity of equipment. To overcome these problems, it is necessary to identify novel anti-biofilm compounds. Products of microorganisms have been identified as promising broad-spectrum anti-biofilm agents. These natural products include biosurfactants, antimicrobial peptides, enzymes and bioactive compounds. Anti-biofilm products of microbial origin are chemically diverse and possess a broad spectrum of activities against biofilms. The objective of this review is to give an overview of the different types of microbial anti-biofilm products and their mechanisms of action.

Polyphenols and their nanoformulations as potential antibiofilm agents against multidrug-resistant pathogens

The emergence of multidrug-resistant (MDR) pathogens is a major problem in the therapeutic management of infectious diseases. Among the bacterial resistance mechanisms is the development of an enveloped protein and polysaccharide-hydrated matrix called a biofilm. Polyphenolics have demonstrated beneficial antibacterial effects. Phenolic compounds mediate their antibiofilm effects via disruption of the bacterial membrane, deprivation of substrate, protein binding, binding to adhesion complex, viral fusion blockage and interactions with eukaryotic DNA. However, these compounds have limitations of chemical instability, low bioavailability, poor water solubility and short half-lives. Nanoformulations offer a promising solution to overcome these challenges by enhancing their antibacterial potential. This review summarizes the antibiofilm role of polyphenolics, their underlying mechanisms and their potential role as resistance-modifying agents.

Antibiofilm activity of marine microbial natural products: potential peptide- and polyketide-derived molecules from marine microbes toward targeting biofilm-forming pathogens

Controlling and treating biofilm-related infections is challenging because of the widespread presence of multidrug-resistant microbes. Biofilm, a naturally occurring matrix of microbial aggregates, has developed intricate and diverse resistance mechanisms against many currently used antibiotics. This poses a significant problem, especially for human health, including clinically chronic infectious diseases. Thus, there is an urgent need to search for and develop new and more effective antibiotics. As the marine environment is recognized as a promising reservoir of new biologically active molecules with potential pharmacological properties, marine natural products, particularly those of microbial origin, have emerged as a promising source of antibiofilm agents. Marine microbes represent an untapped source of secondary metabolites with antimicrobial activity. Furthermore, marine natural products, owing to their self-defense mechanisms and adaptation to harsh conditions, encompass a wide range of chemical compounds, including peptides and polyketides, which are primarily found in microbes. These molecules can be exploited to provide novel and unique structures for developing alternative antibiotics as effective antibiofilm agents. This review focuses on the possible antibiofilm mechanism of these marine microbial molecules against biofilm-forming pathogens. It provides an overview of biofilm development, its recalcitrant mode of action, strategies for the development of antibiofilm agents, and their assessments. The review also revisits some selected peptides and polyketides from marine microbes reported between 2016 and 2023, highlighting their moderate and considerable antibiofilm activities. Moreover, their antibiofilm mechanisms, such as adhesion modulation/inhibition targeting biofilm-forming pathogens, quorum sensing intervention and inhibition, and extracellular polymeric substance disruption, are highlighted herein.

Microbial surfactants: characteristics, production and broader application prospects in environment and industry

Microbial surfactants are green molecules with high surface activities having the most promising advantages over chemical surfactants including their ability to efficiently reducing surface and interfacial tension, nontoxic emulsion-based formulations, biocompatibility, biodegradability, simplicity of preparation from low cost materials such as residual by-products and renewable resources at large scales, effectiveness and stabilization under extreme conditions and broad spectrum antagonism of pathogens to be part of the biocontrol strategy. Thus, biosurfactants are universal tools of great current interest. The present work describes the major types and microbial origin of surfactants and their production optimization from agro-industrial wastes in the batch shake-flasks and bioreactor systems through solid-state and submerged fermentation industries. Various downstream strategies that had been developed to extract and purify biosurfactants are discussed. Further, the physicochemical properties and functional characteristics of biosurfactants open new future prospects for the development of efficient and eco-friendly commercially successful biotechnological product compounds with diverse potential applications in environment, industry, biomedicine, nanotechnology and energy-saving technology as well.

