Enhanced healing of full-thickness burn wounds using di-rhamnolipid

Antibiofilm and wound healing efficacy of rhamnolipid biosurfactant against pathogenic bacterium Staphylococcus aureus

The present study evaluates the in-vitro antibiofilm activity against the biofilm formed by Staphylococcus aureus, and the wound-healing efficacy of two different types of rhamnolipids produced by Pseudomonas aeruginosa strain JS29 in S.aureus infected wounds. The biosurfactant production was carried out in a mineral salt medium supplemented with 2 % Glucose and 2 % Glycerol individually and thus were designated as RL-Glu and RL-Gly respectively. 0.5 mg/ml of RL-Glu and RL-Gly demonstrated 90 % growth inhibition of S. aureus while exhibiting bactericidal activity at 4 mg/ml of RL-Glu and 1 mg/ml of RL-Gly. Both types of rhamnolipid cause changes in membrane permeability leading to pathogens' non-viability. 90 % inhibition of biofilm formation by S. aureus was observed at 2 mg/ml of RL-Glu and 0.5 mg/ml of RL-Gly, while 0.5 mg/ml of both rhamnolipid disrupted 90 % of the preformed biofilm. 0.5 mg/ml of RL-Glu and RL-Gly decreases the production of exopolysaccharides and also causes structural alteration. 0.5 mg/ml of RL-Glu and RL-Gly were found to exhibit effective wound healing efficacy in S. aureus infected wounds within 7 days of treatment. Histopathological studies of wound sites revealed efficient wound management by both the rhamnolipid. LCMS and GCMS characterization of the biosurfactant revealed that JS29 produces different rhamnolipid congeners when grown on different carbon sources, thereby influencing the antimicrobial, antibiofilm, and wound healing efficacy of rhamnolipid.

Application of Biosurfactants in Medical Sciences

Biosurfactants derived from microorganisms have attracted widespread attention in scientific research due to their unique surface activity, low toxicity, biodegradability, antibacterial properties, and stability under extreme conditions. Biosurfactants are widely used in many fields, such as medicine, agriculture, and environmental protection. Therefore, this review aims to comprehensively review and analyze the various applications of biosurfactants in the medical field. The central roles of biosurfactants in crucial medical areas are explored, like drug delivery, induction of tumor cell differentiation or death, treating bacterial and viral effects, healing wounds, and immune regulation. Moreover, a new outlook is introduced on optimizing the capabilities of biosurfactants through modification and gene recombination for better use in medicine. The current research challenges and future research directions are described, aiming to provide valuable insights for continuous study of biosurfactants in medicine.

Rubropunctatin-silver composite nanoliposomes for eradicating Helicobacter pylori in vitro and in vivo

Helicobacter pylori (H. pylori) is a major factor in peptic ulcer disease and gastric cancer, and its infection rate is rising globally. The efficacy of traditional antibiotic treatment is less effective, mainly due to bacterial biofilms and the formation of antibiotic resistance. In addition, H. pylori colonizes the gastrointestinal epithelium covered by mucus layers, the drug must penetrate the double barrier of mucus layer and biofilm to reach the infection site and kill H. pylori. The ethanol injection method was used to synthesize nanoliposomes (EPI/R-AgNPs@RHL/PC) with a mixed lipid layer containing rhamnolipids (RHL) and phosphatidylcholine (PC) as a carrier, loaded with the urease inhibitor epiberberine (EPI) and the antimicrobial agent rubropunctatin silver nanoparticles (R-AgNPs). EPI/R-AgNPs@RHL/PC had the appropriate size, negative charge, and acid sensitivity to penetrate mucin-rich mucus layers and achieve acid-responsive drug release. In vitro experiments demonstrated that EPI/R-AgNPs@RHL/PC exhibited good antibacterial activity, effectively inhibited urease activity, removed the mature H. pylori biofilm, and inhibited biofilm regeneration. In vivo antibacterial tests showed that EPI/R-AgNPs@RHL/PC exhibited excellent activity in eradicating H. pylori and protecting the mucosa compared to the traditional clinical triple therapy, providing a new idea for the treatment of H. pylori infection.

Innovative Wound Healing Hydrogel Containing Chicken Feather Keratin and Soy Isoflavone Genistein: In Vivo Studies

The current study was performed to isolate keratin from chicken feathers with an intention to develop a keratin-genistein wound-healing hydrogel, along with its in vivo analysis. Pre-formulation aspects were analysed by using FTIR; SEM; HPTLC, while gel was characterized for gel strength, viscosity, spreadability, drug content, etc. Additionally, an in vivo study along with biochemical factors against pro-inflammatory factors and histopathological studies were conducted to determine possible wound-healing and anti-inflammatory effects. Pre-formulation studies revealed the presence of amide bonds with region of dense fibrous keratin and an internal porous network in extracted keratin, which corresponds with standard keratin. Evaluation of optimised keratin-genistein hydrogel indicated the development of neutral, non-sticky hydrogel which spread evenly on the skin. In vivo studies in rats indicate higher degrees of wound-healing in combined hydrogel (94.65%) for a duration of 14 days as compared to an individual hydrogel formulation with the development of the epidermis and excessive proliferation of fibrous connective tissue indicating wound repair. Furthermore, the hydrogel inhibited the overexpression of IL-6 gene along with other pro-inflammatory factors, indicating its anti-inflammatory effects. In order to find out the possibility of closure of wounds and anti-inflammatory properties of the novel product, an in vivo investigation into the healing of wounds in laboratory animals was carried out through biochemical (ELISA and qRT-PCR) analyses against inflammatory markers (IL-2, IL-6, IL-1, IL-10, and COX-2) and histopathological (liver, skin, and the kidneys) investigations. Based on the results, we conclude that keratin-genistein hydrogel is a promising therapeutic molecule for the management of wound repair.

