A Truncated Form of SpoT,Including the ACT Domain,Inhibits the Production of Cyclic Lipopeptide Arthrofactin,and Is Associated with Moderate Elevation of Guanosine 3′,5′-Bispyrophosphate Level in Pseudomonas sp. MIS38

Arthrofactin is a biosurfactant produced by Pseudomonas sp. MIS38. We have reported that transposon insertion into spoT (spoT::Tn5) causes moderate accumulation of guanosine 3′,5′-bispyrophosphate (ppGpp) and abrogates arthrofactin production. To analyze the linkage of SpoT function and ablation of arthrofactin production, we examined the spoT::Tn5 mutation. The results showed that spoT::Tn5 is not a null mutation, but encodes separate segments of SpoT. Deletion of the 3′ region of spoT increased the level of arthrofactin production, suggesting that the C-terminal region of SpoT plays a suppressive role. We evaluated the expression of a distinct segment of SpoT. Forced expression of the C-terminal region that contains the ACT domain resulted in the accumulation of ppGpp and abrogated arthrofactin production. Expression of the C-terminal segment also reduced MIS38 swarming and resulted in extensive biofilm formation, which constitutes the phenocopy of the spoT::Tn5 mutant.     

A new lipopeptide biosurfactant produced by Arthrobacter sp. strain MIS38.

A biosurfactant termed arthrofactin produced by Arthrobacter species strain MIS38 was purified and chemically characterized as 3-hydroxydecanoyl-D-leucyl-D-asparagyl-D-threonyl-D- leucyl-D-leucyl-D-seryl-L-leucyl-D-seryl-L-isoleucyl-L-isoleucyl-L-as paragyl lactone. Surface activity of arthrofactin was examined, with surfactin as a control. Critical micelle concentration values of arthrofactin and surfactin were around 1.0 x 10(-5) M and 7.0 x 10(-5) M at 25 degrees C, respectively. Arthrofactin was found to be five to seven times more effective than surfactin. The minimum surface tension value of arthrofactin was 24 mN/m at a concentration higher than the critical micelle concentration. According to the oil displacement assay, arthrofactin was a better oil remover than synthetic surfactants, such as Triton X-100 and sodium dodecyl sulfate. Arthrofactin is one of the most effective lipopeptide biosurfactants.     

Functional Analysis of A Pyoverdine Synthetase from Pseudomonas sp. MIS38

Fluorescent Pseudomonas sp. MIS38 produces a cyclic lipopeptide, arthrofactin. Arthrofactin is synthesized by a unique nonribosomal peptide synthetase (NRPS) with dual C/E-domains. In this study, another class of cyclic peptide, pyoverdine, was isolated from MIS38, viz., Pvd38. The main fraction of Pvd38 had an m/z value of 1,064.57 and contained Ala, Glu, Gly, (OHOrn), Ser, and Thr at a ratio of 2:1:1:(1):1:1 in the peptide part, suggesting a new structure compound. A gene encoding NRPS for the chromophore part of Pvd38 was identified, and we found that it contained a conventional E-domain. Gene disruption completely impaired the production of Pvd38, demonstrating that the synthetase is functional. This observation allows us to conclude that different NRPS systems with dual C/E-domains (in arthrofactin synthetase) and a conventional E-domain (in pyoverdine synthetase) are both functional in MIS38.     

Optimization of phenazine-1-carboxylic acid production by a gacA/qscR-inactivated Pseudomonas sp. M18GQ harboring pME6032Phz using response surface methodology

Phenazine-1-carboxylic acid (PCA) production was enhanced in Pseudomonas sp. M18 wild strain and its mutants carrying recombinant pME6032Phz for phz gene cluster overexpression, among which Pseudomonas sp. strain M18GQ/pME6032Phz, a gacA and qscR double gene chromosomally inactivated mutant harboring pME6032Phz, showed the highest PCA yield. The conditions for fermentation and isopropyl-β-d-1-thiogalactopyranoside (IPTG) induction were optimized for strain M18GQ/pME6032Phz in shake flask experiments. A one-factor-at-a-time approach, followed by a fractional factorial design identified soybean meal, corn steep liquor, and ethanol as statistically significant factors. Optimal concentrations and mutual interactions of the factors were then determined by the method of steepest ascent and by response surface methodology based on the center composite design. The predicted PCA production was 6,335.2 mg/l after 60 h fermentation in the optimal medium of 65.02 g soybean meal, 15.36 g corn steep liquor, 12 g glucose, 21.70 ml ethanol, and 1 g MgSO₄ per liter in the flask fermentations, with induction of 1.0 mmol/l IPTG 24 h after inoculation. In an experimental validation under these conditions, the maximum PCA production was 6,365.0 mg/l. This represents a ∼60% increase over production by strain M18GQ in optimal conditions. The negative effect of plasmid pME6032 on the expression of chromosomally located phz gene cluster was found in Pseudomonas sp. M18GQ, and the possible reason was discussed in the text.     