A comprehensive study on microbial-surfactants from bioproduction scale-up toward electrokinetics remediation of environmental pollutants: Challenges and perspectives

Currently, researchers have focused on electrokinetic (EK) bioremediation due to its potential to remove a wide-range of pollutants. Further, to improve their performance, synthetic surfactants are employed as effective additives because of their excellent solubility and mobility. Synthetic surfactants have an excessive position in industries since they are well-established, cheap, and easily available. Nevertheless, these surfactants have adverse environmental effects and could be detrimental to aquatic and terrestrial life. Owing to social and environmental awareness, there is a rising demand for bio-based surfactants in the global market, from environmental sustainability to public health, because of their excellent surface and interfacial activity, higher and stable emulsifying property, biodegradability, non- or low toxicity, better selectivity and specificity at extreme environmental conditions. Unfortunately, challenges to biosurfactants, like expensive raw materials, low yields, and purification processes, hinder their applicability to large-scale. To date, extensive research has already been conducted for production scale-up using multidisciplinary approaches. However, it is still essential to research and develop high-yielding bacteria for bioproduction through traditional and biotechnological advances to reduce production costs. Herein, this review evaluates the recent progress made on microbial-surfactants for bioproduction scale-up and provides detailed information on traditional and advanced genetic engineering approaches for cost-effective bioproduction. Furthermore, this study emphasized the role of electrokinetic (EK) bioremediation and discussed the application of BioS-mediated EK for various pollutants remediation.

Microbial surfactants: A journey from fundamentals to recent advances

Microbial surfactants are amphiphilic surface-active substances aid to reduce surface and interfacial tensions by accumulating between two fluid phases. They can be generically classified as low or high molecular weight biosurfactants based on their molecular weight, whilst overall chemical makeup determines whether they are neutral or anionic molecules. They demonstrate a variety of fundamental characteristics, including the lowering of surface tension, emulsification, adsorption, micelle formation, etc. Microbial genera like Bacillus spp., Pseudomonas spp., Candida spp., and Pseudozyma spp. are studied extensively for their production. The type of biosurfactant produced is reliant on the substrate utilized and the pathway pursued by the generating microorganisms. Some advantages of biosurfactants over synthetic surfactants comprise biodegradability, low toxicity, bioavailability, specificity of action, structural diversity, and effectiveness in harsh environments. Biosurfactants are physiologically crucial molecules for producing microorganisms which help the cells to grasp substrates in adverse conditions and also have antimicrobial, anti-adhesive, and antioxidant properties. Biosurfactants are in high demand as a potential product in industries like petroleum, cosmetics, detergents, agriculture, medicine, and food due to their beneficial properties. Biosurfactants are the significant natural biodegradable substances employed to replace the chemical surfactants on a global scale in order to make a cleaner and more sustainable environment.

Biosurfactant from Bacillus subtilis DS03: Properties and Application in Cleaning Out Place System in a Pilot Sausages Processing

Biosurfactants (BS) are amphiphilic molecules that align at the interface reducing the surface tension. BS production is developed as an alternative to synthetic surfactants because they are biodegradable, with low toxicity and high specificity. BS are versatile, and this research proposes using a biosurfactant crude extract (BCE) as part of cleaning products. This paper reported the BCE production from Bacillus subtilis DS03 using a medium with molasses. The BCE product was characterized by different physical and chemical tests under a wide pH range, high temperatures, and emulsifying properties showing successful results. The water surface tension of 72 mN/m was reduced to 34 mN/m with BCE, achieving a critical micelle concentration at 24.66 ppm. BCE was also applied to polystyrene surface as pre-treatment to avoid microbial biofilm development, showing inhibition in more than 90% of Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes above 2000 ppm BCE. The test continued using BCE as post-treatment to remove biofilms, reporting a significant reduction of 50.10% Escherichia coli, 55.77% Staphylococcus aureus, and 59.44% Listeria monocytogenes in a concentration higher than 250 ppm BCE. Finally, a comparison experiment was performed between sodium lauryl ether sulfate (SLES) and BCE (included in commercial formulation), reporting an efficient reduction with the mixtures. The results suggested that BCE is a promising ingredient for cleaning formulations with applications in industrial food applications.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.

A critical review on the environmental application of lipopeptide micelles

The importance of lipopeptide micelles in environmental applications has been highlighted. These vessels exhibit various sizes, shapes, and surface properties under different environmental conditions. An in-depth understanding of the tunable assembling behavior of biosurfactant micelles is of great importance for their applications. However, a systematic review of such behaviors with assorted micro/nano micellar structures under given environmental conditions, particularly under low temperature and high salinity, remains untapped. Such impacts on their environmental applications have yet to be summarized. This review tried to fill the knowledge gaps by providing a comprehensive summary of the recent knowledge advancement in genetically regulated lipopeptides production, micelles associated decontamination mechanisms in low temperature and high salinity environments, and up-to-date environmental applications. This work is expected to deliver valuable insights to guide lipopeptide design and discovery. The mechanisms concluded in this study could inspire the forthcoming research efforts in the advanced environmental application of lipopeptide micelles.

