Effect of different non-ionic surfactants on the biodegradation of PAHs by diverse aerobic bacteria

The aim of this work was to evaluate the effect of several non-ionic surfactants (Tween-80, Triton X-100 and Tergitol NP-10) on the ability of different bacteria (Enterobacter sp., Pseudomonas sp. and Stenotrophomonas sp.) to degrade polycyclic aromatic hydrocarbons (PAHs). Bacterial cultures were performed at 25 °C in an orbital shaker under dark conditions in BHB medium containing 1% of surfactant and 500 mg l⁻¹ of each PAH. Experiments performed with Tween-80 showed the highest cell density values and maximum specific growth rate because this surfactant was used as a carbon source by all bacteria. High degree of PAHs degradation (>90%) was reached in 15 days in all experiments. Toxicity increased at early times using Tween-80 but decreased to low levels in a short time after the firsts 24 h. On the other hand, Triton X-100 and Tergitol NP-10 were not biodegraded and toxicity kept constant along time. However, PAHs-degradation rate was higher, especially by the action of Enterobacter sp. with Tween-80 or Triton X-100. Control experiments performed without surfactant showed a significant decrease in biomass growth rate with a subsequent loss of biodegradation activity likely due to a reduced solubility and bioavailability of PAHs in absence of surfactant.     

Inhibition of Aflatoxin Production by Surfactants

The effect of 12 surfactants on aflatoxin production, growth, and conidial germination by the fungus Aspergillus flavus is reported. Five nonionic surfactants, Triton X-100, Tergitol NP-7, Tergitol NP-10, polyoxyethylene (POE) 10 lauryl ether, and Latron AG-98, reduced aflatoxin production by 96 to 99% at 1% (wt/vol). Colony growth was restricted by the five nonionic surfactants at this concentration. Aflatoxin production was inhibited 31 to 53% by lower concentrations of Triton X-100 (0.001 to 0.0001%) at which colony growth was not affected. Triton X-301, a POE-derived anionic surfactant, had an effect on colony growth and aflatoxin production similar to that of the five POE-derived nonionic surfactants. Sodium dodecyl sulfate (SDS), an anionic surfactant, and dodecyltrimethylammonium bromide, a cationic surfactant, suppressed conidial germination at 1% (wt/vol). SDS had no effect on aflatoxin production or colony growth at 0.001%. The degree of aflatoxin inhibition by a surfactant appears to be a function of the length of the hydrophobic and hydrophilic chains of POE-derived surfactants.     

Biosurfactant-rhamnolipid effects on yeast cells

AIM: The aim of this work was to study the effect of the novel surfactant PS from Pseudomonas sp. S-17 on Saccharomyces cerevisiae 83-20 yeast cells and to compare it with the effect of the well known surfactant Triton X-100. METHODS AND RESULTS: The effect of surfactants was investigated on the cells during growth, and on the separated cells. The cell-permeabilizing effect of surfactants was studied by following the release of protein and some enzyme activities. The biosurfactant did not affect the culture growth kinetics, and altered the polypeptide profiles of cells and membrane proteins in the same way as Triton X-100. CONCLUSION: Results of this study demonstrate that biosurfactant PS and Triton X-100 have a similar type of action, mainly surface located, and that they do not affect the intracellular structures of yeast cells. SIGNIFICANCE AND IMPACT OF THE STUDY: A novel surfactant PS was isolated from Pseudomonas sp. S-17. A mild effect of PS on yeast cells was demonstrated. The results indicate the ecological safety of the biosurfactant and its potential use in the development of environmentally-benign and efficient cleaning technologies.     

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.     

Co-degradation with glucose of four surfactants,CTAB, Triton X-100, SDS and Rhamnolipid,in liquid culture media and compost matrix

Strengthened biodegradation is one of the key means to treat surfactant pollution in environment, and microorganism and surfactant have significant effects on degradation. In this paper, co-degradation of CTAB, Triton X-100, SDS and rhamnolipid with glucose by Pseudomonas aeruginosa, Bacillus subtilis and compost microorganisms in liquid culture media, as well as the degradation of rhamnolipid in compost were investigated. The results showed that CTAB was recalcitrant to degrade by the three microorganisms and it also inhibited microorganisms from utilizing readily degradable carbon source. Non-ionic surfactant Triton X-100 could also hardly be degraded, but it was not toxic to microorganisms and would not inhibit the growth of the microorganisms. Anion surfactant SDS had no toxicity to microorganisms and could be co-degraded as carbon source with glucose. Biosurfactant rhamnolipid was a kind of particular surfactant, which had no toxicity and could be degraded by Bacillus subtilis and compost microorganisms, while it could not be utilized by its producing bacterium Pseudomonas aeruginosa. Among these three bacteria, the compost consortium had the strongest degradation capacity on the tested surfactants due to their microorganisms’ diversity. In compost matrix rhamnolipid could be degraded during composting, but not preferentially utilized.     

