Bioavailability of organic compounds solubilized in nonionic surfactant micelles

Oil-water interfaces of Pickering emulsions: microhabitats for living cell biocatalysis

Based on the size of bacterial cells and bacterial surface hydrophobicity, some bacteria meet the requirements of Pickering particles to stabilize Pickering emulsions. Here, we discuss the oil-water interfaces of bacteria-stabilized Pickering emulsions as microhabitats for microbial metabolism of oil-soluble chemicals. The correlation between living bacteria-stabilized Pickering emulsions and microhabitats of living bacteria at oil-water interfaces offers a new perspective to study bioprocess engineering at the mesoscale between the cell and reactor scales, which not only provides novel parameters to optimize the bioprocess engineering, but also unravels the paradox of some natural phenomena related to living cell biocatalysis.

Surfactants Influencing the Biocatalytic Performance of Natural Alkane-Degrading Bacteria via Interfacial Biocatalysis in Pickering Emulsions

Setting superhydrophobic Mycobacterium sp. as an example, the hydrophobic bacteria acting as demulsifying agents of surfactant-stabilized conventional emulsions, vice versa, the synergistic/antagonistic influence of nonionic surfactants (Tween 80 or Span 80) on the stability of the bacteria-stabilized Pickering emulsions was investigated. At the same time, the activated/suppression effect of nonionic surfactants on microbial degradation of tetradecane, which exhibited a dose-response relationship, was also found. The hydrophobic bacteria acting as demulsifying agents and the suppression influence of nonionic surfactants on the biocatalytic performance (indexing as biomass) of natural alkane-degrading bacteria, believed to be totally separated concepts previously, are for the first time found to be closely related to in situ surface modification of bacteria with nonionic surfactants. During the degradation of tetradecane by Mycobacterium sp. in the presence of nonionic surfactants, demulsification due to the bacteria acting as demulsifying agents and interfacial biocatalysis in the bacteria-stabilized Pickering emulsions are involved, which provides useful information to select optimal dispersants for marine oil spills.

Enhancing Soluble Expression of Phospholipase B for Efficient Catalytic Synthesis of L-Alpha-Glycerylphosphorylcholine

Phospholipase B (PLB) harbors three distinct activities with broad substrate specificities and application fields. Its hydrolyzing of sn-1 and sn-2 acyl ester bonds enables it to catalyze the production of L-alpha-glycerylphosphorylcholine (L-α-GPC) from phosphatidylcholine (PC) without speed-limiting acyl migration. This work was intended to obtain high-level active PLB and apply it to establish an efficient system for L-α-GPC synthesis. PLB from Pseudomonas fluorescens was co-expressed with five different molecular chaperones, including trigger factor (Tf), GroEL-GroES (GroELS), DnaK-DnaJ-GrpE (DnaKJE), GroELS and DnaKJE, or GroELS and Tf or fused with maltose binding protein (MBP) in Escherichia coli BL21(DE3) to improve PLB expression. PLB with DnaKJE-assisted expression exhibited the highest catalytic activity. Further optimization of the expression conditions identified an optimal induction OD600 of 0.8, IPTG concentration of 0.3 mmol/L, induction time of 9 h, and temperature of 25 °C. The PLB activity reached a maximum of 524.64 ± 3.28 U/mg under optimal conditions. Subsequently, to establish an efficient PLB-catalyzed system for L-α-GPC synthesis, a series of organic-aqueous mixed systems and surfactant-supplemented aqueous systems were designed and constructed. Furthermore, the factors of temperature, reaction pH, metal ions, and substrate concentration were further systematically identified. Finally, a high yield of 90.50 ± 2.21% was obtained in a Span 60-supplemented aqueous system at 40 °C and pH 6.0 with 0.1 mmol/L of Mg2+. The proposed cost-effective PLB production and an environmentally friendly PLB-catalyzed system offer a candidate strategy for the industrial production of L-α-GPC.

