Isolation, characterization, and application of biosurfactant by Klebsiella pneumoniae strain IVN51 isolated from hydrocarbon-polluted soil in Ogoniland, Nigeria

An Insightful Overview of Microbial Biosurfactant: A Promising Next-Generation Biomolecule for Sustainable Future

Microbial biosurfactant is an emerging vital biomolecule of the 21st century. They are amphiphilic compounds produced by microorganisms and possess unique properties to reduce surface tension activity. The use of microbial surfactants spans most of the industrial fields due to their biodegradability, less toxicity, being environmentally safe, and being synthesized from renewable sources. These would be highly efficient eco-friendly alternatives to petroleum-derived surfactants that would open up new approaches to research on the production of biosurfactants. In the upcoming era, biobased surfactants will become a dominating multifunctional compound in the world market. Research on biosurfactants ranges from the search for novel microorganisms that can produce new molecules, structural and physiochemical characterization of biosurfactants, and fermentation process for enhanced large-scale productivity and green applications. The main goal of this review is to provide an overview of the recent state of knowledge and trends about microbially derived surfactants, various aspects of biosurfactant production, definition, properties, characteristics, diverse advances, and applications. This would lead a long way in the production of biosurfactants as globally successful biomolecules of the current century.

Production and characterization of rhamnolipid biosurfactant from thermophilic Geobacillus stearothermophilus bacterium isolated from Uhud mountain

Introduction

Biosurfactants have been given considerable attention as they are potential candidates for several biotechnological applications.

Materials and methods

In this study, a promising thermophilic biosurfactant-producing HA-2 was isolated from the volcanic and arid region of Uhud mountain, Madinah, Saudi Arabia. It was identified using 16S rRNA gene sequence analysis. The biosurfactant production ability was screened using different methods such as the drop collapse test, oil spreading test, hemolytic activity test, CTAB test, and emulsification index. The ability of rhamnolipid production by the tested strain was confirmed by the polymerase chain reaction (PCR) of rhlAB. The affinity of thermophilic HA-2 to hydrophobic substrates was also investigated. Optimization of biosurfactant production was conducted. The biological activities of produced surfactant were investigated.

Results and discussion

The isolated HA-1 was identified as Geobacillus stearothermophilus strain OR911984. It could utilize waste sunflower frying oil (WSFF) oil as a low-cost carbon source. It showed high emulsification activity (52 ± 0.0%) and positive results toward other biosurfactant screening tests. The strain showed high cell adhesion to hexane with 41.2% cell surface hydrophobicity. Fourier-transform infrared (FTIR) spectra indicated the presence of hydrophobic chains that comprise lipids, sugars, and hydrophilic glycolipid components. The optimization results showed the optimal factors included potato peel as a carbon source with 68.8% emulsification activity, yeast extract as a nitrogen source with 60% emulsification activity, a pH of 9 (56.6%), and a temperature of 50° (72%). The kinetics showed that optimum biosurfactant production (572.4 mg/L) was recorded at 5 days of incubation. The produced rhamnolipid biosurfactant showed high antimicrobial activity against some human and plant pathogenic bacterial and fungal isolates and high antioxidant activity (90.4%). In addition, it enhanced wheat (Triticum aestivum) growth, with the greatest enhancement obtained with the 5% concentration. Therefore, thermophilic G. stearothermophilus is a promising rhamnolipid biosurfactant producer that utilizes many organic wastes. The produced biosurfactant could be applied as a promising emulsifier, antimicrobial, antioxidant, and plant growth promoter.

Production of biosurfactant by salt-resistant Bacillus in lead-supplemented media: application and toxicity

A group of biosurfactants are lipopeptides that are produced by some microorganisms, especially Bacillus strains. They are new bioactive agents with anticancer, antibacterial, antifungal, and antiviral activities. Also, they are used in sanitation industries. In this study, a lead-resistant strain of Bacillus halotolerans was isolated for lipopeptide production. This isolate exhibited metal resistance (lead, calcium, chromium, nickel, copper, manganese, and mercury), salt tolerance (12%), and antimicrobial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Saccharomyces cerevisiae. The production of lipopeptide was optimized, concentrated, and then extracted from the polyacrylamide gel in a simple way for the first time. The nature of the purified lipopeptide was determined by FTIR, GC/MS, and HPLC analyses. The purified lipopeptide indicated significant antioxidant properties (90.38% at a concentration of 0.8 mg ml-1). Also, it had anticancer activity by apoptosis (flow cytometry analysis) in MCF-7 cells, while it had no cytotoxicity on HEK-293 normal cells. Therefore, Bacillus halotolerans lipopeptide has the potential to be used as an antioxidant, antimicrobial, or anticancer agent in the medical and food industries.