Biosurfactant-producing Bacillus are present in produced brines from Oklahoma oil reservoirs with a wide range of salinities

Nine wells producing from six different reservoirs with salinities ranging from 2.1% to 15.9% were surveyed for presence of surface-active compounds and biosurfactant-producing microbes. Degenerate primers were designed to detect the presence of the surfactin/lichenysin (srfA3/licA3) gene involved in lipopeptide biosurfactant production in members of Bacillus subtilis/licheniformis group and the rhlR gene involved in regulation of rhamnolipid production in pseudomonads. Polymerase chain reaction amplification, cloning, and sequencing confirmed the presence of the srfA3/licA3 genes in brines collected from all nine wells. The presence of B. subtilis/licheniformis strains was confirmed by sequencing two other genes commonly used for taxonomic identification of bacteria, gyrA (gyrase A) and the 16S rRNA gene. Neither rhlR nor 16S rRNA gene related to pseudomonads was detected in any of the brines. Intrinsic levels of surface-active compounds in brines were low or not detected, but biosurfactant production could be stimulated by nutrient addition. Supplementation with a known biosurfactant-producing Bacillus strain together with nutrients increased biosurfactant production. The genetic potential to produce lipopeptide biosurfactants (e.g., srfA3/licA3 gene) is prevalent, and nutrient addition stimulated biosurfactant production in brines from diverse reservoirs, suggesting that a biostimulation approach for biosurfactant-mediated oil recovery may be technically feasible.     

Isolation,purification, and characterization of novel fengycin S from <Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> LSC04 degrading-crude oil

In this study, a biosurfactant-producing bacterial strain was isolated from oil-contaminated soil on the basis of its ability to degrade crude oil and tributyrin (C_4:0). LSC04 was identified as Bacillus amyloliquefaciens LSC04 via 16S rRNA gene analysis and partial gyrA gene sequence analysis. The biosurfactants were purified and structural analysis results showed that B. amyloliquefaciens LSC04 generated a lipopeptide biosurfactant. Two main ions of 1,086.9 and 1,491.2 were measured via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The m/z 1,491.2 was shown to correspond to the lipopeptide fengycin B, but the m/z 1,086.9 ion did not correspond to any known lipopeptide. As constituents of the peptides and the lipophilic portion of the m/z 1,491.2; 10 amino acids (Ile-Tyr-Gln-Pro-Val-Glu-Ser-Tyr-Orn-Glu); and β-hydroxy-C17 fatty acid were identified via ESI-MS/MS. Structurally, the lipopeptide of a molecular mass of 1,491.2 differed from fengycin B and fengycin A by a substitution of serine for the threonine residue in position 4, and the amino acid residue in position 6 was equal to that of fengycin A. The major compound, which had a molecular mass of 1,491.2 Da was designated “Fengycin S”.     

Capacity for biosurfactant production of environmental Pseudomonas and Vibrionaceae growing on carbohydrates

Summary Pseudomonas and Vibrionaceae strains with the capacity to produce biosurfactants when growing on sucrose were isolated from the environment by a simple screening procedure. Agargrown colonies were randomly selected; each colony was suspended in a water droplet on a microscope slide. The tested strain was regarded as positive if the droplet spread over the surface.1779 Pseudomonas and 660 Vibrionaceae isolates were tested; 1% and 0.8% of the isolates, respectively, were positive for biosurfactant production. No production was detected amongst the isolates of a control group of 538 Gram-positive and 1063 Gram-negative strains.Four biosurfactant producing strains were grown in fermenter cultures on a semisynthetic medium using sucrose as carbon and energy source. The terminal concentrations of biosurfactants were in the range of a factor 40 times the critical micelle dilution. One P. fluorescens strain was grown in a carbon limited chemostat (succinate). The biosurfactant production was successively decreasing until it stopped after less than ten generation times.     