Formulation of More Efficacious Curcumin Delivery Systems Using Colloid Science: Enhanced Solubility, Stability, and Bioavailability

Curcumin is a bioactive constituent isolated from turmeric that has historically been used as a seasoning, pigment, and herbal medicine in food. Recently, it has become one of the most commonly studied nutraceuticals in the pharmaceutical, supplement, and food areas because of its myriad of potential health benefits. For instance, it is claimed to exhibit antioxidant, anti-inflammatory, antimicrobial, antiparasite, and anticancer activities when ingested as a drug, supplement, or food. Toxicity studies suggest that it is safe to consume, even at relatively high levels. Its broad-spectrum biological activities and low toxicity have meant that it has been widely explored as a nutraceutical ingredient for application in functional foods. However, there are several hurdles that formulators must overcome when incorporating curcumin into commercial products, such as its low water solubility (especially under acidic and neutral conditions), chemical instability (especially under neutral and alkaline conditions), rapid metabolism by enzymes in the human body, and limited bioavailability. As a result, only a small fraction of ingested curcumin is actually absorbed into the bloodstream. These hurdles can be at least partially overcome by using encapsulation technologies, which involve trapping the curcumin within small particles. Some of the most commonly used edible microparticles or nanoparticles utilized for this purpose are micelles, liposomes, emulsions, solid lipid particles, and biopolymer particles. Each of these encapsulation technologies has its own benefits and limitations for particular product applications and it is important to select the most appropriate one.

Merging of a chemical reaction with microbial metabolismviainverse phase transfer catalysis for efficient production of redMonascuspigments

Cascade reactions,i.e., biosynthesis of OMPs and chemical modification of hydrophobic OMPs with water-soluble MSG, are carried out successfully by IPTC.

The Impact of Biosurfactants on Microbial Cell Properties Leading to Hydrocarbon Bioavailability Increase

The environment pollution with hydrophobic hydrocarbons is a serious problem that requires development of efficient strategies that would lead to bioremediation of contaminated areas. One of the common methods used for enhancement of biodegradation of pollutants is the addition of biosurfactants. Several mechanisms have been postulated as responsible for hydrocarbons bioavailability enhancement with biosurfactants. They include solubilization and desorption of pollutants as well as modification of bacteria cell surface properties. The presented review contains a wide discussion of these mechanisms in the context of alteration of bioremediation efficiency with biosurfactants. It brings new light to such a complex and important issue.

Saturation effect and transmembrane conversion of Monascus pigment in nonionic surfactant aqueous solution

Extractive fermentation in a nonionic surfactant aqueous solution provides a promising and efficient method to produce Monascus pigments. The behaviour of pigment secretion during the extractive cultivation was investigated in the present work. The results revealed that the secretion of intracellular pigment was limited by its saturation concentration in the nonionic surfactant aqueous solution. The intracellular pigment was completely extracted to the outside of the cell at a low cell density and high concentration of Triton X-100 (TX) in fermentation broth; otherwise, a restriction for pigment extraction would occur. The decrement of the intracellular orange and yellow pigments was inconsistent with the increment of extracellular pigments with an increase in the TX concentration. It could be inferred that the intracellular orange pigment was converted to extracellular yellow pigment during the transmembrane secretion process, which might be attributed to the enzyme catalysis in the non-aqueous phase solution. This study helps explain the mechanism of variation of pigment characteristic and extraction capacity in extractive fermentation.

Production of Monascus pigments as extracellular crystals by cell suspension culture

It is generally accepted that Monascus pigments are predominantly cell-bound, including both intracellular and surface-bound pigments. This long-term misconception was corrected in the present work. Production of extracellular crystal pigments by submerged culture of Monascus sp. was confirmed by microscopic observation and collection of Monascus pigments from extracellular broth by direct membrane filtration. Following up the new fact, the bioactivity of mycelia as whole-cell biocatalyst for biosynthesis and biodegradation of Monascus pigments had been detailedly examined in both an aqueous solution and a nonionic surfactant micelle aqueous solution. Based on those experimental results, cell suspension culture in an aqueous medium was developed as a novel strategy for accumulation of high concentration of Monascus pigments. Thus, glucose feeding during submerged culture in the aqueous medium was carried out successfully and high orange Monascus pigments concentration of near 4 g/L was achieved.