Enhanced bioremediation of diesel oil-contaminated seawater by a biochar-immobilized biosurfactant-producing bacteria Vibrio sp. LQ2 isolated from cold seep sediment

This study investigated the effect of immobilized biosurfactant-producing bacteria on the bioremediation of diesel oil-contaminated seawater. Initially, a biosurfactant-producing bacterium, LQ2, was isolated from a marine cold-seep region, and identified as Vibrio sp. The biosurfactant produced by LQ2 was characterized as a phospholipid, exhibiting high surface activity with strong stability. Meanwhile, the inoculation of biochar-immobilized LQ2 demonstrated superior efficiency in removing diesel oil (94.7%, reduction from 169.2 mg to 8.91 mg) over a seven-day period compared to free-cell culture (54.4%), through both biodegradation and adsorption. In addition, the microbial growth and activity were greatly enhanced with the addition of immobilized LQ2. Further experiment showed that degradation-related genes, alkB and CYP450-1, were 3.8 and 15.2 times higher in the immobilized LQ2 treatment, respectively, than those in the free cell treatment. The findings obtained in this study suggest the feasibility of applying immobilized biosurfactant-producing bacteria, namely LQ2, in treating diesel oil-contaminated seawater.

Statistical optimization of medium components for biosurfactant production by Pseudomonas guguanensis D30

Biosurfactant production by Pseudomonas guguanensis D30 was reported using mineral oil in submerged condition. Twelve medium components were tested at two levels by Plackett-Burman design, among them, mineral oil, yeast extract, peptone, MgSO₄, and CaCl₂ found significant on the basis of emulsification index. These five significant components were further optimized through central composite design (CCD). The experimental design was successfully used for regression analysis and the significant model suggested the solution of 10% (v/v) mineral oil, 3.0 g/L (w/v) yeast extract and 0.2 g/L (w/v) peptone for 13.14 g/L predicted biosurfactant production. We kept the suggested concentrations of medium components and got 13.34 ± 0.08 g/L biosurfactant production, which is almost double the conventional one-factor-at-a-time production (7.126 ± 0.12 g/L). It reduced the surface tension of the medium up to 28 ± 1.2 mN/m. We found ethyl acetate a suitable solvent for biosurfactant extraction amongst methanol, chloroform, and methanol:chloroform. The partially purified biosurfactant was chemically characterized as lipopeptide by Fourier transform infrared spectroscopy (FT-IR).

Analysis of surfactants by mass spectrometry: Coming to grips with their diversity

Surfactants are surface-active agents widely used in numerous applications in our daily lives as personal care products, domestic, and industrial detergents. To determine complex mixtures of surfactants and their degradation products, unselective and rather insensitive methods, based on colorimetric and complexometric analyses are no longer employable. Analytical methodologies able to determine low concentration levels of surfactants and closely related compounds in complex matrices are required. The recent introduction of robust, sensitive, and selective mass spectrometry (MS) techniques has led to the rapid expansion of the surfactant research field including complex mixtures of isomers, oligomers, and homologues of surfactants as well as their chemically and biodegradation products at trace levels. In this review, emphasis is given to the state-of-the-art MS-based analysis of surfactants and their degradation products with an overview of the current research landscape from traditional methods involving hyphenate techniques (gas chromatography-MS and liquid chromatography-MS) to the most innovative approaches, based on high-resolution MS. Finally, we outline a detailed explanation on the utilization of MS for mechanistic purposes, such as the study of micelle formation in different solvents.

Microbial Biosurfactant: A New Frontier for Sustainable Agriculture and Pharmaceutical Industries

In the current scenario of changing climatic conditions and the rising global population, there is an urgent need to explore novel, efficient, and economical natural products for the benefit of humankind. Biosurfactants are one of the latest explored microbial synthesized biomolecules that have been used in numerous fields, including agriculture, pharmaceuticals, cosmetics, food processing, and environment-cleaning industries, as a source of raw materials, for the lubrication, wetting, foaming, emulsions formulations, and as stabilizing dispersions. The amphiphilic nature of biosurfactants have shown to be a great advantage, distributing themselves into two immiscible surfaces by reducing the interfacial surface tension and increasing the solubility of hydrophobic compounds. Furthermore, their eco-friendly nature, low or even no toxic nature, durability at higher temperatures, and ability to withstand a wide range of pH fluctuations make microbial surfactants preferable compared to their chemical counterparts. Additionally, biosurfactants can obviate the oxidation flow by eliciting antioxidant properties, antimicrobial and anticancer activities, and drug delivery systems, further broadening their applicability in the food and pharmaceutical industries. Nowadays, biosurfactants have been broadly utilized to improve the soil quality by improving the concentration of trace elements and have either been mixed with pesticides or applied singly on the plant surfaces for plant disease management. In the present review, we summarize the latest research on microbial synthesized biosurfactant compounds, the limiting factors of biosurfactant production, their application in improving soil quality and plant disease management, and their use as antioxidant or antimicrobial compounds in the pharmaceutical industries.