Isolation, identification, and screening of biosurfactant-producing and hydrocarbon-degrading bacteria from oil and gas industrial waste

Qatar is one of the biggest oil and gas producers in the world, coupled with it is challenging environmental conditions (high average temperature: >40 °C, low annual rainfall: 46.71 mm, and high annual evaporation rate: 2200 mm) harbors diverse microbial communities that are novel and robust, with the potential to biodegrade hydrocarbons. In this study, we collected hydrocarbon contaminated sludge, wastewater and soil samples from oil and gas industries in Qatar. Twenty-six bacterial strains were isolated in the laboratory from these samples using high saline conditions and crude oil as the sole carbon source. A total of 15 different bacterial genera were identified in our study that have not been widely reported in the literature or studied for their usage in the biodegradation of hydrocarbons. Interestingly, some of the bacteria that were identified belonged to the same genus however, demonstrated variable growth rates and biosurfactant production. This indicates the possibility of niche specialization and specific evolution to acquire competitive traits for better survival. The most potent strain EXS14, identified as Marinobacter sp., showed the highest growth rate in the oil-containing medium as well as the highest biosurfactant production. When this strain was further tested for biodegradation of hydrocarbons, the results showed that it was able to degrade 90 to 100% of low and medium molecular weight hydrocarbons and 60 to 80% of high molecular weight (C35 to C50) hydrocarbons. This study offers many promising leads for future studies of microbial species and their application for the treatment of hydrocarbon contaminated wastewater and soil in the region and in other areas with similar environmental conditions.

Physics of self-assembly and morpho-topological changes of Klebsiella pneumoniae in desiccating sessile droplets

HYPOTHESIS

The bacteria suspended in pure water self-assemble into unique patterns depending on bacteria-bacteria, bacteria-substrate and bacteria-liquid interactions. The physical forces acting on bacteria vary based on their respective spatial location inside the droplet cause an assorted magnitude of physical stress. The shear and dehydration induced stress on pathogens(bacteria) in drying bio-fluid droplets alters the viability and infectivity.

EXPERIMENTS

We have investigated the flow and desiccation-driven self-assembly of Klebsiella pneumoniae in the naturally evaporating sessile droplets. Klebsiella pneumoniae exhibits extensive changes in its morphology and forms unique patterns as the droplet dries, revealing hitherto unexplored rich physics governing its survival and infection strategies. Self-assembly of bacteria at the droplet contact line is characterized by order-to-disorder packing transitions with high packing densities and excessive deformations (analysed using scanning electron microscopy and atomic force microscopy). In contrast, thin-film instability-led hole formation at the center of the droplet engenders spatial packing of bacteria analogous to honeycomb weathering.

FINDINGS

Self-assembly favors the bacteria at the rim of the droplet, leading to enhanced viability and pathogenesis on the famously known "coffee ring" of the droplet compared to the bacteria present at the center of the droplet residue. Mechanistic insights gained via our study can have far-reaching implications for bacterial infection through droplets, e.g., through open wounds.

Production, Characterization, and Application of Biosurfactant From Lactobacillus plantarum OG8 Isolated From Fermenting Maize (Zea Mays) Slurry

Biosurfactants have wide applications in several industries. However, high production costs and safety concerns have limited their comprehensive use. Twenty-five strains of lactic acid bacteria, isolated from fermenting maize slurry, were screened for biosurfactant production using the emulsification activity (E24) assay. The selected bacterium was identified molecularly using the 16S rRNA gene sequencing as Lactobacillus plantarum OG8. The effect of some cultural factors on biosurfactant production from the bacterium, using pineapple peel as a low-cost substrate, was investigated. The optimum yield of biosurfactant occurred at a 48 h incubation period, using glucose and peptone as carbon and nitrogen sources, respectively. The biosurfactant was characterized to possess mostly carbohydrates, followed by protein and lipid contents. Optima pH 10.0 and temperature 60 °C were the best for the biosurfactant activity. The biosurfactant exhibited antimicrobial activity against bacterial pathogens Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumoniae, at a concentration of 5.0 mg/mL. The use of pineapple peel as a low-cost substrate for biosurfactant production from Lactobacillus plantarum OG8 will serve for cost-effective production. The biosurfactantt produced exhibited promising properties such as thermostability and antimicrobial activity against food spoilage and pathogenes that could make it suitable for food processing and preservation.