Wound healing efficacy of rhamnolipid-coated zinc oxide nanoparticle along with its in vivo antibacterial efficacy against Staphylococcus aureus

Rhamnolipids are microbial metabolites with antibacterial efficacies, which can be further boosted through the application of nanobiotechnology. In this study, the efficacy of rhamnolipid-coated zinc oxide nanoparticles (ZnRL) has been studied for their wound healing efficacy as well as in vivo antibacterial efficacy. Thus, this study evaluates the efficacy of ZnRL to heal an excised infected wound, which was compared with the healing efficacy of rhamnolipid and clindamycin. The study revealed that rhamnolipid-coated zinc oxide nanoparticles possess promising wound healing efficacy with prominent antibacterial activity in the rat model. Prominent wound healing in a Staphylococcus aureus infected excised wound was observed on the 5th day of the treatment when the wound site was treated with 100 μl of 0.5 mg/ml of ZnRL. This concentration of ZnRL was found to exhibit efficient antibacterial activity against the pathogen, thereby decreasing the amount of pathogen in the wound site. ZnRL exhibited efficient wound contraction, thereby decreasing the size of the wound prominently in 5 days. Histological study revealed efficient tissue remodelling in ZnRL-treated skin which resulted in rapid formation of the epidermis and recruitment of various dermal cells within the 5th day of treatment. The study also revealed the non-cytotoxic effect of the nanoparticles in fibroblast cell line L929 and the non-haemolytic effect against blood cells, indicating its potential in pharmaceuticals.

Microbial Biosurfactant as an Alternate to Chemical Surfactants for Application in Cosmetics Industries in Personal and Skin Care Products: A Critical Review

Cosmetics and personal care items are used worldwide and administered straight to the skin. The hazardous nature of the chemical surfactant utilized in the production of cosmetics has caused alarm on a global scale. Therefore, bacterial biosurfactants (BS) are becoming increasingly popular in industrial product production as a biocompatible, low-toxic alternative surfactant. Chemical surfactants can induce allergic responses and skin irritations; thus, they should be replaced with less harmful substances for skin health. The cosmetic industry seeks novel biological alternatives to replace chemical compounds and improve product qualities. Most of these chemicals have a biological origin and can be obtained from plant, bacterial, fungal, and algal sources. Various biological molecules have intriguing capabilities, such as biosurfactants, vitamins, antioxidants, pigments, enzymes, and peptides. These are safe, biodegradable, and environmentally friendly than chemical options. Plant-based biosurfactants, such as saponins, offer numerous advantages over synthetic surfactants, i.e., biodegradable, nontoxic, and environmentally friendly nature. Saponins are a promising source of natural biosurfactants for various industrial and academic applications. However, microbial glycolipids and lipopeptides have been used in biotechnology and cosmetics due to their multifunctional character, including detergency, emulsifying, foaming, and skin moisturizing capabilities. In addition, some of them have the potential to be used as antibacterial agents. In this review, we like to enlighten the application of microbial biosurfactants for replacing chemical surfactants in existing cosmetic and personal skincare pharmaceutical formulations due to their antibacterial, skin surface moisturizing, and low toxicity characteristics.

The Therapeutic Application of Tamarix aphylla Extract Loaded Nanoemulsion Cream for Acid-Burn Wound Healing and Skin Regeneration

Background and Objectives: Nanomedicine is a constantly growing field for the diagnosis and treatment of various diseases as well as for regenerative therapy. Nanotechnology-based drug-delivery systems improve pharmacological and pharmacokinetic profiles of plants based biologically active molecules. Based on traditional claims, leaves of the Tamarix aphylla (TA) were investigated for their potential healing activity on burn wounds. Materials and Methods: In this study, TA-based nanoemulsion was prepared. The nanoemulsion was characterized for size, zeta potential, pH, viscosity, and stability. The nanoemulsion containing plant extract was converted into cream and evaluated for its efficacy against acid-burn wounds inflicted in the dorsum of rabbits. The animals were classified into four main groups: Group A as a normal control group, Group B as a positive control (treated with cream base + silver sulfadiazine), Group C as a standard drug (silver sulfadiazine), and Group D as a tested (treated with nanoemulsion cream containing TA extract). The prepared system could deliver TA to the target site and was able to produce pharmacological effects. On days 0, 7, 14, 21, 28, and 35, wound contraction rate was used to determine healing efficacy. The wound samples were collected from the skin for histological examination. Results: Based on statistical analysis using wound-healing time, Group D showed a shorter period (21.60 ± 0.5098) (p < 0.01) than the average healing time of Group C (27.40 ± 0.6002) (p < 0.05) and Group B (33.40 ± 0.8126) (p < 0.05). The histopathological assessment showed that burn healing was better in Group D compared with Group C and Group B. The nanoemulsion cream had a non-sticky texture, low viscosity, excellent skin sensations, and a porous structure. By forming a protective layer on the skin and improving moisture, it enhanced the condition of burnt skin. Conclusions: According to the findings of this study, nanoemulsion cream containing TA extract has great potential in healing acid-burn wounds

Lipase-Mediated Mechanoenzymatic Synthesis of Sugar Esters in Dissolved Unconventional and Neat Reaction Systems

Mechanochemical and biocatalytic approaches in modern research are two major assets to develop greener processes. In the present study, these modular tools of sustainability are pointed toward the production of versatile and daily employed compounds such as surfactants. Toward this aim, glycolipids, a class of nonionic surfactants composed of ubiquitous and primary metabolites such as sugar and fatty acid moieties, represent a promising alternative to petroleum-derived surface-active agents. Therefore, the combination of biocatalysis with mechanochemistry aiming at glycolipid synthesis seemed a logical step that was taken in this study for the first time. The monoacylated model compound glucose-6-O-decanoate was synthesized with the help of a bead mill apparatus using two different unconventional dissolved reaction systems, namely, menthol-based hydrophobic deep eutectic solvents and 2-methyl-2-butanol, thus reaching up to 12% yield in the latter based on the conversion of vinyl decanoate, after only 90 min of reaction. In addition, a neat reaction system using an excess of vinylated fatty ester as an adjuvant allowed a 27 mM/h space-time yield. The overall significant increase in productivities, up to 6 times, compared to standard heating and shaking methods, shows the tremendous potential of mechanoenzymatic synthesis.