Surfactants of microbial origin as antibiofilm agents

The microbial world provides new energy sources and many various 'green' chemicals. One type of chemicals produced by microorganisms is the biosurfactant group. Biosurfactants are universal molecules, exhibiting surface properties often accompanied by desired biological activity. Biosurfactants are considered to be environmentally 'friendly' due to their low toxicity and biodegradable nature. These compounds have unique features and therefore they can find potential applications in many different industries, ranging from biotechnology to environmental remediation technologies. Antibacterial and antifungal activities make them relevant for applications as inhibitory agents against microbial biofilm. This review covers the current knowledge and the recent advances in the field of biosurfactants as antibiofilm agents.

A gelatinized lipopeptide diet effectively modulates immune response, disease resistance and gut microbiome in Penaeus vannamei challenged with Vibrio parahaemolyticus

Penaeus vannamei is one of the most economically vital shrimp globally, but infectious diseases have hampered its proper production and supply. As antibiotics pose a huge threat to the environment and humankind, it is essential to seek an alternative strategy to overcome infection and ensure proper culture and production. The present study investigates the effect of an anti-infective biosurfactant derivative lipopeptide MSA31 produced by a marine bacterium on the growth performance, disease resistance, and the gut microbiome of P. vannamei when challenged with pathogenic Vibrio parahaemolyticus SF14. The shrimp were fed with a commercial and lipopeptide formulated diet for 60 days and the growth performance was analyzed. The lipopeptide fed shrimp group showed enhanced growth performance and specific growth rate with improved weight gain than the control group. The challenge experiment showed that the survival rate was significant in the lipopeptide fed group compared to the control group. The results revealed 100% mortality in the control group at the end of 12 h of challenge, while 50% of the lipopeptide diet-fed group survived 24 h, which indicates the enhanced disease resistance in shrimp fed with a lipopeptide diet. The test group also showed higher levels of digestive and immune enzymes, which suggests that the lipopeptide diet could positively modulate the digestive and immune activity of the shrimp. The gut microbiome profiling by Illumina high-throughput sequencing revealed that the most abundant genera in the lipopeptide diet-fed group were Adhaeribacter, Acidothermus, Brevibacillus, Candidatus, Mycobacterium, Rodopila, and Streptomyces, while opportunistic pathogens such as Streptococcus, Escherichia, Klebsiella, Neisseria, Rhizobium, and Salmonella were abundant in the control diet-fed shrimp. Also, lipopeptide diet-fed shrimp were found to have a high abundance of ammonia and nitrogen oxidizing bacteria, which are essential pollutant degraders. Therefore, the study reveals that the dietary supplementation of lipopeptide in shrimp aquaculture could positively modulate the gut microbiome and enhance the shrimp's overall health and immunity in an eco-friendly manner.

Marine Microbial-Derived Antibiotics and Biosurfactants as Potential New Agents against Catheter-Associated Urinary Tract Infections

Catheter-associated urinary tract infections (CAUTIs) are among the leading nosocomial infections in the world and have led to the extensive study of various strategies to prevent infection. However, despite an abundance of anti-infection materials having been studied over the last forty-five years, only a few types have come into clinical use, providing an insignificant reduction in CAUTIs. In recent decades, marine resources have emerged as an unexplored area of opportunity offering huge potential in discovering novel bioactive materials to combat human diseases. Some of these materials, such as antimicrobial compounds and biosurfactants synthesized by marine microorganisms, exhibit potent antimicrobial, antiadhesive and antibiofilm activity against a broad spectrum of uropathogens (including multidrug-resistant pathogens) that could be potentially used in urinary catheters to eradicate CAUTIs. This paper summarizes information on the most relevant materials that have been obtained from marine-derived microorganisms over the last decade and discusses their potential as new agents against CAUTIs, providing a prospective proposal for researchers.

A review on new aspects of lipopeptide biosurfactant: Types, production, properties and its application in the bioremediation process

Nowadays, the worldwide search regarding renewable products from natural resources is increasing due to the toxicity of chemical counterparts. Biosurfactants are surface-active compounds that contain several physiological functions that are used in industries like food, pharmaceutical, petroleum and agriculture. Microbial lipopeptides have gained more attention among the researchers for their low toxicity, efficient action and good biodegradability when compared with other surfactants. Because of their versatile properties, lipopeptide compounds are utilized in the remediation of organic and inorganic pollutants. This review presented a depth evaluation of lipopeptide surfactants in the bioremediation process and their properties to maintain a sustainable environment. Lipopeptide can acts as a replacement to chemical surfactants only if they meet industrial-scale production and low-cost substrates. This review also demonstrated the production of a lipopeptide biosurfactant from a low-cost substrate and depicted plausible techniques to manage the substrate residues to determine its ability in the different applications particularly in the bioremediation process.