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 production prospects of a Gram-negative bacterium-Klebsiella pneumoniae ssp. ozaenae BK34

Increasing environmental concerns have brought natural surfactant produced by microorganisms into limelight due to their lesser toxicity, biodegradable nature, and retention of activity at extreme conditions. In the present investigation, the surfactant production perspective of capsulated Gram-negative bacilli Klebsiella pneumoniae ssp. ozaenae BK34 was explored. It was identified on the basis of PCR amplification of conserved region of 16SrRNA using species specific primers. Highest oil displacement and emulsification (E₂₄) index of 6.8 cm and 20% along with 4.38-fold increase in biomass were attained using olive oil (2% (v/v)) as substrate. Incorporation of urea at 0.5% (w/v) concentration increased the oil displacement, E₂₄ index, and drop diameter to 9.2 cm, 77.50%, and 0.80 cm, respectively, accompanied by 5.38-fold increase in biomass production. Biosurfactant level was recorded maximum at 30 °C as apparent from the oil displacement of 9.3 cm and E₂₄ index of 75%. Reduction in incubation temperature to 25 °C abated oil displacement (5.2 cm) and E₂₄ index (17.66%). Biosurfactant production was also appeared to be pH sensitive as shifting pH from 7.0 to 6.0 or 8.0 reduced the E₂₄ index from 75 to 35% and 25%, respectively. Inoculum of stationary phase bacterial biomass at the proportion of 0.05% (w/v) was found adequate in triggering maximum biosurfactant production while the log phase biomass delayed the production significantly. Acid precipitation method was able to yield 7 g/L biosurfactant at pH 2. The surfactant was allocated to glycolipopeptide class on the basis of FTIR spectroscopy.

Looking through the FOG: microbiome characterization and lipolytic bacteria isolation from a fatberg site

Sewer systems are complex physical, chemical and microbial ecosystems where fats, oils and grease (FOG) present a major problem for sewer management. Their accumulation can lead to blockages (‘Fatbergs’), sewer overflows and disruption of downstream wastewater treatment. Further advancements of biological FOG treatments need to be tailored to degrade the FOG, and operate successfully within the sewer environment. In this study we developed a pipeline for isolation of lipolytic strains directly from two FOG blockage sites in the UK, and isolated a range of highly lipolytic bacteria. We selected the five most lipolytic strains using Rhodamine B agar plates and pNP-Fatty acid substrates, with two Serratia spp., two Klebsiella spp. and an environmental Acinetobacter strain that all have the capacity to grow on FOG-based carbon sources. Their genome sequences identified the genetic capacity for fatty acid harvesting (lipases), catabolism and utilization (Fad genes). Furthermore, we performed a preliminary molecular characterization of the microbial community at these sites, showing a diverse community of environmental bacteria at each site, but which did include evidence of sequences related to our isolates. This study provides proof of concept to isolation strategies targeting Fatberg sites to yield candidate strains with bioremediation potential for FOG in the wastewater network. Our work sets the foundation for development of novel bioadditions tailored to the environment with non-pathogenic Acinetobacter identified as a candidate for this purpose.

Production optimization, stability and oil emulsifying potential of biosurfactants from selected bacteria isolated from oil-contaminated sites