Rhamnolipid Nano-Micelles versus Alcohol-Based Hand Sanitizer: A Comparative Study for Antibacterial Activity against Hospital-Acquired Infections and Toxicity Concerns

Hospital-acquired infections (HAIs) are considered to be a major global healthcare challenge, in large part because of the development of microbial resistance to currently approved antimicrobial drugs. HAIs are frequently preventable through infection prevention and control measures, with hand hygiene as a key activity. Improving hand hygiene was reported to reduce the transmission of healthcare-associated pathogens and HAIs. Alcohol-based hand sanitizers are commonly used due to their rapid action and broad spectrum of microbicidal activity, offering protection against bacteria and viruses. However, their frequent administration has been reported to be associated with many side effects, such as skin sensitivity, skin drying, and cracks, which promote further skin infections. Thus, there is an essential need to find alternative approaches to hand sanitation. Rhamnolipids are glycolipids produced by Pseudomonas aeruginosa, and were shown to have broad antimicrobial activity as biosurfactants. We have previously demonstrated the antimicrobial activity of rhamnolipid nano-micelles against selected drug-resistant Gram-negative (Salmonella Montevideo and Salmonella Typhimurium) and Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae). To the best of our knowledge, the antimicrobial activity of rhamnolipid nano-micelles in comparison to alcohol-based hand sanitizers against microorganisms commonly causing HAIs in Egypt—such as Acinetobacter baumannii and Staphylococcus aureus—has not yet been studied. In the present work, a comparative study of the antibacterial activity of rhamnolipid nano-micelles versus alcohol-based hand sanitizers was performed, and their safety profiles were also assessed. It was demonstrated that rhamnolipid nano-micelles had a comparable antibacterial activity to alcohol-based hand sanitizer, with a better safety profile, i.e., rhamnolipid nano-micelles are unlikely to cause any harmful effects on the skin. Thus, rhamnolipid nano-micelles could be recommended to replace alcohol-based hand sanitizers; however, they must still be tested by healthcare workers in healthcare settings to ascertain their antimicrobial activity and safety.

Carbohydrate-carbohydrate interaction drives the preferential insertion of dirhamnolipid into glycosphingolipid enriched membranes

Rhamnolipids (RLs) are among the most important biosurfactants produced by microorganisms, and have been widely investigated because of their multiple biological activities. Their action appears to depend on their structural interference with lipid membranes, therefore several studies have been performed to investigate this aspect. We studied by X-ray scattering, neutron reflectometry and molecular dynamic simulations the insertion of dirhamnolipid (diRL), the most abundant RL, in model cellular membranes made of phospholipids and glycosphingolipids. In our model systems the affinity of diRL to the membrane is highly promoted by the presence of the glycosphingolipids and molecular dynamics simulations unveil that this evidence is related to sugar-sugar attractive interactions at the membrane surface. Our results improve the understanding of the plethora of activities associated with RLs, also opening new perspectives in their selective use for pharmaceutical and cosmetics formulations. Additionally, they shed light on the still debated role of carbohydrate-carbohydrate interactions as driving force for molecular contacts at membrane surface.

Bio-Evaluation of the Wound Healing Activity of Artemisia judaica L. as Part of the Plant’s Use in Traditional Medicine; Phytochemical, Antioxidant, Anti-Inflammatory, and Antibiofilm Properties of the Plant’s Essential Oils

Artemisia judaica (ArJ) is a Mediterranean aromatic plant used traditionally to treat gastrointestinal ailments, skin diseases, atherosclerosis, and as an immuno-stimulant. This study describes ArJ essential oil constituents and investigates their wound healing activity. The in vitro antioxidant and antibiofilm activities of ArJ essential oil were investigated. The in vivo pro/anti-inflammatory and oxidative/antioxidant markers were compared with standard silver sulfadiazine (SS) in a second-degree skin burn experimental rat model. The gas chromatography-equipped flame ionization detector (GC-FID) analysis of ArJ essential oil revealed the major classes of compounds as oxygenated monoterpenes (>57%) and cinnamic acid derivatives (18.03%). The antimicrobial tests of ArJ essential oil revealed that Bacillus cereus, Candida albicans, and Aspergillus niger were the most susceptible test organisms. Two second-degree burns (each 1 inch square in diameter) were created on the dorsum of rats using an aluminum cylinder heated to 120 °C for 10 s. The wounds were treated either with ArJ or SS ointments for 21 days, while the negative control remained untreated, and biopsies were obtained for histological and biochemical analysis. The ArJ group demonstrated a significant increase in antioxidant superoxide dismutase (SOD) and catalase (CAT) enzymatic activities, while lipid peroxide (LP) levels remained insignificant compared to the negative control group. Additionally, ArJ and SS groups demonstrated a significant decrease in inflammatory levels of tumor necrosis factor α (TNF-α) compared to the negative group, while interleukin 1 beta (IL-1b) and IL-6 were comparable to the negative group. At the same time, anti-inflammatory IL-10 and transforming growth factor beta 1 (TGF-b1) markers increased significantly in the ArJ group compared to the negative control. The ArJ results demonstrated potent wound healing effects, comparable to SS, attributable to antioxidant and anti-inflammatory effects as well as a high proportion of oxygenated monoterpenes and cinnamate derivatives.

Antiviral Activity of the Rhamnolipids Mixture from the Antarctic Bacterium Pseudomonas gessardii M15 against Herpes Simplex Viruses and Coronaviruses

Emerging and re-emerging viruses represent a serious threat to human health at a global level. In particular, enveloped viruses are one of the main causes of viral outbreaks, as recently demonstrated by SARS-CoV-2. An effective strategy to counteract these viruses could be to target the envelope by using surface-active compounds. Rhamnolipids (RLs) are microbial biosurfactants displaying a wide range of bioactivities, such as antibacterial, antifungal and antibiofilm, among others. Being of microbial origin, they are environmentally-friendly, biodegradable, and less toxic than synthetic surfactants. In this work, we explored the antiviral activity of the rhamnolipids mixture (M15RL) produced by the Antarctic bacteria Pseudomonas gessardii M15 against viruses belonging to Coronaviridae and Herpesviridae families. In addition, we investigated the rhamnolipids’ mode of action and the possibility of inactivating viruses on treated surfaces. Our results show complete inactivation of HSV-1 and HSV-2 by M15RLs at 6 µg/mL, and of HCoV-229E and SARS-CoV-2 at 25 and 50 µg/mL, respectively. Concerning activity against HCoV-OC43, 80% inhibition of cytopathic effect was recorded, while no activity against naked Poliovirus Type 1 (PV-1) was detectable, suggesting that the antiviral action is mainly directed towards the envelope. In conclusion, we report a significant activity of M15RL against enveloped viruses and demonstrated for the first time the antiviral effect of rhamnolipids against SARS-CoV-2.