Natural Anti-biofilm Agents: Strategies to Control Biofilm-Forming Pathogens

Pathogenic microorganisms and their chronic pathogenicity are significant concerns in biomedical research. Biofilm-linked persistent infections are not easy to treat due to resident multidrug-resistant microbes. Low efficiency of various treatments and in vivo toxicity of available antibiotics drive the researchers toward the discovery of many effective natural anti-biofilm agents. Natural extracts and natural product-based anti-biofilm agents are more efficient than the chemically synthesized counterparts with lesser side effects. The present review primarily focuses on various natural anti-biofilm agents, i.e., phytochemicals, biosurfactants, antimicrobial peptides, and microbial enzymes along with their sources, mechanism of action via interfering in the quorum-sensing pathways, disruption of extracellular polymeric substance, adhesion mechanism, and their inhibitory concentrations existing in literature so far. This study provides a better understanding that a particular natural anti-biofilm molecule exhibits a different mode of actions and biofilm inhibitory activity against more than one pathogenic species. This information can be exploited further to improve the therapeutic strategy by a combination of more than one natural anti-biofilm compounds from diverse sources.

Exploring Antifouling Activity of Biosurfactants Producing Marine Bacteria Isolated from Gulf of California

Biofouling causes major problems and economic losses to marine and shipping industries. In the search for new antifouling agents, marine bacteria with biosurfactants production capability can be an excellent option, due to the amphipathic surface-active characteristic that confers antimicrobial and antibiofilm activities. The aim of this study was to evaluate the antifouling activity of biosurfactants producing marine bacteria from the Gulf of California. The cell free culture supernatant (CFCS) of Bacillus niabensis (S-69), Ralstonia sp. (S-74) (isolated from marine sediment) and of B. niabensis (My-30) (bacteria associated to the sponge Mycale ramulosa) were screened for production of biosurfactants (using hemolysis and drop collapse test, oil displacement and emulsifying activity). The toxicity and antifouling activity were evaluated against biofoulers (bacteria forming biofilm and macrofoulers) both in laboratory and field assays. The results indicate that all bacteria were biosurfactant producers, but the higher capability was shown by B. niabensis (My-30) with high emulsifying properties (E24) of 71%. The CFCS showed moderate toxicity but were considered non-toxic against Artemia franciscana at low concentrations. In the antifouling assay, the CFCS of both strains of B. niabensis showed the best results for the reduction of the biofilm formation (up 50%) against all Gram-positive bacteria and most Gram-negative bacteria with low concentrations. In the field assay, the CFCS of B. niabensis (My-30) led to the reduction of 30% of biofouling compared to the control. The results indicate that the biosurfactant produced by B. niabensis (My-30) has promising antifouling activity.

Production of biosurfactant by Bacillus subtilis RSL-2 isolated from sludge and biosurfactant mediated degradation of oil

This study aims to unveil the effect of biosurfactant as stimulant in crude oil bioremediation. Isolated oil-degrading strain, B. subtilis RSL 2 was optimized for the maximum oil degradation and biosurfactant production using Response surface methodology. The produced biosurfactant was characterized and investigated for its effect on microbial oil degradation in two modes (a) sequential and (b) simultaneous. The strain produced 3.5 g/L of biosurfactant at pH 4.0, 25 °C, using 1 g/L crude oil as the only C-source in 7 days, which was characterized as lipopeptide with a critical micelle concentration (CMC) of 0.5 g/L. The biosurfactant improved surface wettability of a hydrophobic substrate i.e. increased surface energy from 30 ± 1 to 35 ± 1 mJ/m². Further, the simultaneous feed of biosurfactant at 0.5 CMC enhanced oil biodegradation (72%) and biosurfactant production (5.2 g/L) by about 1.6 times than the sequential mode due to improvement in mobilization of oil thus making it more bioavailable.

Marine-Derived Surface Active Agents: Health-Promoting Properties and Blue Biotechnology-Based Applications

Surface active agents are characterized for their capacity to adsorb to fluid and solid-water interfaces. They can be classified as surfactants and emulsifiers based on their molecular weight (MW) and properties. Over the years, the chemical surfactant industry has been rapidly increasing to meet consumer demands. Consequently, such a boost has led to the search for more sustainable and biodegradable alternatives, as chemical surfactants are non-biodegradable, thus causing an adverse effect on the environment. To these ends, many microbial and/or marine-derived molecules have been shown to possess various biological properties that could allow manufacturers to make additional health-promoting claims for their products. Our aim, in this review article, is to provide up to date information of critical health-promoting properties of these molecules and their use in blue-based biotechnology (i.e., biotechnology using aquatic organisms) with a focus on food, cosmetic and pharmaceutical/biomedical applications.