Molecular characterization of surfactant-driven microbial community changes in anaerobic phenanthrene-degrading cultures under methanogenic conditions

SDS and Triton X-100 added at their critical micelle concentrations (CMCs), increased phenanthrene solubility in the presence of sediments and inhibited phenanthrene biodegradation. Triton X-100 caused more inhibition than SDS. 16S rDNA analyses revealed that both surfactants changed the microbial communities of phenanthrene-degrading cultures. Further, after the surfactant additions, parts of the microbial populations were not detected and methane production decreased. Surfactant applications, necessary to achieve actual CMCs, alter microbial community structure and diminish methanogenic activity under anaerobic conditions. We propose that this change may be related to the inhibitory effects of SDS and Triton X-100 on phenanthrene biodegradation under methanogenic conditions.     

Stabilization of Crystalline Acid Carboxypeptidase from Penicillium janthinellum by Nonionic Surfactants,and Inhibition of Enzyme Activity by Anionic Compounds

The crystalline acid carboxypeptidase from Penicillium janthinellum IFO-8070 was stabilized by the addition of nonionic surfactants, such as Triton X-100, Brij 35, Span 40, and Tween 20. In the presence of these stabilizers, extremely diluted enzyme (0.3 μg/ml of 50 mm sodium acetate buffer, pH 3.7) was almost completely stable after 2 days incubation at 25°C. About 35% and 20% of the enzyme activities were activated by the addition of Triton X-100 and Brij 35, respectively. Triton X-100 completely retarded inactivation at freezing (?15°C). On the other hand, anionic surfactants of SLS and LBSA, and cationic surfactant of cetyltrimethylammonium bromide strongly inactivated the enzyme. The inhibition of the fatty acid series was roughly proportional to the molecular weight of the inhibitor. Di-, and Tri-carboxylic acids also inhibited the enzyme activity.     

Enzyme production by growing cells of acinetobacter in presence of sophoroselipid and triton X-100

The effects of an extracellular microbial glycolipid, the interfacial active lactonic sophoroselipid, and of Triton X-100 on strains of Acinetobacter calcoaceticus are compared. Sophoroselipid diminished growth rates on n-heptadecane. Both surfactants led to the excretion of enzyme activities into the culture medium. Sophoroselipid increased the release of cytoplasmic malate dehydrogenase whereas in presence of Triton X-100 the quinoprotein glucose dehydrogenase was also excreted in large amounts.     

Assessing bioavailability of the solubilization of organic compound in nonionic surfactant micelles by dose–response analysis

It is uncertain in some extent that organic compounds solubilized in micelles of a nonionic surfactant aqueous solution are bioavailable directly by the microbes in an extractive microbial transformation or biodegradation process. In this work, a dose–response method, where a bioequivalence concept is introduced to evaluate the synergic toxicity of the nonionic surfactants and the organic compounds, was applied to analyze the inhibition effect of organic compounds (naphthalene, phenyl ether, 2-phenylethanol, and 1-butanol) in nonionic surfactant Triton X-100 micelle aqueous solutions and Triton X-114 in aqueous solutions forming cloud point systems. Based on the result, a mole solubilization ratio of organic compounds in micelle was also determined, which consisted very well with those of classic semi-equilibrium dialysis experiments. The results exhibit that bioavailability of organic compounds solubilized in micelles to microbial cells is negligible, which provides a guideline for application of nonionic surfactant micelle aqueous solutions or cloud point systems as novel media for microbial transformations or biodegradations.     

Influence of nonionic surfactants and hydroxypropyl-β-cyclodextrin on the biodegradation of nitrobenzene

This paper investigates the effect of two nonionic surfactants (Tween 80 and Triton X-100) and hydroxypropyl--cyclodextrin (HP--CD) on the biodegradation of nitrobenzene (NB) by Acinetobacter sp. in liquid cultures at different dosages as well as the fate of both surfactants. When the initial concentration of NB was about 400 mg/l, neither Tween 80 nor HP--CD had any effect on the degradation of NB. However, Triton X-100 retarded the full removal of NB and the bacterial growth entering the stationary phase. While the initial concentration of NB was increased to about 850 mg/l, they all significantly enhanced the extent and rate of biodegradation if they were added at concentrations above 2000 mg/l. HP--CD could not be utilized by Acinetobacter sp. as the sole carbon source whereas both surfactants could, but no surfactant depletion was observed during the biodegradation of NB. So the rapid bacterial growth observed in the presence of each additive should be attributed to the rapid metabolism of NB. Both surfactants would promote the degradation of NB more than HP--CD would do if their dosages were increased properly.     