Oil pollution is of increasing concern for environmental safety and the use of microbial surfactants in oil remediation has become inevitable for their efficacy and ecofriendly nature. In this work, biosurfactants of bacteria isolated from oil-contaminated soil have been characterized. Four potent biosurfactant-producing strains (SD4, SD11, SD12 and SD13) were selected from 27 isolates based on drop collapse assay and emulsification index, and identified as species belonging to Bacillus, Burkholderia, Providencia and Klebsiella, revealed from their 16S rRNA gene-based analysis. Detailed morphological and biochemical characteristics of each selected isolate were determined. Their growth conditions for maximum biosurfactant production were optimized and found quite similar among the four isolates with a pH of 3.0 and temperature 37°C after 6 or 7 days of growth on kerosene. The biosurfactants of SD4, SD11 and SD12 appeared to be glycolipids and that of SD13 a lipopeptide. Emulsification activity of most of the biosurfactants was stable at low and high temperatures (4-100°C), a wide range of pH (2-10) and salt concentrations (2-7% NaCl). Each biosurfactant showed antimicrobial activity against two or more pathogenic bacteria. The biosurfactants were well-capable of emulsifying kerosene, diesel and soya bean, and could efficiently degrade diesel.

Biosurfactant is a powerful tool for the bioremediation of heavy metals from contaminated soils

Heavy metal toxicity has become a pressing ecological problem that affects the ecosystems through bioaccumulation, representing a serious public health hazard. Many conventional strategies have been developed and applied to decontaminate and restore metal-contaminated areas. However, these conventional approaches are not very suitable and environmentally safe for heavy metal remediation because of their high operational costs, high energy requirements, post-waste disposal problems, and secondary pollutant generation. Thus, biosurfactant-based bioremediation of heavy metals is a sustainable and promising approach because of its biodegradation capability, economic effectiveness, and ecofriendly nature. Pseudomonas sp., Bacillus sp., Citrobacter freundii, and Candida tropicalis have been isolated as potential sources of biosurfactants and produce compounds such as surfactin, rhamnolipids, and sophorolipids. Owing to the severity of heavy metal pollution in certain parts of the environment, biosurfactants have garnered great interest and attention as an emerging multi-functional technology of the new century for successful removal of heavy metal pollutants. The present study describes the role of biosurfactants in the bioremediation of heavy metals from contaminated environments. Moreover, the interaction mechanism underlying biosurfactant-metal complexation and metal remediation are discussed. Based on the review of the literature, further research is warranted to elucidate the mechanistic roles and explore the structural characterization and gene regulation of biosurfactants to improve their productivity and expand their applicability in bioremediation.

Isolation, screening and molecular characterization of biosurfactant producing bacteria from soil samples of auto repair shops

A total of 107 bacterial strains were isolated from used motor oil contaminated soil samples from auto-repair shops. The isolates were evaluated for their biosurfactant production abilities by employing a series of screening techniques, including hemolytic assay, oil displacement assay, drop-collapse assay, and parafilm M test. The potential biosurfactant producers were characterized by 16S rDNA-based molecular tools and were identified as Proteus mirabilis, Klebsiella pneumoniae, Enterobacter cloacae, Micrococcus sp., Citrobacter sp., and Bacillus sp. The widest clearing zone with a diameter of 6.5 cm was observed upon the addition of cell-free supernatant (CFS) from P. mirabilis SLM-B52 as assayed by the oil displacement test. Remarkable emulsification indexes, equivalent to 42% (against kerosene), 53% (against xylenes), and 50% (against benzene and toluene), were recorded by the CFSs of Micrococcus sp. SLM-B28, P. mirabilis SLM-B85, and K. pneumoniae SLM-B46, respectively. Du Noüy tensiometer analysis showed that biosurfactant produced by P. mirabilis SLM-B52 has the highest surface tension reduction capacity with a value of 30.5 mN m^-1. The emulsifying activity of a CFS from P. mirabilis was also described in this study for the first time. Taking together, biosurfactants from promising bacterial strains have potential application in microorganism-based biodegradation processes of hydrocarbons which cause detrimental effects on the environment.

Decolorization and discovery of metabolic pathway for the degradation of Mordant Black 11 dye by Klebsiella sp. MB398