Simultaneous phenanthrene and cadmium removal from contaminated soil by a ligand/biosurfactant solution

Surfactants and inorganic ligands are pointed as efficient to simultaneous removal of heavy metals and hydrophobic organic pollutants from soil. However, the biosurfactants are potentially less toxic to soil organisms than other chemical agents. Thus, in this study the efficiency of combinations of iodide (I⁻) ligand and surfactants produced by different bacterial species in the simultaneous removal of cadmium (Cd²⁺) and phenanthrene in a Haplustox soil sample was investigated. Four microbial surfactants and the synthetic surfactant Triton X-100 were tested with different concentrations of ligand. Soil samples contaminated with Cd²⁺ and phenanthrene underwent consecutive washings with a surfactant/ligand solution. The removal of Cd²⁺ increased with increased ligand concentration, particularly in solutions containing biosurfactants produced by the bacterial strains Bacillus subtilis LBBMA155 (lipopeptide) and Flavobacterium sp. LBBMA168 (mixture of flavolipids) and Triton X-100. Maximum Cd²⁺ removal efficiency was 99.2% for biosurfactant produced by Arthrobacter oxydans LBBMA 201 (lipopeptide) and 99.2% for biosurfactant produced by Bacillus sp. LBBMA111A (mixed lipopeptide) in the presence of 0.336 mol iodide l⁻¹, while the maximum efficiency of Triton X-100 removal was 65.0%. The biosurfactant solutions removed from 80 to 88.0% of phenanthrene in soil, and the removal was not influenced by the presence of the ligand. Triton X-100 removed from 73 to 88% of the phenanthrene and, differently from the biosurfactants, iodide influenced the removal efficiency. The results indicate that the use of a single washing agent, called surfactant-ligand, affords simultaneous removal of organic contaminants and heavy metals.     

Suppression of disease in tomato infected by <Emphasis Type="Italic">Pythium ultimum</Emphasis> with a biosurfactant produced by <Emphasis Type="Italic">Pseudomonas koreensis</Emphasis>

The use of biosurfactants is a promising alternative in biological control of zoospore-producing oomycetes, which are a major plant pathogen world-wide in a wide variety of crops. Oomycetes are of particular concern in closed hydroponic cultivation systems. The present study investigated the efficacy of a biosurfactant produced by Pseudomonas koreensis and added as a crude extract against the oomycete Pythium ultimum in hydroponic tomato cultivation. A significant reduction in disease was observed. Biosurfactant addition did not affect the indigenous root microflora when evaluated as sole carbon source utilisation. Chemical analysis, using electrospray hybrid mass spectrometry (ESI-MSMS), of the biosurfactant indicated it to be lokisin, a cyclic lipopeptide. These results confirm that biosurfactants are important in developing sustainable biological control strategies for oomycetes.     

The Potential of Bacterial Isolates for Emulsification with a Range of Hydrocarbons

A study was undertaken to investigate the distribution of biosurfactant producing and crude oil degrading bacteria in the oil contaminated environment. This research revealed that hydrocarbon contaminated sites are the potent sources for oil degraders. Among 32 oil degrading bacteria isolated from ten different oil contaminated sites of gasoline and diesel fuel stations, 80% exhibited biosurfactant production. The quantity and emulsification activity of the biosurfactants varied. Pseudomonas sp. DS10‐129 produced a maximum of 7.5 ± 0.4 g/l of biosurfactant with a corresponding reduction in surface tension from 68 mN/m to 29.4 ± 0.7 mN/m at 84 h incubation. The isolates Micrococcus sp. GS2‐22, Bacillus sp. DS6‐86, Corynebacterium sp. GS5‐66, Flavobacterium sp. DS5‐73, Pseudomonas sp. DS10‐129, Pseudomonas sp. DS9‐119 and Acinetobacter sp. DS5‐74 emulsified xylene, benzene, n‐hexane, Bombay High crude oil, kerosene, gasoline, diesel fuel and olive oil. The first five of the above isolates had the highest emulsification activity and crude oil degradation ability and were selected for the preparation of a mixed bacterial consortium, which was also an efficient biosurfactant producing oil emulsifying and degrading culture. During this study, biosurfactant production and emulsification activity were detected in Moraxella sp., Flavobacterium sp. and in a mixed bacterial consortium, which have not been reported before.     

