Lipase production and purification by self-buffering ionic liquid-based aqueous biphasic systems

n this work, a group of Good’s buffer ionic liquids (GB-ILs) comprised of tetrabutylammonium, tetra- butylphosphonium and cholinium cations paired with Good’s buffer (GB) anions (MOPSO, BES and TAPSO) was studied. Their distinctive capability to induce the formation of aqueous biphasic systems (ABS) with the salts K3PO4, K2CO3, and (NH4)2SO4, and the polymers poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG), and PEG-PPG copolymers was demonstrated. Their application as purification tools to recover a lipase produced via submerged fermentation by Burkholderia cepacia ST8 was investigated. The lipase was preferentially partitioned towards the GB-IL-rich phase in both the GB-IL + salt and polymer + GB-IL purification systems. Molecular docking studies were performed aiming at to understand the possible interactions between the GB-IL ions and the lipase residues. Furthermore, the selected GB-IL-based ABS was investigated as part of an integrated process developed to successfully recover and purify an extracellular B. cepacia ST8 lipase from the fermentation broth, in which a purification factor of 22.4 ± 0.7 and a recovery yield of (94.0 ± 0.2) % were achieved.publishe

Evaluating Self-buffering Ionic Liquids for Biotechnological Applications

A new range of Good’s buffer ionic liquids (GB-ILs), displaying simultaneously the properties of ionic liquids and Good’s buffers, were synthesized by combination of Good’s buffers anions (MOPSO, BES, TAPSO and CAPSO) and tetrabutylammonium, tetrabutylphosphonium and cholinium cations via an acid-base neutralization reaction. The activity and stability of a lipolytic enzyme from Pseudomonas cepacia in aqueous solutions of these buffers were evaluated and the results show their advantage as media for enzymatic reactions when compared to conventional phosphate buffers. Moreover aqueous biphasic systems (ABS) composed by these GB-ILs and potassium citrate were investigated and shown to be highly effective and selective for the partitioning of the lipolytic enzyme into the GB-IL-rich phase. The results allow the development of an efficient and biocompatible process combining the self-buffering and enzyme-stabilizing properties of the GB-ILs in the reaction step, with the advantages of GB-ILs as extraction solvents in ABS

Phase Behavior and Molecular Dynamics Simulation Studies of New Aqueous Two-Phase Separation Systems Induced by HEPES Buffer

Here, for the first time, we show that with addition of a biological buffer, 4-(2-hydroxyethyl)­piperazine-1-ethanesulfonic acid (HEPES), into aqueous solutions of tetrahydrofuran (THF), 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, <i>tert</i>-butanol, acetonitrile, or acetone, the organic solvent can be excluded from water to form a new liquid phase. The phase diagrams have been determined at ambient temperature. In order to understand why and how a zwitterion solute (HEPES) induced phase separation of the investigated systems, molecular dynamics (MD) simulation studies are performed for HEPES + water + THF system. The MD simulations were conducted for the aqueous mixtures with 12 different compositions. The reliability of the simulation results of HEPES in pure water and beyond the phase separation mixtures was justified by comparing the densities obtained from MD with the experimental values. The simulation results of HEPES in pure THF and in a composition inside the phase separation region were justified qualitatively. Interestingly, all HEPES molecules entirely aggregated in pure THF. This reveals that HEPES is insoluble in pure THF, which is consistent with the experimental results. Even more interestingly, the MD simulation for the mixture with composition inside the phase separation region showed the formation of two phases. The THF molecules are squeezed out from the water network into a new liquid phase. The hydrogen bonds (HBs), HB lifetime, HB Gibbs energy (Δ<i>G</i>), radial distribution functions (RDFs), coordination numbers (CNs), electrostatic interactions, and the van der Waals interactions between the different species have been analyzed. Further, MD simulations for the other phase separation systems by choosing a composition inside the two liquids region for each system were also simulated. Our findings will therefore pave the way for designing new benign separation auxiliary agents

Phase Equilibria of the Ternary System of Lithium Sulfate + Polyethylene Glycol (PEG3000) + Water at Different pH: Experiment Determination, Correlation, and Thermodynamic Modeling