Contrasting effects of a nonionic surfactant on the biotransformation of polycyclic aromatic hydrocarbons to cis-dihydrodiols by soil bacteria

The biotransformation of the polycyclic aromatic hydrocarbons (PAHs) naphthalene and phenanthrene was investigated by using two dioxygenase-expressing bacteria, Pseudomonas sp. strain 9816/11 and Sphingomonas yanoikuyae B8/36, under conditions which facilitate mass-transfer limited substrate oxidation. Both of these strains are mutants that accumulate cis-dihydrodiol metabolites under the reaction conditions used. The effects of the nonpolar solvent 2,2,4, 4,6,8,8-heptamethylnonane (HMN) and the nonionic surfactant Triton X-100 on the rate of accumulation of these metabolites were determined. HMN increased the rate of accumulation of metabolites for both microorganisms, with both substrates. The enhancement effect was most noticeable with phenanthrene, which has a lower aqueous solubility than naphthalene. Triton X-100 increased the rate of oxidation of the PAHs with strain 9816/11 with the effect being most noticeable when phenanthrene was used as a substrate. However, the surfactant inhibited the biotransformation of both naphthalene and phenanthrene with strain B8/36 under the same conditions. The observation that a nonionic surfactant could have such contrasting effects on PAH oxidation by different bacteria, which are known to be important for the degradation of these compounds in the environment, may explain why previous research on the application of the surfactants to PAH bioremediation has yielded inconclusive results. The surfactant inhibited growth of the wild-type strain S. yanoikuyae B1 on aromatic compounds but did not inhibit B8/36 dioxygenase enzyme activity in vitro.     

Response of fluoranthene-degrading bacteria to surfactants

A prerequisite for surfactant-enhanced biodegradation is that the microorganisms survive, take up substrate and degrade it in the presence of the surfactant. Two Mycobacterium and two Sphingomonas strains, degrading fluoranthene, were investigated for their sensitivity towards non-ionic chemical surfactants. The effect of Triton X-100 and Tween 80 above their critical micelle concentration on mineralization of [¹⁴C]-glucose and [¹⁴C]-fluoranthene was measured in shaker cultures. Tween 80 had no toxic effect on any of the tested strains. The surfactant inhibited fluoranthene mineralization by the hydrophobic Mycobacterium spp. slightly, but more than doubled that by the two less hydrophobic Sphingomonas strains. Triton X-100 inhibited fluoranthene mineralization by all strains, yet this was more pronounced for the Sphingomonas spp. Both surfactants caused cell wall permeabilization, as shown by transient colouring of surfactant-containing media. Inhibition of glucose mineralization, indicating non-specific toxic effects of Triton X-100, was observed only for the Sphingomonas strains and the toxicity was caused by micelle-to-cell interactions. These strains, however, appeared to recover from initial Triton X-100 toxicity within 50–500 h of exposure. The ratio of surfactant concentration to initial cell density was found to determine critically the bacterial response to surfactants. For both Sphingomonas and Mycobacterium strains, this work indicates that fluoranthene solubilized in surfactant micelles is only partially available for mineralization by the bacteria tested. However, our results suggest that optimal conditions for polycyclic aromatic hydrocarbon mineralization can be developed by selection of the proper surfactant, bacterial strains, cell density and incubation conditions. Received: 6 February 1998 / Received revision: 19 June 1998 / Accepted: 19 June 1998     

Investigation of extractive microbial transformation in nonionic surfactant micelle aqueous solution using response surface methodology

Extractive microbial transformation of L-phenylacetylcarbinol (L-PAC) in nonionic surfactant Triton X-100 micelle aqueous solution was investigated by response surface methodology. Based on the Box–Behnken design, a mathematical model was developed for the predication of mutual interactions between benzaldehyde, Triton X-100, and glucose on L-PAC production. It indicated that the negative or positive effect of nonionic surfactant strongly depended on the substrate concentration. The model predicted that the optimal concentration of benzaldehyde, Triton X-100, and glucose was 1.2 ml, 15 g, and 2.76 g per 100 ml, respectively. Under the optimal condition, the maximum L-PAC production was 27.6 mM, which was verified by a time course of extractive microbial transformation. A discrete fed-batch process for verification of cell activity was also presented.     