Construction of a hydrocarbon-degrading consortium and characterization of two new lipopeptides biosurfactants

Apparent solubility and bioavailability of hydrophobic compounds are the major problems in the bioremediation process, which could be overcome by the bacteria capable of biosurfactant production and concurrent hydrocarbon degradation. In this work, we constructed an artificial bacterial consortium containing Lysinibacillus, Paenibacillus, Gordonia and Cupriavidus spp. from glyceryl tributyrate enriched bacteria collected from the non-contaminated site. The consortium was capable of using common raw materials (olive oil, paraffin oil, and glycerol) and polyaromatic hydrocarbons pollutants (naphthalene and anthracene) as the sole carbon source with simultaneous biosurfactant production. Two new lipopeptide isoforms, containing heptapeptide and lipid moieties, were structurally elucidated by LC-MS/MS, FTIR, NMR and molecular networking analysis. Our findings indicate that hydrocarbons degradation and biosurfactant production is an intrinsic property of non-contaminated soil community. Interestingly, we observed the hyper chemotactic activity of Lysinibacillus strains towards glyceryl tributyrate, which has not been reported before. The study may deepen our understanding of microbial strains and consortium with the potential to be used for bioremediation of hydrocarbons contaminated environments.

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.

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

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

Marine bacteria as source of antimicrobial compounds

The marine environment encompasses a huge biological diversity and can be considered as an underexplored location for prospecting bioactive molecules. In this review, the current state of art about antimicrobial molecules from marine bacteria has been summarized considering the main phylum and sources evolved in a marine environment. Considering the last two decades, we have found as most studied group of bacteria producers of substances with antimicrobial activity is the Firmicutes phylum, in particular strains of the Bacillus genus. The reason for that can be attributed to the difficult cultivation of typical Actinobacteria from a marine sediment, whose members are the major producers of antimicrobial substances in land environments. However, a reversed trend has been observed in recent years with an increasing number of reports settling on Actinobacteria. Great diversity of chemical structures have been identified, such as fijimicyns and lynamicyns from Actinomycetes and macrolactins produced by Bacillus.

Salinity and Time Can Alter Epibacterial Communities of an Invasive Seaweed

The establishment of epibacterial communities is fundamental to seaweed health and fitness, in modulating ecological interactions and may also facilitate adaptation to new environments. Abiotic factors like salinity can determine bacterial abundance, growth and community composition. However, influence of salinity as a driver of epibacterial community composition (until species level) has not been investigated for seaweeds and especially under long time scales. We also do not know how abiotic stressors may influence the 'core' bacterial species of seaweeds. Following an initial (immediately after field collection) sampling of epibacterial community of an invasive red seaweed Agarophyton vermicullophylum, we conducted a long term mesocosm experiment for 5 months, to examine the influence of three different salinities (low, medium and high) at two different time points (3 months after start of experiment and 5 months, i.e., at the end of experiment) on the epibacterial community richness and composition of Agarophyton. Metagenomic sequencing showed that epibacterial communities changed significantly according to salinity and time points sampled. Epibacterial richness was significantly different between low and high salinities at both time points. Epibacterial richness also varied significantly between 3 months (after start of experiment) and 5 months (end of experiment) within low, medium and high salinity level. Irrespective of salinity levels and time points sampled 727 taxa consistently appeared in all Agarophyton samples hinting at the presence of core bacterial species on the surface of the alga. Our results indicate that both salinity and time can be major driving forces in structuring epibacterial communities of seaweeds with respect to richness and β-diversity. We highlight the necessity of conducting long term experiments allowing us to detect and understand epibacterial succession over time on seaweeds.

Advanced strategies for combating bacterial biofilms

Biofilms are communities of microorganisms that are formed on and attached to living or nonliving surfaces and are surrounded by an extracellular polymeric material. Biofilm formation enjoys several advantages over the pathogens in the colonization process of medical devices and patients' organs. Unlike planktonic cells, biofilms have high intrinsic resistance to antibiotics and sanitizers, and overcoming them is a significant problematic challenge in the medical and food industries. There are no approved treatments to specifically target biofilms. Thus, it is required to study and present innovative and effective methods to combat a bacterial biofilm. In this review, several strategies have been discussed for combating bacterial biofilms to improve healthcare, food safety, and industrial process.