Effect of natural and synthetic surfactants on crude oil biodegradation by indigenous strains

Hydrocarbon pollution is a worldwide problem. In this study, five surfactants containing SDS, LAS, Brij 30, Tween 80 and biosurfactant were used to evaluate their effect on crude oil biodegradation. Hydrocarbon degrading bacteria were isolated from oil production water. The biosurfactant used was a kind of cyclic lipopeptide produced by Bacillus subtilis strain WU-3. Solubilization test showed all the surfactants could apparently increase the water solubility of crude oil. The microbial adhesion to the hydrocarbon (MATH) test showed surfactants could change cell surface hydrophobicity (CSH) of microbiota, depending on their species and concentrations. Microcalorimetric experiments revealed these surfactants exhibited toxicity to microorganisms at high concentrations (above 1 CMC), except for SDS which showed low antibacterial activity. Surfactant supplementation (about 0.1 and 0.2 CMC) could improve degradation rate of crude oil slightly, while high surfactant concentration (above 1 CMC) may decrease the degradation rate from 50.5% to 28.9%. Those findings of this work could provide guidance for the application of surfactants in bioremediation of oil pollution.

Extractive biodegradation and bioavailability assessment of phenanthrene in the cloud point system by Sphingomonas polyaromaticivorans

The biological treatment of polycyclic aromatic hydrocarbons is an important issue. Most microbes have limited practical applications because of the poor bioavailability of polycyclic aromatic hydrocarbons. In this study, the extractive biodegradation of phenanthrene by Sphingomonas polyaromaticivorans was conducted by introducing the cloud point system. The cloud point system is composed of a mixture of (40 g/L) Brij 30 and Tergitol TMN-3, which are nonionic surfactants, in equal proportions. After phenanthrene degradation, a higher wet cell weight and lower phenanthrene residue were obtained in the cloud point system than that in the control system. According to the results of high-performance liquid chromatography, the residual phenanthrene preferred to partition from the dilute phase into the coacervate phase. The concentration of residual phenanthrene in the dilute phase (below 0.001 mg/L) is lower than its solubility in water (1.18 mg/L) after extractive biodegradation. Therefore, dilute phase detoxification was achieved, thus indicating that the dilute phase could be discharged without causing phenanthrene pollution. Bioavailability was assessed by introducing the apparent logP in the cloud point system. Apparent logP decreased significantly, thus indicating that the bioavailability of phenanthrene increased remarkably in the system. This study provides a potential application of biological treatment in water and soil contaminated by phenanthrene.

The influence of bioaugmentation and biosurfactant addition on bioremediation efficiency of diesel-oil contaminated soil: feasibility during field studies

The study focused on assessing the influence of bioaugmentation and addition of rhamnolipids on diesel oil biodegradation efficiency during field studies. Initial laboratory studies (measurement of emitted CO2 and dehydrogenase activity) were carried out in order to select the consortium for bioaugmentation as well as to evaluate the most appropriate concentration of rhamnolipids. The selected consortium consisted of following bacterial taxa: Aeromonas hydrophila, Alcaligenes xylosoxidans, Gordonia sp., Pseudomonas fluorescens, Pseudomonas putida, Rhodococcus equi, Stenotrophomonas maltophilia, Xanthomonas sp. It was established that the application of rhamnolipids at 150 mg/kg of soil was most appropriate in terms of dehydrogenase activity. Based on the obtained results, four treatment methods were designed and tested during 365 days of field studies: I) natural attenuation; II) addition of rhamnolipids; III) bioaugmentation; IV) bioaugmentation and addition of rhamnolipids. It was observed that bioaugmentation contributed to the highest diesel oil biodegradation efficiency, whereas the addition of rhamnolipids did not notably influence the treatment process.

Solubilization of phenanthrene above cloud point of Brij 30: a new application in biodegradation

In the present study a new application of solubilization of phenanthrene above cloud point of Brij 30 in biodegradation was developed. It was shown that a temporal solubilization of phenanthrene above cloud point of Brij 30 (5wt%) permitted to obtain a stable increase of the solubility of phenanthrene even when the temperature was decreased to culture conditions of used microorganism Pseudomonas putida (28°C). A higher initial concentration of soluble phenanthrene was obtained after the cloud point treatment: 200 against 120μM without treatment. All soluble phenanthrene was metabolized and a higher final concentration of its major metabolite - 1-hydroxy-2-naphthoic acid - (160 against 85μM) was measured in the culture medium in the case of a preliminary cloud point treatment. Therefore a temporary solubilization at cloud point might have a perspective application in the enhancement of biodegradation of polycyclic aromatic hydrocarbons.