Antimicrobial potential of a lipopeptide biosurfactant derived from a marine Bacillus circulans

Aims: To isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials. Methods and Results: The marine isolate B. circulans was cultivated in glucose mineral salts medium and the crude biosurfactant was isolated by chemical isolation method. The crude biosurfactants were solvent extracted with methanol and the methanol extract was subjected to reverse phase high‐performance liquid chromatography (HPLC). The crude biosurfactants resolved into six major fractions in HPLC. The sixth HPLC fraction eluting at a retention time of 27·3 min showed the maximum surface tension‐reducing property and reduced the surface tension of water from 72 mNm^?1 to 28 mNm^?1. Only this fraction was found to posses bioactivity and showed a pronounced antimicrobial action against a panel of Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic micro‐organisms including a few multidrug‐resistant (MDR) pathogenic clinical isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of this antimicrobial fraction of the biosurfactant were determined for these test organisms. The biosurfactant was found to be active against Gram‐negative bacteria such as Proteus vulgaris and Alcaligens faecalis at a concentration as low as 10 μg ml^?1. The biosurfactant was also active against methicillin‐resistant Staphylococcus aureus (MRSA) and other MDR pathogenic strains. The chemical identity of this bioactive biosurfactant fraction was determined by post chromatographic detection using thin layer chromatography (TLC) and also by Fourier transform infrared (FTIR) spectroscopy. The antimicrobial HPLC fraction resolved as a single spot on TLC and showed positive reaction with ninhydrin, iodine and rhodamine‐B reagents, indicating its lipopeptide nature. IR absorption by this fraction also showed similar and overlapping patterns with that of other lipopeptide biosurfactants such as surfactin and lichenysin, proving this biosurfactant fraction to be a lipopeptide. The biosurfactant did not show any haemolytic activity when tested on blood agar plates, unlike the lipopeptide biosurfactant surfactin produced by Bacillus subtilis. Conclusions: The biosurfactant produced by marine B. circulans had a potent antimicrobial activity against Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic microbial strains including MDR strains. Only one of the HPLC fractions of the crude biosurfactants was responsible for its antimicrobial action. The antimicrobial lipopeptide biosurfactant fraction was also found to be nonhaemolytic in nature. Significance and impact of the study: This work presents a nonhaemolytic lipopeptide biosurfactant produced by a marine micro‐organism possessing a pronounced antimicrobial action against a wide range of bacteria. There is a high demand for new antimicrobial agents because of the increased resistance shown by pathogenic micro‐organisms against the existing antimicrobial drugs. This study provides an insight into the search of new bioactive molecules from marine micro‐organisms.     

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

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

     

Antimicrobial biosurfactants from marine Bacillus circulans: extracellular synthesis and purification

Aims:  To purify the biosurfactant produced by a marine Bacillus circulans strain and evaluate the improvement in surface and antimicrobial activities.
Methods and Results:  The study of biosurfactant production by B. circulans was carried out in glucose mineral salts (GMS) medium using high performance thin layer chromatography (HPTLC) for quantitative estimation. The biosurfactant production by this strain was found to be growth-associated showing maximum biosurfactant accumulation at 26 h of fermentation. The crude biosurfactants were purified using gel filtration chromatography with Sephadex^® G-50 matrix. The purification attained by employing this technique was evident from UV–visible spectroscopy and TLC analysis of crude and purified biosurfactants. The purified biosurfactants showed an increase in surface activity and a decrease in critical micelle concentration values. The antimicrobial action of the biosurfactants was also enhanced after purification.
Conclusions:  The marine B. circulans used in this study produced biosurfactants in a growth-associated manner. High degree of purification could be obtained by using gel filtration chromatography. The purified biosurfactants showed enhanced surface and antimicrobial activities.
Significance and Impact of the Study:  The antimicrobial biosurfactant produced by B. circulans could be effectively purified using gel filtration and can serve as new potential drugs in antimicrobial chemotherapy.     