Desorption and solubilization of anthracene by a rhamnolipid biosurfactant from Rhodococcus fascians

The rhamnolipid biosurfactant-producing bacterium, strain SDRB-G7, was isolated from the sediment of Sindu-ri beach and identified as Rhodococcus fascians based on a phylogenetic analysis. Optimal activity, with the highest yield (2.441 g/L) and surface tension-reducing activity (24.38 mN/m), was observed when the cells were grown on olive oil as their sole source of carbon at pH 8.0. The rhamnolipid biosurfactant showed environmental stability at a variety of NaCl concentrations (2-20%) and pH values (2-12) even under acidic conditions. Of the initial anthracene, 66% was solubilized by 100% crude biosurfactant. Furthermore, 100% crude biosurfactant desorbed 81% of the anthracene in sediment into the aqueous phase. These results suggest that the rhamnolipid biosurfactant produced from R. fascians SDRB-G7 is a promising candidate for polycyclic aromatic hydrocarbon (PAH) removal from the sediment and can be an effective agent for processes that bioremediate PAHs such as surfactant-enhanced remediation. PRACTITIONER POINTS: Biosurfactants can accelerate desorption of PAHs and improve their solubility. BS-producing R. fascians SDRB-G7 was selected by screening of biochemical tests. Solubility of anthracene was enhanced by rhamnolipid produced by strain SDRB-G7. Microbial surfactant is a promising alternative for bioremediation of PAH-polluted sites.

Marine Biosurfactants: Biosynthesis, Structural Diversity and Biotechnological Applications

Biosurfactants are amphiphilic secondary metabolites produced by microorganisms. Marine bacteria have recently emerged as a rich source for these natural products which exhibit surface-active properties, making them useful for diverse applications such as detergents, wetting and foaming agents, solubilisers, emulsifiers and dispersants. Although precise structural data are often lacking, the already available information deduced from biochemical analyses and genome sequences of marine microbes indicates a high structural diversity including a broad spectrum of fatty acid derivatives, lipoamino acids, lipopeptides and glycolipids. This review aims to summarise biosyntheses and structures with an emphasis on low molecular weight biosurfactants produced by marine microorganisms and describes various biotechnological applications with special emphasis on their role in the bioremediation of oil-contaminated environments. Furthermore, novel exploitation strategies are suggested in an attempt to extend the existing biosurfactant portfolio.

Antioxidant, antibacterial, and anti-adhesive activities of biosurfactants isolated from Bacillus strains

Biosurfactants are surface-active compounds that display a range of physiological functions. The present study investigated the antioxidant, antimicrobial, and anti-adhesive or anti-biofilm potential of biosurfactants isolated from Bacillus subtilis VSG4 and Bacillus licheniformis VS16. The antioxidant activity of the biosurfactants was studied in vitro using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals. At 5 mg/mL of the biosurfactant concentration, the scavenging of DPPH and hydroxyl radicals was found to be between 69.1-73.5% and 63.3-69.8%, respectively. The biosurfactants also displayed significant antibacterial activities against both Gram-positive and Gram-negative bacteria. The anti-adhesive activities of the biosurfactants were evaluated against Staphylococcus aureus ATCC 29523, Salmonella typhimurium ATCC 19430, and Bacillus cereus ATCC 11778. The biosurfactants exhibited anti-adhesive activity, even at concentrations of 3-5 mg/mL. Moreover, both biosurfactants displayed notable anti-biofilm activities with a biofilm eradication percentage ranging from 63.9 to 80.03% for VSG4 biosurfactant, and from 61.1-68.4% for VS16 biosurfactant. Furthermore, VSG4 biosurfactant exhibited emulsification and surface tension stability over a wide range of pH (4-10) and temperature up to 100 °C. These results show that VSG4 and VS16 biosurfactants can be potentially used as natural antioxidants, antimicrobials, and/or anti-adhesive agents for food and biomedical applications.

Isolation and characterization of kurstakin and surfactin isoforms produced by Enterobacter cloacae C3 strain

In this work, the extraction, structural analysis, and identification as well as antimicrobial, anti-adhesive, and antibiofilm activities of lipopeptides produced by Enterobacter cloacae C3 strain were studied. A combination of chromatographic and spectroscopic techniques offers opportunities for a better characterization of the biosurfactant structure. Thin layer chromatography (TLC) and HPLC for amino acid composition determination are used. Efficient spectroscopic techniques have been utilized for investigations on the biochemical structure of biosurfactants, such as Fourier transform infrared (FT-IR) spectroscopy and mass spectrometry analysis. This is the first work describing the production of different isoforms belonging to kurstakin and surfactin families by E cloacae strain. Three kurstakin homologues differing by the fatty acid chain length from C₁₀ to C₁₂ were detected. The spectrum of lipopeptides belonging to surfactin family contains various isoforms differing by the fatty acid chain length as well as the amino acids at positions four and seven. Lipopeptide C3 extract exhibited important antibacterial activity against Gram-positive and Gram-negative bacteria, antifungal activity, and interesting anti-adhesive and disruptive properties against biofilm formation by human pathogenic bacterial strains: Salmonella typhimurium, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus cereus, and Candida albicans.