Rhamnolipids from non-pathogenic Acinetobacter calcoaceticus: Bioreactor-scale production, characterization and wound healing potency

Rhamnolipids are predominantly produced from the opportunistic pathogen Pseudomonas aeruginosa, which restricts their scaled-up production and biomedical applications. Moreover, the wound healing property of rhamnolipids is mainly focused on either mono- or di-rhamnolipid congeners, which are obtained after extensive and costly purification procedures. Here, crude rhamnolipids from non-pathogenic Acinetobacter calcoaceticus BU-03 have been prepared and characterized and their wound healing potency evaluated in vitro and in vivo. Rhamnolipid extract was produced in a bioreactor by batch fermentation at a concentration of 12.7 ± 1.4 g/L. Characterization of the extract by Fourier Transform Infrared spectroscopy and mass spectrometry revealed characteristic rhamnolipid peaks. Rha-C10-C10 and Rha-Rha-C10-C10 appeared as the predominant congeners along with minor quantities of six more congeners. The rhamnolipid extract obtained from A. calcoaceticus had no toxicity against mouse fibroblast L929 cells and accelerated their migration. Transforming growth factor beta 1 (TGF-β1) has been shown to promote fibroblast migration by activating Smad3. It was found that the rhamnolipid extract enhanced Smad3 phosphorylation in L929 cells. In vivo studies showed that it promoted wound healing in mice with excisional wounds. The protein levels of TGF-β1 and alpha smooth muscle actin (α-SMA), a highly contractile protein, were significantly increased by 2.56- and 1.51-fold, respectively, in extract-treated compared with vehicle control-treated wounds, indicating that the activation of TGF-β1 signaling is possibly involved in the wound healing effect. These results suggest that a rhamnolipid extract obtained from A. calcoaceticus has potential as a wound healing material for topical application in cutaneous wound treatment.

In vivo wound-healing and antioxidant activity of aqueous extract of Roylea elegans leaves against physically induced burn model in Wistar albino rats

Roylea elegans Wall. ex Benth. is a lemon-scented hoary shrub belonging to the mint family (Lamiaceae). Traditionally, a local tribe of the Himalayan region uses leaves for scabs and skin infections. The aerial parts and leaves are widely used to cure various skin ailments. The plant is well known for two furanoid diterpenes, royeleganin and royelegafuran. The aqueous extract of Roylea elegans (AERE) leaves was investigated for wound-healing effects in rats using a physically induced burn model by assessing different parameters. Animals were divided into four groups (six rats in each group). Group I animals were considered as disease control and topically given base cream. Group II was considered as standard control and treated topically with Framycetin sulphate cream (1% w/w). Group III and IV animals were treated topically with creams containing 5 or 10% of AERE, respectively. Several parameters such as wound contraction rate, epithelialization period, and enzymatic and non-enzymatic antioxidant markers along with pro- and anti-inflammatory cytokines were studied followed by histopathological studies. The animals treated with AERE cream exhibited significant declination in the wound area and increased collagen content as compared to the disease control group. The results showed that the lower dose (5%) of AERE produced a significant decrease in the epithelialization period, wound contraction rate, and collagen content. Increased levels of cytokine production may be one of the mechanisms in accelerating the wound-healing process. The study established the traditional claim as an antioxidant and wound-healing potential of Roylea elegans by promoting the accelerated wound-healing activity against the physically induced burn model.

Recent Advances in Biomedical, Therapeutic and Pharmaceutical Applications of Microbial Surfactants

The spread of antimicrobial-resistant pathogens typically existing in biofilm formation and the recent COVID-19 pandemic, although unrelated phenomena, have demonstrated the urgent need for methods to combat such increasing threats. New avenues of research for natural molecules with desirable properties to alleviate this situation have, therefore, been expanding. Biosurfactants comprise a group of unique and varied amphiphilic molecules of microbial origin capable of interacting with lipidic membranes/components of microorganisms and altering their physicochemical properties. These features have encouraged closer investigations of these microbial metabolites as new pharmaceutics with potential applications in clinical, hygiene and therapeutic fields. Mounting evidence has indicated that biosurfactants have antimicrobial, antibiofilm, antiviral, immunomodulatory and antiproliferative activities that are exploitable in new anticancer treatments and wound healing applications. Some biosurfactants have already been approved for use in clinical, food and environmental fields, while others are currently under investigation and development as antimicrobials or adjuvants to antibiotics for microbial suppression and biofilm eradication strategies. Moreover, due to the COVID-19 pandemic, biosurfactants are now being explored as an alternative to current products or procedures for effective cleaning and handwash formulations, antiviral plastic and fabric surface coating agents for shields and masks. In addition, biosurfactants have shown promise as drug delivery systems and in the medicinal relief of symptoms associated with SARS-CoV-2 acute respiratory distress syndrome.