Solubilization capacity of nonionic surfactant micelles exhibiting strong influence on export of intracellular pigments in Monascus fermentation

In this study, perstractive fermentation of intracellular Monascus pigments in nonionic surfactant micelle aqueous solution had been studied. The permeability of cell membrane modified by nonionic surfactant might have influence on the rate of export of intracellular pigments into its extracellular broth while nearly no effect on the final extracellular pigment concentration. However, the solubilization of pigments in nonionic surfactant micelles strongly affected the final extracellular pigment concentration. The solubilization capacity of micelles depended on the kind of nonionic surfactant, the super-molecule assembly structure of nonionic surfactant in an aqueous solution, and the nonionic surfactant concentration. Elimination of pigment degradation by export of intracellular Monascus pigments and solubilizing them into nonionic surfactant micelles was also confirmed experimentally. Thus, nonionic surfactant micelle aqueous solution is potential for replacement of organic solvent for perstractive fermentation of intracellular product.

A novel actinomycete derived from wheat heads degrades deoxynivalenol in the grain of wheat and barley affected by Fusarium head blight

Deoxynivalenol (DON) is a hazardous and globally prevalent mycotoxin in cereals. It commonly accumulates in the grain of wheat, barley and other small grain cereals affected by Fusarium head blight (caused by several Fusarium species). The concept of reducing DON in naturally contaminated grain of wheat or barley using a DON-degrading bacterium is promising but has not been accomplished. In this study, we isolated a novel DON-utilising actinomycete, Marmoricola sp. strain MIM116, from wheat heads through a novel isolation procedure including an in situ plant enrichment step. Strain MIM116 had background degradation activity, and the activity was enhanced twofold by the consumption of DON. Among Tween 20, Triton X-100 and Tween 80, we selected Tween 80 as a spreading agent of strain MIM116 because it promoted DON degradation and the growth of strain MIM116 in the presence of DON. The inoculation of MIM116 cell suspension plus 0.01% Tween 80 into 1,000 harvested kernels of wheat and barley resulted in a DON decrease from approximately 3 mg kg(-1) to less than 1 mg kg(-1) of dry kernels, even when cells had only basal levels of DON-degrading activity. To the best of our knowledge, this is the first report that describes (1) the isolation of a DON-degrading bacterium from wheat heads, (2) the effects of surfactants on the biodegradation of DON and (3) the decrease of DON levels in naturally contaminated wheat and barley grain using a DON-degrading bacterium.

Why do microorganisms produce rhamnolipids?

We review the environmental role of rhamnolipids in terms of microbial life and activity. A large number of previous research supports the idea that these glycolipids mediate the uptake of hydrophobic substrates by bacterial cells. This feature might be of highest priority for bioremediation of spilled hydrocarbons. However, current evidence confirms that rhamnolipids primarily play a role in surface-associated modes of bacterial motility and are involved in biofilm development. This might be an explanation why no direct pattern of hydrocarbon degradation was often observed after rhamnolipids supplementation. This review gives insight into the current state of knowledge on how rhamnolipids operate in the microbial world.

Utilization of Triton X-100 and polyethylene glycols during surfactant-mediated biodegradation of diesel fuel

The hypothesis regarding preferential biodegradation of surfactants applied for enhancement of microbial hydrocarbons degradation was studied. At first the microbial degradation of sole Triton X-100 by soil isolated hydrocarbon degrading bacterial consortium was confirmed under both full and limited aeration with nitrate as an electron acceptor. Triton X-100 (600 mg/l) was utilized twice as fast for aerobic conditions (t(1/2)=10.3h), compared to anaerobic conditions (t(1/2)=21.8h). HPLC/ESI-MS analysis revealed the preferential biodegradation trends in both components classes of commercial Triton X-100 (alkylphenol ethoxylates) as well as polyethylene glycols. The obtained results suggest that the observed changes in the degree of ethoxylation for polyethylene glycol homologues occurred as a consequence of the 'central fission' mechanism during Triton X-100 biodegradation. Subsequent experiments with Triton X-100 at approx. CMC concentration (150 mg/l) and diesel oil supported our initial hypothesis that the surfactant would become the preferred carbon source even for hydrocarbon degrading bacteria. Regardless of aeration regimes Triton X-100 was utilized within 48-72 h. Efficiency of diesel oil degradation was decreased in the presence of surfactant for aerobic conditions by approx. 25% reaching 60 instead of 80% noted for experiments without surfactant. No surfactant influence was observed for anaerobic conditions.