Functional analysis of a pyoverdine synthetase from Pseudomonas sp. MIS38

Fluorescent Pseudomonas sp. MIS38 produces a cyclic lipopeptide, arthrofactin. Arthrofactin is synthesized by a unique nonribosomal peptide synthetase (NRPS) with dual C/E-domains. In this study, another class of cyclic peptide, pyoverdine, was isolated from MIS38, viz., Pvd38. The main fraction of Pvd38 had an m/z value of 1,064.57 and contained Ala, Glu, Gly, (OHOrn), Ser, and Thr at a ratio of 2:1:1:(1):1:1 in the peptide part, suggesting a new structure compound. A gene encoding NRPS for the chromophore part of Pvd38 was identified, and we found that it contained a conventional E-domain. Gene disruption completely impaired the production of Pvd38, demonstrating that the synthetase is functional. This observation allows us to conclude that different NRPS systems with dual C/E-domains (in arthrofactin synthetase) and a conventional E-domain (in pyoverdine synthetase) are both functional in MIS38.     

A novel lipopeptide produced by a Pacific Ocean deep-sea bacterium, Rhodococcus sp. TW53

Aims: Our goal was to find a novel, biosurfactant‐producing bacterium from Pacific Ocean deep‐sea sediments. Methods and Results: An oil‐degrading biosurfactant‐producing bacterium TW53 was obtained from deep‐sea sediment, and was identified through 16S rDNA analysis as belonging to the genus Rhodococcus. It lowered the surface tension of its culture to 34·4 mN m^?1. Thin layer chromatography (TLC) showed that the crude biosurfactants of TW53 were composed of lipopeptides and free fatty acids (FA). The lipopeptides were purified with column chromatography and then hydrolysed with 6 mol l^?1 HCl. Gas chromatography‐mass spectrometry analysis showed that the hydrolyte in the hydrophobic fraction contained five kinds of FA with chain lengths of C₁₄–C₁₉, and C₁₆H₃₂O₂ was a major component making up 59·18% of the total. However, 3‐hydroxyl FA was not found, although it is usually found in lipopeptides. Silica gel TLC revealed that the hydrolyte in the hydrophilic fraction was composed of five kinds of amino acids; consistently, ESI‐Q‐TOF‐MS analysis confirmed the composition results and provided their sequence tentatively as Ala‐Ile‐Asp‐Met‐Pro. Furthermore, the yield and CMC (critical micelle concentrations) of purified lipopeptides were examined. The purified product reduced the surface tension of water to 30·7 mN m^?1 with a CMC value of 23·7 mg l^?1. These results suggest that Rhodococcus sp. TW53 produces a novel lipopeptide that we have named rhodofactin. Conclusion: The deep‐sea isolate Rhodococcus sp. TW53 was the first reported lipopeptide‐producing bacterium of this genus. The lipopeptides had novel chemical compositions. Significance and Impact of the Study: Rhodococcus sp. TW53 has potential in the exploration of new biosurfactants and could be used in bioremediation of marine oil pollution.     

A truncated form of SpoT, including the ACT domain, inhibits the production of cyclic lipopeptide arthrofactin, and is associated with moderate elevation of guanosine 3',5'-bispyrophosphate level in Pseudomonas sp. MIS38

Arthrofactin is a biosurfactant produced by Pseudomonas sp. MIS38. We have reported that transposon insertion into spoT (spoT::Tn5) causes moderate accumulation of guanosine 3',5'-bispyrophosphate (ppGpp) and abrogates arthrofactin production. To analyze the linkage of SpoT function and ablation of arthrofactin production, we examined the spoT::Tn5 mutation. The results showed that spoT::Tn5 is not a null mutation, but encodes separate segments of SpoT. Deletion of the 3' region of spoT increased the level of arthrofactin production, suggesting that the C-terminal region of SpoT plays a suppressive role. We evaluated the expression of a distinct segment of SpoT. Forced expression of the C-terminal region that contains the ACT domain resulted in the accumulation of ppGpp and abrogated arthrofactin production. Expression of the C-terminal segment also reduced MIS38 swarming and resulted in extensive biofilm formation, which constitutes the phenocopy of the spoT::Tn5 mutant.     