Rhamnolipid the Glycolipid Biosurfactant: Emerging trends and promising strategies in the field of biotechnology and biomedicine

Rhamnolipids (RLs) are surface-active compounds and belong to the class of glycolipid biosurfactants, mainly produced from Pseudomonas aeruginosa. Due to their non-toxicity, high biodegradability, low surface tension and minimum inhibitory concentration values, they have gained attention in various sectors like food, healthcare, pharmaceutical and petrochemicals. The ecofriendly biological properties of rhamnolipids make them potent materials to be used in therapeutic applications. RLs are also known to induce apoptosis and thus, able to inhibit proliferation of cancer cells. RLs can also act as immunomodulators to regulate the humoral and cellular immune systems. Regarding their antimicrobial property, they lower the surface hydrophobicity, destruct the cytoplasmic membrane and lower the critical micelle concentration to kill the bacterial cells either alone or in combination with nisin possibly due to their role in modulating outer membrane protein. RLs are also involved in the synthesis of nanoparticles for in vivo drug delivery. In relation to economic benefits, the post-harvest decay of food can be decreased by RLs because they prevent the mycelium growth, spore germination of fungi and inhibit the emergence of biofilm formation on food. The present review focuses on the potential uses of RLs in cosmetic, pharmaceutical, food and health-care industries as the potent therapeutic agents.

Chlorovirus PBCV-1 protein A064R has three of the transferase activities necessary to synthesize its capsid protein N-linked glycans

Paramecium bursaria chlorella virus-1 (PBCV-1) is a large double-stranded DNA (dsDNA) virus that infects the unicellular green alga Chlorella variabilis NC64A. Unlike many other viruses, PBCV-1 encodes most, if not all, of the enzymes involved in the synthesis of the glycans attached to its major capsid protein. Importantly, these glycans differ from those reported from the three domains of life in terms of structure and asparagine location in the sequon of the protein. Previous data collected from 20 PBCV-1 spontaneous mutants (or antigenic variants) suggested that the a064r gene encodes a glycosyltransferase (GT) with three domains, each with a different function. Here, we demonstrate that: domain 1 is a β-l-rhamnosyltransferase; domain 2 is an α-l-rhamnosyltransferase resembling only bacterial proteins of unknown function, and domain 3 is a methyltransferase that methylates the C-2 hydroxyl group of the terminal α-l-rhamnose (Rha) unit. We also establish that methylation of the C-3 hydroxyl group of the terminal α-l-Rha is achieved by another virus-encoded protein A061L, which requires an O-2 methylated substrate. This study, thus, identifies two of the glycosyltransferase activities involved in the synthesis of the N-glycan of the viral major capsid protein in PBCV-1 and establishes that a single protein A064R possesses the three activities needed to synthetize the 2-OMe-α-l-Rha-(1→2)-β-l-Rha fragment. Remarkably, this fragment can be attached to any xylose unit.

Microbial Biosurfactants in Cosmetic and Personal Skincare Pharmaceutical Formulations

Cosmetic and personal care products are globally used and often applied directly on the human skin. According to a recent survey in Europe, the market value of cosmetic and personal care products in Western Europe reached about 84 billion euros in 2018 and are predicted to increase by approximately 6% by the end of 2020. With these significant sums of money spent annually on cosmetic and personal care products, along with chemical surfactants being the main ingredient in a number of their formulations, of which many have been reported to have the potential to cause detrimental effects such as allergic reactions and skin irritations to the human skin; hence, the need for the replacement of chemical surfactants with other compounds that would have less or no negative effects on skin health. Biosurfactants (surfactants of biological origin) have exhibited great potential such as lower toxicity, skin compatibility, protection and surface moisturizing effects which are key components for an effective skincare routine. This review discusses the antimicrobial, skin surface moisturizing and low toxicity properties of glycolipid and lipopeptide biosurfactants which could make them suitable substitutes for chemical surfactants in current cosmetic and personal skincare pharmaceutical formulations. Finally, we discuss some challenges and possible solutions for biosurfactant applications.

A novel approach for the production of green biosurfactant from Pseudomonas aeruginosa using renewable forest biomass

The rising demand for surfactants by the pharmaceuticals and cosmetic industries has generated vast amounts of petroleum-based synthetic surfactants, which are often toxic and non-degradable. Owing to their low toxicity, stability in extreme conditions, and biodegradability, biosurfactants could represent a sustainable alternative. The present study aimed to maximize the production of rhamnolipids (RL) from Pseudomonas aeruginosa by optimizing glucose concentration, temperature, and C/N and C/P ratios. After 96 h of cultivation at 37 °C, the final RL concentration was 4.18 ± 0.19 g/L with a final yield of 0.214 ± 0.010 g/g_glucose when pure glucose was used as a carbon source. At present, the main obstacle towards commercialization of RL production is economic sustainability, due to the high cost of downstream processes and media components. For this reason, a renewable source such as wood hydrolysates (from birch and spruce woodchips) was examined here as a possible source of glucose for RL production. Both hydrolysates proved to be adequate, resulting in 2.34 ± 0.17 and 2.31 ± 0.10 g/L of RL, respectively, and corresponding yields of 0.081 ± 0.006 and 0.089 ± 0.004 g/g_sugar after 96 h. These results demonstrate the potential of using renewable biomass for the production of biosurfactants and, to the best of our knowledge, they constitute the first report on the use of wood hydrolysates for RL production.

High Di-rhamnolipid Production Using Pseudomonas aeruginosa KT1115, Separation of Mono/Di-rhamnolipids, and Evaluation of Their Properties

Rhamnolipids (RLs) are important bioproducts that are regarded as promising biosurfactant for applications in oil exploitation, cosmetics, and food industry. In this study, the newly isolated Pseudomonas aeruginosa KT1115 showed high production of di-RLs. The highest yield of RLs by P. aeruginosa KT1115, reaching 44.39 g/L after 8 days of fermentation in a 5 L bioreactor, was obtained from rapeseed oil-nitrate medium after process optimization. Furthermore, we established a new separation process that achieved up to 91.82% RLs recovery with a purity of 89% and further obtained mono/di-rhamnolipids. Finally, ESI-MS analysis showed that the RLs produced by strain KT1115 have a high proportion of di-RLs (mono-RLs: di-RLs = 11.47: 88.53), which have a lower critical micelle-forming concentration (8 mN/m) and better emulsification ability with kerosene (52.1% EI₂₄) than mono-RLs (167 mN/m and 41.4% EI₂₄, respectively). These results demonstrated that P. aeruginosa KT1115 is a potential industrial producer of di-RLs, which have improved applicability and offer significant commercial benefits.

