The potential of cloud point system as a novel two-phase partitioning system for biotransformation

Using coarse-grained molecular dynamics to understand the effect of ionic liquids on the aggregation of Pluronic copolymer solutions

This study is aimed to enhance the understanding of the interaction between ionic liquids (ILs) and non-ionic Pluronic triblock copolymers in aqueous two-phase micellar systems (ATPMS) used for the selective separation/purification of hydrophobic biomolecules. The ILs allow a precise control of the cloud point phase separation temperature (CPT), particularly important when the stability of the molecule is highly dependent on temperature. The effect of choline-based ILs, with two different counter-anions, chloride and hexanoate, was evaluated using molecular dynamics simulations (MD) for F-68 and L-35 Pluronic aqueous solutions. The simulations revealed the role played by the anions during the Pluronic self-assembly, with choline chloride hindering Pluronic aggregation and the choline hexanoate favouring micelle formation and coalescence, in agreement with the experimental data. A detailed study of the accessible surface area of Pluronic showed a progressive dehydration of the Pluronic hydrophilic micelle corona in choline hexanoate mixtures promoting inter-micelle interactions and, consequently, micelle coalescence. With the addition of choline hexanoate, it was observed that the hydrophilic segments, which form the micelle corona, twisted towards the Pluronic micelle core. The electrostatic interaction is also shown to play a key role in this IL-Pluronic aqueous solution, as the hexanoate anions are accommodated in the Pluronic micelle core, while the choline cations are hosted by the Pluronic micelle corona, with the ions interacting with each other during the self-assembly process. In addition, a comparison study of F-68 and L-35 aqueous solutions shows that the IL impact depends on the length of the Pluronic hydrophilic segment. This work provides a realistic microscopic scenario of the complex interactions between Pluronic copolymers and ILs.

Improving Product Specificity of Whole-Cell Alkane Oxidation in Nonconventional Media: A Multivariate Analysis Approach

Two-liquid-phase reaction media have long been used in bioconversions to supply or remove hydrophobic organic reaction substrates and products to reduce inhibitory and toxic effects on biocatalysts. In case of the terminal oxyfunctionalization of linear alkanes by the AlkBGT monooxygenase the excess alkane substrate is often used as a second phase to extract the alcohol, aldehyde, and acid products. However, the selection of other carrier phases or surfactants is complex due to a large number of parameters that are involved, such as biocompatibility, substrate bioavailability, and product extraction selectivity. This study combines systematic high-throughput screening with chemometrics to correlate physicochemical parameters of a range of cosolvents to product specificity and yield using a multivariate regression model. Partial least-squares regression shows that the defining factor for product specificity is the solubility properties of the reaction substrate and product in the cosolvent, as measured by Hansen solubility parameters. Thus the polarity of cosolvents determines the accumulation of either alcohol or acid products. Whereas usually the acid product accumulates during the reaction, by choosing a more polar cosolvent the 1-alcohol product can be accumulated. Especially with Tergitol as a cosolvent, a 3.2-fold improvement in the 1-octanol yield to 18.3  mmol  L^-1 is achieved relative to the control reaction without cosolvents.

Application of Micellar Extraction for Isolation of Famotidine from Aqueous Samples Prior to its Chromatographic Determination

Micellar extraction was applied to isolate famotidine from aqueous samples. This drug is an H₂ receptor antagonist used for the treatment of stomach diseases. The process was performed with a mixture of anionic sodium dodecylsulfate and nonionic Triton X-114 surfactants. The effect of different parameters on the efficiency of the micellar extraction such as electrolyte and surfactant concentration, pH of sample, temperature, shaking and centrifugation time was investigated. The influence of foreign substances on a studied process was tested. The elaborated procedure was applied for HPLC–UV determination of famotidine in natural water samples. The calibration graph was recorded in the range 1.35–37.12 μg mL⁻¹ of the studied compound. The repeatability of the method was equal to 7.4%. The limit of detection and quantification values for the determination of famotidine by using the proposed method amounted to 0.40 and 1.25 μg mL⁻¹, respectively.

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.