Effect of two types of biosurfactants on phenanthrene availability to the bacterial bioreporter Burkholderia sartisoli strain RP037

Biosurfactants are tensio-active agents that have often been proposed as a means to enhance the aqueous solubility of hydrophobic organic contaminants, such as polycyclic aromatic hydrocarbons (PAHs). Biosurfactant-producing bacteria such as those belonging to the genus Pseudomonas might therefore enhance PAH availability to PAH-degrading bacteria. We tested the effects of two types of biosurfactants produced by Pseudomonas sp., cyclic lipopeptides and rhamnolipids, on phenanthrene bioavailability. Bioavailability was judged from growth rates on phenanthrene and from specific induction of a phenanthrene-responsive GFP-reporter in Burkholderia sartisoli strain RP037. Co-culturing of strain RP037 with the lipopeptide-producing bacterium Pseudomonas putida strain PCL1445 enhanced GFP expression compared to a single culture, but this effect was not significantly different when strain RP037 was co-cultivated with a non-lipopeptide-producing mutant of P. putida. The addition of partially purified supernatant extracts from the P. putida lipopeptide producer equally did not unequivocally enhance phenanthrene bioavailability to strain RP037 compared to controls. In contrast, a 0.1% rhamnolipid solution strongly augmented RP037 growth rates on phenanthrene and led to a significantly larger proportion of cells in culture with high GFP expression. Our data therefore suggest that biosurfactant effects may be strongly dependent on the strain and type of biosurfactant.     

Isolation and characterization of a biosurfactant‐producing Fusarium sp. BS‐8 from oil contaminated soil

This study reports characterization of a biosurfactant‐producing fungal isolate from oil contaminated soil of Missa Keswal oil field, Pakistan. It was identified as Fusarium sp. BS‐8 on the basis of macroscopic and microscopic morphology, and 18S rDNA gene sequence homology. The biosurfactant‐producing capability of the fungal isolates was screened using oil displacement activity, emulsification index assay, and surface tension (SFT) measurement. The optimization of operational parameters and culture conditions resulted in maximum biosurfactant production using 9% (v/v) inoculum at 30°C, pH 7.0, using sucrose and yeast extract, as carbon and nitrogen sources, respectively. A C:N ratio of 0.9:0.1 (w/w) was found to be optimum for growth and biosurfactant production. At optimal conditions, it attained lowest SFT (i.e., 32 mN m^?1) with a critical micelle concentration of ≥ 1.2 mg mL^?1. During 5 L shake flask fermentation experiments, the biosurfactant productivity was 1.21 g L^?1 pure biosurfactant having significant emulsifying index (E₂₄, 70%) and oil‐displacing activity (16 mm). Thin layer chromatography and Fourier transform infrared spectrometric analyses indicated a lipopeptide type of the biosurfactant. The Fusarium sp. BS‐8 has substantial potential of biosurfactant production, yet it needs to be fully characterized with possibility of relatively new class of biosurfactants. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1065–1075, 2014     

Isolation and characterization of hydrocarbon-degrading and biosurfactant-producing yeast strains obtained from a polluted lagoon water

Microbial surfactants are environmentally friendly products with amazing properties and spectrum of applications. It is therefore, not surprising that research has increased in recent time with the objectives of sourcing for novel surface-active compounds with dual functions in oil and pharmaceutical industries. Evaluation of hydrocarbon degrading potentials and emulsifying activities indicated that biosurfactants were produced by two newly isolated and promising yeast strains, Saccharomyces cerevisiae and Candida albicans, obtained from a polluted lagoon water. Both strains were able to grow effectively on crude oil and diesel as sole sources of carbon and energy. Growth curves on diesel were obtained to establish the relation between cell growth and biosurfactant production. The growth peak was on the 8th day while the specific growth rate ranged insignificantly (P < 0.05) between 0.46 and 0.48 day⁻¹. Interestingly, biosurfactant was detected on the 2nd day when growth was almost inexistent, with maximal production obtained at stationary/death phase of growth. The partially-purified biosurfactants exhibited antimicrobial activities by completely inhibiting the growth of clinical strains of Escherichia coli and Staphylococcus aureus at all concentrations tested. Although C. albicans appeared to be a better diesel-utilizer and biosurfactant-producer (E₂₄ = 64.2%), the potency of its surfactant was smaller than that of S. cerevisiae. These strains represent a new class of biosurfactant producers that have potential for use in a variety of biotechnological and industrial processes particularly in the pharmaceutical industry.