Antifungal and Antivirulence Activity of Vaginal Lactobacillus Spp. Products against Candida Vaginal Isolates

Candida yeasts are generally found in the vaginal microbiota; however, disruption of the balance maintained by host factors and microorganisms results in vulvovaginal candidiasis (VVC). This study evaluated the antagonistic activity of vaginal Lactobacillus spp. on Candida albicans to verify whether active compounds of Lactobacillus spp. had antifungal and antivirulence activity. The antagonism assay showed that 15 out of 20 Lactobacillus strains had an inhibitory effect on C. albicans. Biosurfactants displayed surface-tension-reducing activity, with the best value obtained for Lactobacillus gasseri 1. Lactobacillus rhamnosus ATCC 9595, Lactobacillus acidophilus ATCC 4356, and Lactobacillus paracasei 11 produced biosurfactants that decreased C. albicans adhesion and disrupted biofilm formation. The best results were obtained in the pre-incubation assay for L. gasseri 1 and L. paracasei 11. Overall, Lactobacillus strains showed significant anti-Candida activity, and their biosurfactants exhibited considerable anti-adhesion and antibiofilm activity against C. albicans. To be considered safe for use in vivo, the safety of biosurfactant (BS) should be investigated using cytotoxicity assays.

Carrier oils in dermatology

Wounds are a common medical infliction. With the increase in microbial resistance and a shift of interest towards complementary medicines, essential oils have been shown to be beneficial in suppressing microbial growth. However, in practice, essential oils are more often diluted into a base due to the risk of topical adverse effects, such as dermatitis. There is a lack of collated evidence-based information on toxicity and efficacy of carrier oils. The current information on the subject matter is restricted to generic, aroma-therapeutic books and pamphlets, based on anecdotal evidence rather than an experimental approach. Therefore, this review aimed at identifying the recommended carrier oils used in dermatology and thereafter collating the scientific evidence to support the use of carrier oils together with essential oils recommended for dermatological use. Aloe vera gel had multiple studies demonstrating the ability to enhance wound healing; however, several other carrier oils have been largely neglected. It was observed that the extracts for certain plant species had been used to justify the use of the carrier oils of the same plant species. This is an inaccurate cross assumption due to the difference in chemical composition and biological activities. Lastly, despite these carrier oils being recommended as a base for essential oils, very little data was found on the interactive profile of the carrier oil with the essential oil. This review provides a platform for further studies, especially if essential oils are to receive credence in the scientific field.

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.

Microbial biosurfactants: current trends and applications in agricultural and biomedical industries

Synthetic surfactants are becoming increasingly unpopular in many applications due to previously disregarded effects on biological systems and this has led to a new focus on replacing such products with biosurfactants that are biodegradable and produced from renewal resources. Microbially derived biosurfactants have been investigated in numerous studies in areas including: increasing feed digestibility in an agricultural context, improving seed protection and fertility, plant pathogen control, antimicrobial activity, antibiofilm activity, wound healing and dermatological care, improved oral cavity care, drug delivery systems and anticancer treatments. The development of the potential of biosurfactants has been hindered somewhat by the myriad of approaches taken in their investigations, the focus on pathogens as source species and the costs associated with large-scale production. Here, we focus on various microbial sources of biosurfactants and the current trends in terms of agricultural and biomedical applications.

Composite Biopolymer-Based Wafer Dressings Loaded with Microbial Biosurfactants for Potential Application in Chronic Wounds

In this study two bioactive polysaccharide polymers kappa-carrageenan (CARR) and sodium alginate (SA) incorporated with microbial biosurfactants (BSs) were formulated as medicated wafer dressings for potential application in chronic wounds. Wafers were loaded with BSs at concentrations of 0.1% and 0.2% rhamnolipids (RL) and 0.1% and 5% sophorolipids (SL) and were functionally characterized using scanning electron microscopy (SEM), texture analysis (mechanical strength and in vitro wound adhesion), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD) and exudate handling properties (pore analysis, swelling index, water absorption (Aw), equilibrium water content (EWC), evaporative water loss (EWL) and water vapor transmission rate (WVTR). The wafers were tactile and ductile in appearance with a hardness range of 2.7⁻4.1 N and can withstand normal stresses but are also flexible to prevent damage to newly formed skin tissues. Wafers were porous (SEM) with pore sizes ranging from 78.8 to 141 µm, and BSs were not visible on the wafer surface or pore walls. The BSs enhanced the porosity of the wafers with values above 98%, while the Aw and EWC ranged from 2699⁻3569% and 96.58⁻98.00%, respectively. The EWL ranged from 85 to 86% after 24 h while the WVTR ranged from 2702⁻3080 g/m² day-1. The compatibility of BSs within the CARR-SA matrix was confirmed by seven characteristic functional groups which were consistently transmitted in the ATR-FTIR spectra. These novel medicated dressing prototypes can potentially help to achieve more rapid wound healing.

Mode of action of poloxamer-based surfactants in wound care and efficacy on biofilms

Surfactants are widely used as detergents, emulsifiers, wetting agents, foaming agents, and dispersants in both the food and oil industry. Their use in a clinical setting is also common, particularly in wound care. Complicated or chronic wounds show clinical signs of delayed healing, persistent inflammation, and the production of non-viable tissue. These types of wounds also present challenges such as infection and potentially house antimicrobial-tolerant biofilms. The use of wound cleansers to aid cleaning and debridement of the wound is essential. A large proportion of skin and wound cleansers contain surfactants but there is only a small amount of data that shows the effectiveness of them in the enhancement of wound closure. This review paper aims to explore the available literature surrounding the use and mode of action of surfactants in wound healing, in particular Poloxamer 188 (Pluronic F-68) and Poloxamer 407 (Pluronic F-127), and also uncover the potential mechanisms behind the enhancement of wound healing and comparison to other surfactants used in wound care. Furthermore, the presence of a microbial biofilm in the wound is a significant factor in delayed wound healing. Therefore, the effect of clinically used surfactants on biofilms will be discussed, with emphasis on poloxamer-based surfactants.