Gram-negative bacilli-derived peptide antibiotics developed since 2000

Gram-negative bacilli such as Pseudomonas spp., Pseudoalteromonas sp., Angiococcus sp., Archangium sp., Burkholderia spp., Chromobacterium sp., Chondromyces sp., Cystobacter sp., Jahnella sp., Janthinobacterium sp., Lysobacter spp., Paraliomyxa sp., Photobacterium spp., Photorhabdus sp., Pontibacter sp., Ruegeria sp., Serratia sp., Sorangium sp., Sphingomonas sp., and Xenorhabdus spp. produce an enormous array of short peptides of 30 residues or fewer that are potential pharmaceutical drugs and/or biocontrol agents. The need for novel lead antibiotic compounds is urgent due to increasing drug resistance, and this review summarises 150 Gram-negative bacilli-derived compounds reported since 2000, including 40 cyclic lipopeptides from Pseudomonas spp.; nine aromatic peptides; eight glycopeptides; 45 different cyclic lipopeptides; 24 linear lipopeptides; eight thiopeptides; one lasso peptide; ten typical cyclic peptides; and five standard linear peptides. The current and potential therapeutic applications of these peptides, including structures and antituberculotic, anti-cyanobacterial, antifungal, antibacterial, antiviral, insecticidal, and antiprotozoal activities are discussed.

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

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

Marine natural products

Covering: 2016. Previous review: Nat. Prod. Rep., 2017, 34, 235-294This review covers the literature published in 2016 for marine natural products (MNPs), with 757 citations (643 for the period January to December 2016) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1277 in 432 papers for 2016), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included.

Antioxidant properties, antimicrobial and anti-adhesive activities of DCS1 lipopeptides from Bacillus methylotrophicus DCS1

BACKGROUND

The present work aims to investigate the antioxidant and antimicrobial activities as well as the potential of DCS1 lipopeptides produced by Bacillus methylotrophicus DCS1 strain at inhibition and disruption of biofilm formation.

RESULTS

The produced biosurfactants were characterized as lipopeptides molecules by using thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FT-IR). The DCS1 lipopeptides were assayed for their antioxidant activity through five different tests. The scavenging effect on DPPH radicals at a concentration of 1 mg mL^-1 was 80.6%. The reducing power reached a maximum value of 3.0 (OD_{700 nm}) at 2 mg mL^-1. Moreover, the DCS1 lipopeptides exhibited a strong inhibition of β-carotene bleaching by linoleic acid assay with 80.8% at 1 mg mL^-1 and showed good chelating ability and lipid peroxidation inhibition. The in vitro antimicrobial activity of DCS1 lipopeptides showed that they display significant antibacterial and antifungal activities. The anti-adhesive activity of DCS1 lipopeptides was evaluated against several pathogenic microorganisms. The lipopeptides showed excellent anti-adhesive activity, even at low concentrations, in a polystyrene surface pre-treatment against all the microorganisms tested. Further, they can disrupt performed biofilms.

CONCLUSION

This study shows the potentiality of DCS1 lipopeptides as natural antioxidants, antimicrobial and/or anti-adhesive agent for several biomedical and industrial applications.

Aneurinifactin, a new lipopeptide biosurfactant produced by a marine Aneurinibacillus aneurinilyticus SBP-11 isolated from Gulf of Mannar: Purification, characterization and its biological evaluation

Biosurfactants are microbial-derived amphiphilic molecules having hydrophobic and hydrophilic moieties produced by bacteria, fungi, yeasts and algae and are extracellular or cell wall-associated compounds. In an ongoing survey for bioactive microbial metabolites from microbes isolated from diverse ecological niches, a new lipopeptide biosurfactant was identified from a marine bacterium; Aneurinibacillus aneurinilyticus strain SBP-11, which was isolated from a marine diversity hotspot, Gulf of Mannar, India. A new lipopeptide biosurfactant was purified and characterized based on TLC, FT-IR, NMR, GC-MS, HPLC, MALDI-TOF-MS and tandem MS analysis as Stearic acid-Thr-Tyr-Val-Ser-Tyr-Thr (named as Aneurinifactin). The critical micelle concentration of Aneurinifactin was 26mgL^-1 at a surface tension of 26mNm^-1. Further, the biosurfactant showed stable emulsification at a wide range of pH (2-9) and temperature up to 80°C. Aneurinifactin showed promising antimicrobial activity and concentration dependent efficient oil recovery. This is the first report on Aneurinifactin, a lipopeptide biosurfactant produced by a marine A. aneurinilyticus SBP-11, which could be explored as a promising candidate for use in various biomedical and industrial applications.