The phase equilibrium data for the ternary systems [lithium sulfate (Li2SO4) + polyethylene glycol (PEG3000) + water] were measured at 298.15 K and at various pH values (2.94, 4.90, and 6.80). The solid–liquid equilibrium data including the solubility, density, and refractive index were determined using the isothermal dissolution equilibrium method. The liquid–liquid equilibrium (LLE) data for the aqueous two-phase system were obtained experimentally by measuring the biphasic physical properties, including the density and refractive index at 298.15 K. Subsequently, the binodal curves were correlated by using the Pirdashti and Merchuk equations, the effective excluded volumes were calculated from the binodal curve data, and the tie-line compositions were adjusted to the Othmer–Tobias and Bancroft equations, respectively. Results show that the solubility of Li2SO4 in the aqueous polymeric solution mitigates as the content of PEG increases, eventually. It was found that the more acidic solution induces the salting-out effect, and the LLE formed easily at the lower pH of studied systems. Finally, the extended UNIQUAC, the modified UNIQUAC-FV, and the modified UNIFAC-NRF models were selected to correlate the LLE data of the studied systems, and the modified UNIQUAC-FV model gives a better correlation for tie-lines data

Densities, viscosities, and refractive indexes of Good's buffer ionic liquids

Good’s buffer ionic liquids (GB-ILs) have demonstrated their potential usefulness in the biotechnological field due to their advantageous properties of self-buffering and biocompatibility. To further investigate the applicability of these solvents in industrial process, the knowledge of the thermophysical properties of such solvents is of utmost importance. In this work, a series of GB-ILs prepared by the combination of the Good’s buffer anions MOPSO, BES, TAPSO, and CAPSO, with tetrabutylammonium, tetrabutylphosphonium, and cholinium cations were synthesized and characterized regarding the determination of the melting and decomposition temperatures. Additionally, the physical properties such as density, viscosity and refractive index were measured for these GB-ILs at atmospheric pressure and in the (288.15 to 353.15) K temperature range. Additional properties such as the isobaric thermal expansion coefficient and activation energy for viscous flow were also further derived from the temperature dependence of the measured properties. The effects of cation and anion species of GB-ILs on these thermophysical properties are discussed

Aerated Static Pile Composting for Industrial Biowastes: From Engineering to Microbiology

This work demonstrated the feasibility of an industrial-scale aerated static pile composting system for treating one of the common biowastes—soybean curd residue. The mixing ratios of the feedstock were optimized to achieve a carbon–nitrogen ratio and a moisture level in the ranges of 25–35 and 60–70%, respectively. This open-air composting system required 6–7 months to obtain a mature compost. Solvita and seed germination tests further confirmed the maturity of the compost, with 25% compost extract concentration yielding the best germination index in the absence of phytotoxicity. The bacterial and fungal compositions of the compost piles were further examined with metagenomic analysis. Thermoactinomyces spp., Oceanobacillus spp., and Kroppenstedtia spp. were among the unique bacteria found, and Diutina rugosa, Thermomyces dupontii, and Candida taylorii were among the unique fungi found in the compost piles, suggesting the presence of good microorganisms for degrading the organic biowastes

Densities, Viscosities, and Refractive Indexes of Good’s Buffer Ionic Liquids

Good’s buffer ionic liquids (GB-ILs) have demonstrated their potential usefulness in the biotechnological field due to their advantageous properties of self-buffering and biocompatibility. To further investigate the applicability of these solvents in industrial process, the knowledge of the thermophysical properties of such solvents is of utmost importance. In this work, a series of GB-ILs prepared by the combination of the Good’s buffer anions MOPSO, BES, TAPSO, and CAPSO, with tetrabutylammonium, tetrabutylphosphonium, and cholinium cations were synthesized and characterized regarding the determination of the melting and decomposition temperatures. Additionally, the physical properties such as density, viscosity and refractive index were measured for these GB-ILs at atmospheric pressure and in the (288.15 to 353.15) K temperature range. Additional properties such as the isobaric thermal expansion coefficient and activation energy for viscous flow were also further derived from the temperature dependence of the measured properties. The effects of cation and anion species of GB-ILs on these thermophysical properties are discussed

Surface Coating Effect on Corrosion Resistance of Titanium Alloy Bone Implants by Anodizing Method

In the presented work, the formation of anodic oxide film on Ti-6Al-4V ELI (Extra Low Interstitial) alloy in 0.02 M trisodium phosphate (Na3PO4) electrolyte solution using various voltages were investigated. The color produced by the anodizing, the intensity of TiO2 content, the thickness of the oxide layer, and the corrosion rate were examined. It was obtained that the color appearance of Ti-6Al-4V ELI could be changed easily by altering the applied voltages. The higher the voltage applied in the anodizing process, the thicker the titanium oxide layer formed. The corrosion resistance analysis in a Simulated Body Fluid revealed that the non-anodized specimen showed a higher corrosion rate compared to the anodized specimen. The increase of oxide layer thickness leads to a significant decrease in corrosion rate and consequently increases the corrosion resistance. In addition, the anodized sample achieved the highest corrosion resistance at 15 V