Adsorption of surfactants on a <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> strain and the effect on cell surface lypohydrophilic property

The adsorption behavior of five surfactants, cetyltrimethylammonium bromide (CTAB), Triton X-100, Tween 80, sodium dodecyl sulfate (SDS), and rhamnolipid, on a Pseudomonas aeruginosa strain and the effect of temperature and ionic strength (IS) on the adsorption were studied. The change of cell surface lypohydrophilic property caused by surfactant adsorption was also investigated. The results showed that the adsorption kinetics of the surfactants on the cell followed the second-order law. CTAB adsorption was the fastest one under the experimental conditions, and it took longest for SDS adsorption to equilibrate because of electric repulsion. The adsorption of Triton X-100 and Tween 80 was characterized by short equilibration time, and rhamnolipid adsorption reached equilibrium in about 90 min. The adsorption isotherms of all the surfactants on the bacterium fitted Freundlich equation well, but the adsorption capacity and mode were variations for the surfactants as indicated by k and n parameters in the equations. The adsorption mode for all the surfactants except SDS is probably hydrophilic interaction because the adsorption totally turned the cell surface to be more hydrophobic. Neither the temperature nor the IS had significant effect on CTAB adsorption, but higher IS significantly enhanced SDS adsorption and modestly strengthened adsorption of Triton X-100, Tween 80, and rhamnolipid. Higher temperature strengthened adsorption of SDS but weakened the adsorption of Triton X-100, Tween 80, and rhamnolipid.     

Alteration in cell surface properties of <Emphasis Type="Italic">Burkholderia</Emphasis> spp. during surfactant-aided biodegradation of petroleum hydrocarbons

Chemical surfactants may impact microbial cell surface properties, i.e., cell surface hydrophobicity (CSH) and cell surface charge, and may thus affect the uptake of components from non-aqueous phase liquids (NAPLs). This work explored the impact of Triton X-100, Igepal CA 630, and Tween 80 (at twice the critical micelle concentration, CMC) on the cell surface characteristics of Burkholderia cultures, Burkholderia cepacia (ES1, aliphatic degrader) and Burkholderia multivorans (NG1, aromatic degrader), when grown on a six-component model NAPL. In the presence of Triton X-100, NAPL biodegradation was enhanced from 21% to 60% in B. cepacia and from 18% to 53% in B. multivorans. CSH based on water contact angle (50–52°) was in the same range for both strains while zeta potential at neutral pH was −38 and −31 mV for B. cepacia and B. multivorans, respectively. In the presence of Triton X-100, their CSH increased to greater than 75° and the zeta potential decreased. This induced a change in the mode of uptake and initiated aliphatic hydrocarbon degradation by B. multivorans and increased the rate of aliphatic hydrocarbon degradation in B. cepacia. Igepal CA 630 and Tween 80 also altered the cell surface properties. For B. cepacia grown in the presence of Triton X-100 at two and five times its CMC, CSH increased significantly in the log growth phase. Growth in the presence of the chemical surfactants also affected the abundance of chemical functional groups on the cell surface. Cell surface changes had maximum impact on NAPL degradation in the presence of emulsifying surfactants, Triton X-100 and Igepal CA630.     

Extractive fermentation in cloud point system for lipase production by Serratia marcescens ECU1010

Extractive microbial fermentation for production of lipase by Serratia marcescens ECU1010 has been carried out in cloud point system. The cloud point system is composed of mixture nonionic surfactants with a ratio of Triton X-114 to Triton X-45 4:1 in aqueous solution. The lipase prefers to partition into the surfactant rich phase (coacervate phase) whereas the cells and other hydrophilic proteins retain in the dilute phase of cloud point system. Thus, a concentration factor 4.2-fold and a purification factor 1.3-fold of the lipase have been achieved in the extractive fermentation process. This is the first report about extractive fermentation of proteins in cloud point system.     

Cellular lysis of Streptococcus faecalis induced with triton X-100.

Lysis of exponential-phase cultures of Streptococcus faecalis ATCC 9790 was induced by exposure to both anionic (sodium dodecyl sulfate) and nonionic (Triton X-100) surfactants. Lysis in response to sodium dodecyl sulfate was effective only over a limited range of concentrations, whereas Triton X-100-induced lysis occurred over a broad range of surfactant concentrations. The data presented indicate that the bacteriolytic response of growing cells to Triton X-100: (i) was related to the ratio of surfactant to cells and not the surfactant concentration per se; (ii) required the expression of the cellular autolytic enzyme system; and (iii) was most likely due to an effect of the surfactant on components of the autolytic system that are associated with the cytoplasmic membrane. The possibility that Triton X-100 may induce cellular lysis by releasing a lipid inhibitor of the cellular autolytic enzyme is discussed.     