Perstraction of Intracellular Pigments through Submerged Fermentation of Talaromyces spp. in a Surfactant Rich Media: A Novel Approach for Enhanced Pigment Recovery

A high percentage of the pigments produced by Talaromyces spp. remains inside the cell, which could lead to a high product concentration inhibition. To overcome this issue an extractive fermentation process, perstraction, was suggested, which involves the extraction of the intracellular products out of the cell by using a two-phase system during the fermentation. The present work studied the effect of various surfactants on secretion of intracellular pigments produced by Talaromyces spp. in submerged fermentation. Surfactants used were: non-ionic surfactants (Tween 80, Span 20 and Triton X-100) and a polyethylene glycerol polymer 8000, at different concentrations (5, 20, 35 g/L). The highest extracellular pigment yield (16 OD500nm) was reached using Triton X-100 (35 g/L), which was 44% higher than the control (no surfactant added). The effect of addition time of the selected surfactant was further studied. The highest extracellular pigment concentration (22 OD500nm) was achieved when the surfactant was added at 120 h of fermentation. Kinetics of extracellular and intracellular pigments were examined. Total pigment at the end of the fermentation using Triton X-100 was 27.7% higher than the control, confirming that the use of surfactants partially alleviated the product inhibition during the pigment production culture.

Bioconversion of AHX to AOH by resting cells of Burkholderia contaminans CH-1

Fairy rings are zones of stimulated grass growth owing to the interaction between a fungus and a plant. We previously reported the discovery of two novel plant-growth regulating compounds related to forming fairy rings, 2-azahypoxanthine (AHX) and 2-aza-8-oxohypoxanthine (AOH). In this study, a bacterial strain CH-1 was isolated from an airborne-contaminated nutrient medium containing AHX. The strain converted AHX to AOH and identified as Burkholderia contaminans based on the gene sequence of its 16S rDNA. The quantitative production of AOH by resting cells of the strain was achieved. Among seven Burkholderia species, two bacteria and two yeasts tested, B. contaminans CH-1 showed the highest rate of conversion of AHX to AOH. By batch system, up to 10.6 mmol AHX was converted to AOH using the resting cells. The yield of this process reached at 91%.

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.

Sphingolipids and plant defense/disease: the "death" connection and beyond

Sphingolipids comprise a major class of structural materials and lipid signaling molecules in all eukaryotic cells. Over the past two decades, there has been a phenomenal growth in the study of sphingolipids (i.e., sphingobiology) at an average rate of ∼1000 research articles per year. Sphingolipid studies in plants, though accounting for only a small fraction (∼6%) of the total number of publications, have also enjoyed proportionally rapid growth in the past decade. Concomitant with the growth of sphingobiology, there has also been tremendous progress in our understanding of the molecular mechanisms of plant innate immunity. In this review, we (i) cross examine and analyze the major findings that establish and strengthen the intimate connections between sphingolipid metabolism and plant programmed cell death (PCD) associated with plant defense or disease; (ii) highlight and compare key bioactive sphingolipids involved in the regulation of plant PCD and possibly defense; (iii) discuss the potential role of sphingolipids in polarized membrane/protein trafficking and formation of lipid rafts as subdomains of cell membranes in relation to plant defense; and (iv) where possible, attempt to identify potential parallels for immunity-related mechanisms involving sphingolipids across kingdoms.

Fractal kinetic analysis of the enzymatic saccharification of cellulose under different conditions

Fractal kinetic analysis has been applied for the kinetics of enzymatic saccharification of cellulose. Based on the first order cellulose degradation kinetic, a fractal kinetic model with two parameters (rate coefficient and fractal exponent) has been developed. The model fits very well with the experimental data of enzymatic saccharification of cellulose under different conditions, including cellulase loading, nature of substrate, hydrolysis temperature, and addition of nonionic surfactant or polymer in the reaction medium. It indicates that the complex kinetics of enzymatic saccharification of cellulose can be described with the fractal kinetic model. The model exhibits that an addition of nonionic surfactant or polymer increases the rate coefficient and decreases the fractal exponent at the same time. A nonionic surfactant or polymer aqueous solution may be a potential medium engineering method for enzymatic saccharification of cellulose in biofuel industry.

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.

Cloud point of nonionic surfactant Triton X-45 in aqueous solution

Triton X-45, a nonionic surfactant with a low hydrophile-lypophile balance value and dispersible in aqueous solution at room temperature, has a Krafft point above the room temperature. The cloud point of Triton X-45 in an aqueous solution is different from the conventional aqueous nonionic surfactant micelle solution. It was further confirmed by a determination of the effect of additives on the phase behavior of aqueous solutions containing Triton X-45. The experimental fact eliminates the prevalent concept that the cloud point of Triton X-45 is below room temperature, which is helpful to exploit a biocompatible medium for a microbial growth and then for whole cell microbial transformation in a nonaqueous medium.