Simple glycolipids of microbes: Chemistry, biological activity and metabolic engineering

Glycosylated lipids (GLs) are added-value lipid derivatives of great potential. Besides their interesting surface activities that qualify many of them to act as excellent ecological detergents, they have diverse biological activities with promising biomedical and cosmeceutical applications. Glycolipids, especially those of microbial origin, have interesting antimicrobial, anticancer, antiparasitic as well as immunomodulatory activities. Nonetheless, GLs are hardly accessing the market because of their high cost of production. We believe that experience of metabolic engineering (ME) of microbial lipids for biofuel production can now be harnessed towards a successful synthesis of microbial GLs for biomedical and other applications. This review presents chemical groups of bacterial and fungal GLs, their biological activities, their general biosynthetic pathways and an insight on ME strategies for their production.

Designer rhamnolipids by reduction of congener diversity: production and characterization

Background

Rhamnolipids are biosurfactants featuring surface-active properties that render them suitable for a broad range of industrial applications. These properties include their emulsification and foaming capacity, critical micelle concentration, and ability to lower surface tension. Further, aspects like biocompatibility and environmental friendliness are becoming increasingly important. Rhamnolipids are mainly produced by pathogenic bacteria like Pseudomonas aeruginosa. We previously designed and constructed a recombinant Pseudomonas putida KT2440, which synthesizes rhamnolipids by decoupling production from host-intrinsic regulations and cell growth.

Results

Here, the molecular structure of the rhamnolipids, i.e., different congeners produced by engineered P. putida are reported. Natural rhamnolipid producers can synthesize mono- and di-rhamnolipids, containing one or two rhamnose molecules, respectively. Of each type of rhamnolipid four main congeners are produced, deviating in the chain lengths of the β-hydroxy-fatty acids. The resulting eight main rhamnolipid congeners with variable numbers of hydrophobic/hydrophilic residues and their mixtures feature different physico-chemical properties that might lead to diverse applications. We engineered a microbial cell factory to specifically produce three different biosurfactant mixtures: a mixture of di- and mono-rhamnolipids, mono-rhamnolipids only, and hydroxyalkanoyloxy alkanoates, the precursors of rhamnolipid synthesis, consisting only of β-hydroxy-fatty acids. To support the possibility of second generation biosurfactant production with our engineered microbial cell factory, we demonstrate rhamnolipid production from sustainable carbon sources, including glycerol and xylose. A simple purification procedure resulted in biosurfactants with purities of up to 90%. Finally, through determination of properties specific for surface active compounds, we were able to show that the different mixtures indeed feature different physico-chemical characteristics.

Conclusions

The approach demonstrated here is a first step towards the production of designer biosurfactants, tailor-made for specific applications by purposely adjusting the congener composition of the mixtures. Not only were we able to genetically engineer our cell factory to produce specific biosurfactant mixtures, but we also showed that the products are suited for different applications. These designer biosurfactants can be produced as part of a biorefinery from second generation carbon sources such as xylose.

Electronic supplementary material

The online version of this article (10.1186/s12934-017-0838-y) contains supplementary material, which is available to authorized users.

Anti-biofilm Properties of Bacterial Di-Rhamnolipids and Their Semi-Synthetic Amide Derivatives

A new strain, namely Lysinibacillus sp. BV152.1 was isolated from the rhizosphere of ground ivy (Glechoma hederacea L.) producing metabolites with potent ability to inhibit biofilm formation of an important human pathogens Pseudomonas aeruginosa PAO1, Staphylococcus aureus, and Serratia marcescens. Structural characterization revealed di-rhamnolipids mixture containing rhamnose (Rha)-Rha-C10-C10, Rha-Rha-C8-C10, and Rha-Rha-C10-C12 in the ratio 7:2:1 as the active principle. Purified di-rhamnolipids, as well as commercially available di-rhamnolipids (Rha-Rha-C10-C10, 93%) were used as the substrate for the chemical derivatization for the first time, yielding three semi-synthetic amide derivatives, benzyl-, piperidine-, and morpholine. A comparative study of the anti-biofilm, antibacterial and cytotoxic properties revealed that di-Rha from Lysinibacillus sp. BV152.1 were more potent in biofilm inhibition, both cell adhesion and biofilm maturation, than commercial di-rhamnolipids inhibiting 50% of P. aeruginosa PAO1 biofilm formation at 50 μg mL^-1 and 75 μg mL^-1, respectively. None of the di-rhamnolipids exhibited antimicrobial properties at concentrations of up to 500 μg mL^-1. Amide derivatization improved inhibition of biofilm formation and dispersion activities of di-rhamnolipids from both sources, with morpholine derivative being the most active causing more than 80% biofilm inhibition at concentrations 100 μg mL^-1. Semi-synthetic amide derivatives showed increased antibacterial activity against S. aureus, and also showed higher cytotoxicity. Therefore, described di-rhamnolipids are potent anti-biofilm agents and the described approach can be seen as viable approach in reaching new rhamnolipid based derivatives with tailored biological properties.

Rhamnolipids as epithelial permeability enhancers for macromolecular therapeutics

The use of surfactants as drug permeability enhancers across epithelial barriers remains a challenge. Although many studies have been performed in this field using synthetic surfactants, the possibility of employing surfactants produced by bacteria (the so called biosurfactants") has not been completely explored. Among them, one of the most well characterized class of biosurfactants are rhamnolipids. The aim of the study was to investigate the effect of rhamnolipids on the epithelial permeability of fluorescein isothiocyanate-labelled dextrans 4kDa and 10kDa (named FD4 and FD10, respectively) as model for macromolecular drugs, across Caco-2 and Calu-3monolayers. These cell lines were selected as an in vitro model for the oral and respiratory administration of drugs. Before performing permeability studies, rhamnolipids mixture was analysed in terms of chemical composition and quantification through mass analysis and HPLC. Cytotoxicity and transepithelial electrical resistance (TEER) studies were also conducted using Caco-2 and Calu-3 cell lines. A dose-dependent effect of rhamnolipids on TEER and FD4 or FD10 permeability across both cell lines was observed at relatively safe concentrations. Overall, results suggest the possibility of using rhamnolipids as absorption enhancers for macromolecular drugs through a reversible tight junction opening (paracellular route), despite more investigations are required to confirm their mechanism of action in term of permeability.