Bacterial Adhesion to Soil Contaminants in the Presence of Surfactants

It has been proposed that addition of surfactants to contaminated soil enhances the solubility of target compounds; however, surfactants may simultaneously reduce the adhesion of bacteria to hydrophobic surfaces. If the latter mechanism is important for the biodegradation of virtually insoluble contaminants, then the use of surfactants may not be beneficial. The adhesion of a Mycobacterium strain and a Pseudomonas strain, isolated from a creosote-contaminated soil, to the surfaces of highly viscous non-aqueous-phase liquids (NAPLs) was measured. The NAPLs were organic material extracted from soils from two creosote-contaminated sites and two petroleum-contaminated sites. Cells suspended in media with and without surfactant were placed in test tubes coated with an NAPL, and the percentages of cells that adhered to the surface of the NAPL in the presence and absence of surfactant were compared by measuring optical density. Test tubes without NAPLs were used as controls. The presence of either Triton X-100 or Dowfax 8390 at a concentration that was one-half the critical micelle concentration (CMC) inhibited adhesion of both species of bacteria to the NAPLs. Both surfactants, when added at concentrations that were one-half the CMCs to test tubes containing previously adhered bacteria, also promoted the removal of the cells from the surfaces of the NAPL-coated test tubes. Neither surfactant was toxic to the bacteria. Further investigation showed that a low concentration of surfactant also inhibited the growth of both species on anthracene, indicating that the presence of a surfactant resulted in a reduction in the uptake of the solid carbon source.     

Effects of different surfactants on motility and DNA integrity of brown trout (Salmo trutta fario) and common carp (Cyprinus carpio) spermatozoa

In this study we evaluated effects of surfactants on motility parameters and DNA integrity of spermatozoa of freshwater teleost fish. Common carp (Cyprinus carpio) and brown trout (Salmo trutta fario) spermatozoa were exposed to either sodium dodecyl sulphate (SDS, anionic surfactant) or octoxynol 9 ( Triton X-100, nonionic surfactant). Both surfactants added at activation caused a decrease in sperm motility characteristics measured by computer-assisted sperm analysis (CASA). Intraspecific differences in speed and trajectory of movement were detected. Triton X-100 and SDS when added to non activated sperm were also effective in the decrease of sperm motility and caused an increase of DNA fragmentation. Our results suggest that not only sperm motility apparatus but also DNA are targets for surfactant action. Therefore any exposure of spermatozoa to surfactants, in aquaculture conditions or natural environment, would have a negative impact on fish reproduction.     

Effects of Triton X-100 and Quillaya Saponin on the ex situ bioremediation of a chronically polychlorobiphenyl-contaminated soil

The possibility of enhancing the ex situ bioremediation of a chronically polychlorinated biphenyl (PCB)-contaminated soil by using Triton X-100 or Quillaya Saponin, a synthetic and a biogenic surfactant, respectively, was studied. The soil, which contained about 350 mg/kg of PCBs and indigenous aerobic bacteria capable of growing on biphenyl or on monochlorobenzoic acids, was amended with inorganic nutrients and biphenyl, saturated with water and treated in aerobic batch slurry- and fixed-phase reactors. Triton X-100 and Quillaya Saponin were added to the reactors at a final concentration of 10 g/l at the 42nd day of treatment, and at the 43rd and 100th day, respectively. Triton X-100 was not metabolised by the soil microflora and it exerted inhibitory effects on the indigenous bacteria. Quillaya Saponin, on the contrary, was readily metabolised by the soil microflora. Under slurry-phase conditions, Triton X-100 negatively influenced the soil bioremediation process by affecting the availability of the chlorobenzoic acid degrading indigenous bacteria, whereas Quillaya Saponin slightly enhanced the biological degradation and dechlorination of the soil PCBs. In the fixed-phase reactors, where both the surfactant availability and the mixing of the soil were lower, Triton X-100 did not exert inhibitory effects on the soil biomass and enhanced significantly the soil PCB depletion, whereas Quillaya Saponin did not influence the bioremediation process. Received: 28 April 1998 / Received last revision: 15 July 1998 / Accepted: 29 July 1998