Extensive utilization of the synthetic dyes in various industries is leading to water and soil contamination and ultimately impacting the humans. A research study was conducted for investigating the biodecolorization and biotransformation of Mordant Black 11 dye. For this purpose, potential of biofilm forming bacteria Klebsiella pneumoniae MB398 isolated from effluent outlets of Tops Food Industry, Hattar, Pakistan, was assessed to decolorize and transform Mordant Black 11 dye. Bacterial strain MB398 exhibited the capability of growing optimally at acidic pH (pH 6.0). Klebsiella pneumoniae MB398 efficiently decolorized Mordant Black 11 dye (64.55%) in aerobic environment at pH 6.0 and 37 °C over 24 h, which further increased to 75.35% over a period of 72 h of incubation. Strain MB398 also exhibited the capability of decolorizing Mordant Black 11 dye in the presence of cadmium (63.71%), chromium (61.78%), and copper (61.50%), respectively. UV-VIS spectrophotometric analysis, FTIR, and HPLC spectra were also indicative of biotransformation of dye molecules by Klebsiella pneumoniae MB398. GC-MS analysis of Mordant Black 11 dye revealed formation of 9 novel and unique metabolites including phenol,2,4-bis(1,1-dimethylethyl); 9-eicosene, (E); ethanol,2,2-(2-propenyloxy); acetic acid, benzene; 1-naphthol; methyl formate; valeraldehyde,2,4-dimethyl; and 7-hexadecene (Z). A possible metabolic pathway depicting the biotransformation of Mordant Black 11 dye by Klebsiella pneumoniae MB398 was projected. Findings of the current research study strongly suggest application of Klebsiella pneumoniae MB398 for developing large scale bioremediation strategies for the abatement of synthetic dyes to retain environmental sustainability in bioeconomic way.

Production, functional stability, and effect of rhamnolipid biosurfactant from Klebsiella sp. on phenanthrene degradation in various medium systems

The present study investigated the stability and efficacy of a biosurfactant produced by Klebsiella sp. KOD36 under extreme conditions and its potential for enhancing the solubilization and degradation of phenanthrene in various environmental matrices. Klebsiella sp. KOD36 produced a mono-rhamnolipids biosurfactant with a low critical micelle concentration (CMC) value. The biosurfactant was stable under extreme conditions (60 °C, pH 10 and 10% salinity) and could lower surface tension by 30% and maintained an emulsification index of > 40%. The emulsion index was also higher (17-43%) in the presence of petroleum hydrocarbons compared to synthetic surfactant Triton X-100. Investigation on phenanthrene degradation in three different environmental matrices (aqueous, soil-slurry and soil) confirmed that the biosurfactant enhanced the solubilization and biodegradation of phenanthrene in all matrices. The high functional stability and performance of the biosurfactant under extreme conditions on phenanthrene degradation show the great potential of the biosurfactant for remediation applications under harsh environmental conditions.

Remarkable shift in structural and functional properties of an animal charcoal-polluted soil accentuated by inorganic nutrient amendment

Background

Soils polluted with animal charcoal from skin and hide cottage industries harbour extremely toxic and carcinogenic hydrocarbon pollutants and thus require a bio-based eco-friendly strategy for their depuration. The effects of carbon-free mineral medium (CFMM) amendment on hydrocarbon degradation and microbial community structure and function in an animal charcoal-polluted soil was monitored for 6 weeks in field moist microcosms consisting of CFMM-treated soil (FN4) and an untreated control (FN1). Hydrocarbon degradation was monitored using gas chromatography-flame ionization detector (GC-FID), and changes in microbial community structure were monitored using Kraken, while functional annotation of putative open reading frames (ORFs) was done using KEGG KofamKOALA and NCBI’s conserved domain database (CDD).

Results

Gas chromatographic analysis of hydrocarbon fractions revealed the removal of 84.02% and 82.38% aliphatic and 70.09% and 70.14% aromatic fractions in FN4 and FN1 microcosms in 42 days. Shotgun metagenomic analysis of the two metagenomes revealed a remarkable shift in the microbial community structure. In the FN4 metagenome, 92.97% of the population belong to the phylum Firmicutes and its dominant representative genera Anoxybacillus (64.58%), Bacillus (21.47%) and Solibacillus (2.39%). In untreated FN1 metagenome, the phyla Proteobacteria (56.12%), Actinobacteria (23.79%) and Firmicutes (11.20%), and the genera Xanthobacter (9.73%), Rhizobium (7.49%) and Corynebacterium (7.35%), were preponderant. Functional annotation of putative ORFs from the two metagenomes revealed the detection of degradation genes for aromatic hydrocarbons, benzoate, xylene, chlorocyclohexane/chlorobenzene, toluene and several others in FN1 metagenome. In the FN4 metagenome, only seven hydrocarbon degradation genes were detected.