Structural Properties of Nonionic Monorhamnolipid Aggregates in Water Studied by Classical Molecular Dynamics Simulations

Molecular dynamics simulations were carried out to investigate the structure and stabilizing factors of aggregates of the nonionic form of the most common congener of monorhamnolipids, α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10), in water. Aggregates of size ranging from 5 to 810 monomers were observed in the simulation forming spherical and ellipsoidal structures, a torus-like structure, and a unilamellar vesicle. The effects of the hydrophobic chain conformation and alignment in the aggregate, role of monomer···monomer and monomer···water H-bonds, and conformations of monomers in the aggregate were studied in detail. The unilamellar vesicle is highly stable due to the presence of isolated water molecules inside the core adding to the binding energy. Dissociation of a monomer from a larger micellar aggregate is relatively easy compared to that from smaller aggregates as seen from potential of mean force calculations. This analysis also shows that monomers are held more strongly in aggregates of Rha-C10-C10 than the widely used surfactant sodium dodecyl sulfate. Comparisons between the aggregation behavior of nonionic and anionic forms of Rha-C10-C10 are presented.

Adjuvant Antibiotic Activity of Acidic Sophorolipids with Potential for Facilitating Wound Healing

The sophorolipid class of biosurfactants is finding increasing use in personal care as well as pharmaceutical products and has the potential to disrupt biofilm formation and inhibit the growth of a variety of clinically relevant organisms. In order to investigate potential biomedical applications of sophorolipids derived from nonpathogenic organisms, we fractionated and purified glycolipid biosurfactant sophorolipids produced by the yeast Starmerella bombicola, which yielded nonacetylated acidic C_18:1 congeners that were essentially free from other contaminants (>95% purity). These acidic sophorolipids have antimicrobial activities against the nosocomial infective agents Enterococcus faecalis and Pseudomonas aeruginosa, with significant reductions in CFU at concentrations of as low as 5 mg ml^-1 In addition, the sophorolipid showed similar effects against the same two bacterial strains when combined with kanamycin or cefotaxime. As a potential use of these sophorolipids is as a component of topically applied creams for the treatment of wound infections, it is clear that they must have no demonstrable adverse effect on wound healing. To assess this, we evaluated mammalian cell toxicity in vitro using viability tests, which revealed no adverse effect on either endothelial or keratinocyte-derived cell lines with sophorolipid concentrations of < 0.5 mg ml^-1 In addition, in vivo experiments using a mouse skin wounding assay revealed that the time course of healing wounds was unaffected by the application of sophorolipid-containing creams, and histological examination of regenerated skin tissue confirmed that the healing process was similar to that observed for control animals, with no evidence of inflammation. These results are consistent with the suggestion that acidic sophorolipids can be used as a component of antimicrobial creams to reduce the risk of wound infection during healing.

Effects of rhamnolipids on microorganism characteristics and applications in composting: A review

Biosurfactant rhmnolipids have been applied in many fields, especially in environmental bioremediation. According to previous researches, many research groups have studied the influence of rhamnolipids on microorganism characteristics and/or its application in composting. In this review, the effects of rhamnolipids on the cell surface properties of microorganisms was discussed firstly, such as cell surface hydrophobicity (CSH), electrical, surface compounds, etc. Moreover, the deeper mechanisms were also discussed, such as the effects of rhamnolipids on the structural characteristics and functional characteristics of the cell membrane, and the effects of rhamnolipids on the related enzymes and genes. Additionally, the application of rhamnolipids in composting was discussed, which is an important way for pollutant biodegradation and resource reutilization. It is believed that rhamnolipids will play more and more important role in composting.

Rhamnolipids form drug-loaded nanoparticles for dermal drug delivery

Bacterial biosurfactants are nature's strategy to solubilize and ingest hydrophobic molecules and nutrients using a fully biodegradable transport system. Eight structurally defined rhamnolipids were selected and investigated as potential drug carrier systems. Depending on the molecular structures defining their packing parameters, the rhamnolipids were found to form spherical nanoparticles with precisely defined average sizes between 5 and 100nm, low polydispersity, and stability over a broad concentration range as revealed from dynamic light scattering and electron microscopy. As rhamnolipids were tolerated well by the human skin, rhamnolipid nanoparticles were considered for dermal drug delivery and thus loaded with hydrophobic drug molecules. Using the drug model, Nile red, dexamethasone, and tacrolimus nanoparticles charged with up to 30% drug loading (w/w) were obtained. Nanoparticles loaded with Nile red were investigated for dermal drug delivery in a Franz cell using human skin. Fluoresence microscopy of skin slices indicated the efficient penetration of the model drug into human skin, both into the stratum corneum and although to a lesser extent into the lower epidermis. Rhamnolipid nanocarriers were found to be non-toxic to primary human fibroblasts in a proliferation assay and thus are considered candidates for the dermal delivery of drugs.

Targeted killing of myofibroblasts by biosurfactant di-rhamnolipid suggests a therapy against scar formation

Pathological myofibroblasts are often involved in skin scarring via generating contractile force and over-expressing collagen fibers, but no compound has been found to inhibit the myofibroblasts without showing severe toxicity to surrounding physiological cells. Here we report that di-rhamnolipid, a biosurfactant secreted by Pseudomonas aeruginosa, showed potent effects on scar therapy via a unique mechanism of targeted killing the myofibroblasts. In cell culture, the fibroblasts-derived myofibroblasts were more sensitive to di-rhamnolipid toxicity than fibroblasts at a concentration-dependent manner, and could be completely inhibited of their specific functions including α-SMA expression and collagen secretion/contraction. The anti-fibrotic function of di-rhamnolipid was further verified in rabbit ear hypertrophic scar models by presenting the significant reduction of scar elevation index, type I collagen fibers and α-SMA expression. In this regard, di-rhamnolipid treatment could be suggested as a therapy against skin scarring.