Conclusion

This study revealed that though CFMM amendment slightly increases the rate of hydrocarbon degradation, it negatively impacts the structural and functional properties of the animal charcoal-polluted soil. It also revealed that intrinsic bioremediation of the polluted soil could be enhanced via addition of water and aeration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-020-00089-9.

Improved Biosurfactant Production by Enterobacter cloacae B14, Stability Studies, and its Antimicrobial Activity

This work aimed to optimize carbon and nitrogen sources for the growth of Enterobacter cloacae B14 and its biosurfactant (BS) production via One-Variable-At-a-Time (OVAT) method. The BS stability under a range of pH and temperatures was assessed. Antimicrobial activity against Gram-positive and Gram-negative pathogens was determined by the agar well diffusion method. The results showed that the optimum carbon and nitrogen sources for BS production were maltose and yeast extract, respectively, with a maximum BS yield of (39.8 ± 5.2) mg BS/g biomass. The highest emulsification activity (E24) was 79%, which is significantly higher than in the previous studies. We found that B14 BS can withstand a wide range of pH values from 2 to10. It could also function under a range of temperatures from 30-37°C. Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectrometry (FTIR) analysis confirmed that B14 BS is a glycolipid-like compound, which is rarely found in Enterobacter spp. Cell-free broth showed inhibition against various pathogens, preferable to Gram-positive ones. It had better antimicrobial activity against Bacillus subtilis than a commonly-used antibiotic, tetracycline. Furthermore, B14 broth could inhibit the growth of a tetracycline-resistant Serratia marcescens. Our results showed promising B14 BS applications not only for bioremediation but also for the production of antimicrobial products.

Characterization of Extracellular Biosurfactants Expressed by a Pseudomonas putida Strain Isolated from the Interior of Healthy Roots from Sida hermaphrodita Grown in a Heavy Metal Contaminated Soil

Pseudomonas putida E41 isolated from root interior of Sida hermaphrodita (grown on a field contaminated with heavy metals) showed high biosurfactant activity. In this paper, we describe data from mass spectrometry and genome analysis, to improve our understanding on the phenotypic properties of the strain. Supernatant derived from P. putida E41 liquid culture exhibited a strong decrease in the surface tension accompanied by the ability for emulsion stabilization. We identified extracellular lipopeptides, putisolvin I and II expression but did not detect rhamnolipids. Their presence was confirmed by matrix-assisted laser desorption and ionization (MALDI) TOF/TOF technique. Moreover, ten phospholipids (mainly phosphatidylethanolamines PE 33:1 and PE 32:1) which were excreted by vesicles were also detected. In contrast the bacterial cell pellet was dominated by phosphatidylglycerols (PGs), which were almost absent in the supernatant. It seems that the composition of extracellular (secreted to the environment) and cellular lipids in this strain differs. Long-read sequencing and complete genome reconstruction allowed the identification of a complete putisolvin biosynthesis pathway. In the genome of P. putida E41 were also found all genes involved in glycerophospholipid biosynthesis, and they are likely responsible for the production of detected phospholipids. Overall this is the first report describing the expression of extracellular lipopeptides (identified as putisolvins) and phospholipids by a P. putida strain, which might be explained by the need to adapt to the highly contaminated environment.

Isolation, characterization and antibacterial effect of biosurfactant from Candida parapsilosis

In the present study, a biosurfactant producing Candida parapsilosis strain was isolated and identified by our laboratory. Different biosurfactant screening tests such as drop collapse, oil spreading, emulsification index and hemolytic activity confirmed the production of biosurfactant by the isolated Candida parapsilosis strain. The biosurfactant showed significant emulsifying index, drop collapse and oil-spread activity. The partially purified biosurfactant was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Gas Chromatography-Mass Spectroscopy (GC-MS). The FT-IR results indicated phenol (O-H), amide (N-H) and carbon functional group peaks like C[bond, double bond]O and C[bond, double bond]C at their identified places. GC-MS analysis revealed the presence of 13-docosenamide type of compound with a molecular weight of 337.5 g mol^-1. The isolated biosurfactant showed significant antibacterial activity against pathogenic Escherichia coli and Staphylococcus aureus strains at the concentrations of 10 and 5 mg ml^-1 respectively. Growth inhibition of both Gram positive and Gram negative pathogenic strains designated the future prospect of exploring the isolated biosurfactant as broad spectrum antibacterial agent.