Álvaro Silva Lima

Ionic liquids as adjuvants for the tailored extraction of biomolecules in aqueous biphasic systems

The potential use of ionic liquids (ILs) as adjuvants in typical polymer-salt aqueous systems for the separation and purification of vital biomolecules is investigated. An innovative study involving the addition of various imidazolium-based ILs to conventional PEG/inorganic salt aqueous biphasic systems (ABS), aiming at controlling their phase behaviour and extraction capability for L-tryptophan, is carried out here. For this purpose, phase diagrams and respective tie-lines for PEG 600/Na2SO4 ABS with the addition of small quantities of IL were established. In addition, the partition coefficients of L-tryptophan were determined in those systems. The results obtained indicate that the addition of small amounts of IL to the typical PEG/inorganic salt aqueous systems could largely control the extraction efficiency for L-tryptophan, and that efficiency depends on the IL employed. Salting-in inducing ILs enhance the partition coefficient of L-tryptophan for the PEG-rich phase while salting-out inducing ILs decrease the partitioning of the amino acid. These results are an interesting advance in biotechnological separation processes regarding the extraction of biomolecules that could be used instead of the common approach of PEG functionalization.

Production and purification of an extracellular lipolytic enzyme using ionic liquid-based aqueous two-phase systems

The ability of ionic liquid-based aqueous two-phase systems (ATPS) to purify lipase produced by fermentation is here evaluated and compared against conventional PEG-based ATPS systems. Four ionic liquids, chosen after screening of a larger number of ionic liquids are evaluated, with the maximum purification and higher recovery being obtained for the systems based on [C8mim]Cl. It is shown that IL-based ATPS have a performance superior to PEG-based ATPS for the purification of this enzyme.

Design of ionic liquids for lipase purification.

Aqueous two-phase systems (ATPS) are considered as efficient downstream processing techniques in the production and purification of enzymes, since they can be considered harmless to biomolecules due to their high water content and due to the possibility of maintaining a neutral pH value in the medium. A recent type of alternative ATPS is based on hydrophilic ionic liquids (ILs) and salting-out inducing salts. The aim of this work was to study the lipase (Candida antarctica lipase B - CaLB) partitioning in several ATPS composed of ionic liquids (ILs) and inorganic salts, and to identify the best IL for the enzyme purification. For that purpose a wide range of IL cations and anions, and some of their combinations were studied. For each system the enzyme partitioning between the two phases was measured and the purification factors and enzyme recoveries were determined. The results indicate that the lipase maximum purification and recovery were obtained for cations with a C(8) side alkyl chain, the [N(CN)(2)] anion and ILs belonging to the pyridinium family. However, the highest purification parameters were observed for 1-methyl-3-octylimidazolium chloride [C(8)mim]Cl, suggesting that the IL extraction capability does not result from a cumulative character of the individual characteristics of ILs. The results indicate that the IL based ATPS have an improved performance in the lipase purification and recovery.

Purification of lipase produced by a new source of Bacillus in submerged fermentation using an aqueous two-phase system

This work discusses the application of an aqueous two-phase system for the purification of lipases produced by Bacillus sp. ITP-001 using polyethylene glycol (PEG) and potassium phosphate. In the first step, the protein content was precipitated with ammonium sulphate (80% saturation). The enzyme remained in the aqueous solution and was dialyzed against ultra-pure water for 18 h and used to prepare an aqueous two-phase system (PEG/potassium phosphate). The use of different molecular weights of PEG to purify the lipase was investigated; the best purification factor (PF) was obtained using PEG 20,000g/mol, however PEG 8000 was used in the next tests due to lower viscosity. The influence of PEG and potassium phosphate concentrations on the enzyme purification was then studied: the highest FP was obtained with 20% of PEG and 18% of potassium phosphate. NaCl was added to increase the hydrophobicity between the phases, and also increased the purification factor. The pH value and temperature affected the enzyme partitioning, with the best purifying conditions achieved at pH 6.0 and 4°C. The molecular mass of the purified enzyme was determined to be approximately 54 kDa by SDS-PAGE. According to the results the best combination for purifying the enzyme is PEG 8000g/mol and potassium phosphate (20/18%) with 6% of NaCl at pH 6.0 and 4°C (201.53 fold). The partitioning process of lipase is governed by the entropy contribution.

Partitioning of pectinolytic enzymes in polyethylene glycol/potassium phosphate aqueous two-phase systems

Abstract Four different pectinolytic enzymes have been partitioned in polyethylene glycol (PEG)-potassium phosphate aqueous two-phase systems (20–15%). The influence of PEG molecular weight and the addition of sodium chloride were investigated. The best results concerning to the partition coefficients (Kp and Ke) and the yield recovery (R) were: PEG-400/phosphate with NaCl for exo-polygalacturonase (Ke=5.35 and R=89.5%), PEG-600/phosphate for pectin lyase (PL) (Ke=43.18 and R=98.5%) and pectinesterase (PE) (Ke=1.51 and R=69.6%), and PEG-10,000/phosphate for endo-polygalacturonase (Ke=1.35 and R=53.5%). The best purification factors were observed in the upper phase for the systems containing high molecular weight PEG without NaCl: PEG-6000 for exo-polygalacturonase (5.49 fold) and PEG-10,000 for endo-polygalacturonase (16.28 fold), PE (16.64 fold) and PL (14.27 fold).

Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzymes activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with protic ionic liquids also favoured reduced mass loss according to TG curves (always less than 42.9%) when compared to the immobilized matrix without protic ionic liquids (45.1%), except for the sample containing 3.0% protic ionic liquids (46.5%), verified by thermogravimetric analysis. Ionic liquids containing a more hydrophobic alkyl group in the cationic moiety were beneficial for recovery of the activity of the immobilized lipase. The physico-chemical characterization confirmed the presence of the enzyme and its immobilized derivatives obtained in this study by identifying the presence of amino groups, and profiling enthalpy changes of mass loss.

Lipase purification using ionic liquids as adjuvants in aqueous two-phase systems

Aqueous two-phase systems (ATPS) are efficient, environmentally friendly, and “biocompatible” separation processes, which allow the recovery of enzymes. The most common systems are based on polymers and salts, and recently, to overcome the low polarity difference between the phases of the polymeric systems, ATPS based on ionic liquids (ILs) were proposed and have been successfully applied in this field. This work discusses the use of imidazolium-based ILs not as phase forming compounds but as adjuvants (5 wt%) in ATPS of polyethylene glycol systems (1500, 4000, 6000 and 8000 g mol−1) with potassium phosphate buffer at pH 7, in the extraction and purification of a lipase produced by submerged fermentation by Bacillus sp. ITP-001. An initial optimization study was carried out with the commercial lipase B from Candida antarctica (CaLB) allowing us to further purify the commercial CaLB (purification factor = 5.2). Using the optimized conditions, a purification factor of 245 for the lipase from Bacillus sp. ITP-001 was achieved with 1-hexyl-3-methyl imidazolium chloride. The high purification factor is a consequence of the favorable interactions between the IL and the contaminant proteins that migrate for the PEG-rich phase, where the IL also concentrates preferentially, while the enzyme remains in the salt-rich phase.

Increased significance of food wastes: Selective recovery of added-value compounds

A single-step selective separation of two food additives was investigated using alcohol-salt aqueous two-phase systems (ATPS). The selective partitioning of two of the most used additives from a processed food waste material, vanillin and l-ascorbic acid, was successfully accomplished. The results obtained prove that alcohol-salt ATPS can be easily applied as cheaper processes for the selective recovery of valuable chemical products from food wastes and other sources. As a first approach, the phase diagrams of ATPS composed of different alcohol+inorganic salt+water were determined at 298 (± 1)K and atmospheric pressure. The influence of methanol, ethanol, 1-propanol, and 2-propanol and K(3)PO(4), K(2)HPO(4) or KH(2)PO(4)/K(2)HPO(4) in the design of the phase diagrams was addressed. After the evaluation of the phase diagrams behaviour, the influence of the phase forming constituents was assessed towards the partition coefficients and recovery percentages of vanillin and l-ascorbic acid among the coexisting phases. Both model systems and real processed food waste materials were employed. Using these ATPS as partitioning systems it is possible to recover and separate vanillin, which migrates for the alcohol-rich phase, from l-ascorbic acid, which preferentially partitions for the salt-rich phase.

Enhanced extraction of bovine serum albumin with aqueous biphasic systems of phosphonium- and ammonium-based ionic liquids

Novel aqueous biphasic systems (ABS) composed of phosphonium- or ammonium-based ionic liquids (ILs), combined with a buffered aqueous solution of potassium citrate/citric acid (pH=7.0), were investigated for the extraction of proteins. For that purpose, the phase diagrams, tie-lines and tie-line lengths were determined at 25 °C, and the performance of these ABS for the extraction of bovine serum albumin (BSA) was then evaluated. The obtained results reveal that, with the exception of the more hydrophobic ILs, most of the systems investigated allow the complete extraction of BSA for the IL-rich phase in a single-step. These remarkable extraction efficiencies are far superior to those afforded by more conventional extraction systems previously reported. The composition of the biphasic systems, i.e., the amount of phase-forming components, was also investigated aiming at reducing the overall costs of the process without losing efficiency on the protein extraction. It is shown that the extraction efficiencies of BSA are maintained at 100% up to high protein concentrations (at least up to 10 g L(-1)). The recovery of the BSA from the IL-rich phase by dialysis is also shown in addition to the demonstration of the IL recyclability and reusability, at least for 3 times. In the sequential three-step extractions (BSA recovery/IL reusability), the extraction efficiencies of BSA for the IL-rich phase were maintained at 100%. For the improved ABS, the preservation of the protein native conformation was confirmed by Size Exclusion High-Performance Liquid Chromatography (used also as the quantification method) and by Fourier Transform Infra-Red spectroscopy. According to the results herein reported, ABS composed of phosphonium- or ammonium-based ILs and a biodegradable organic salt represent an alternative and remarkable platform for the extraction of BSA and may be extended to other proteins of interest.

Aqueous biphasic systems composed of ionic liquids and sodium carbonate as enhanced routes for the extraction of tetracycline

Aqueous biphasic systems (ABS) using ionic liquids (ILs) offer an alternative approach for the extraction, recovery, and purification of biomolecules through their partitioning between two aqueous liquid phases. In this work, the ability of a wide range of ILs to form ABS with aqueous solutions of Na2CO3 was evaluated. The ABS formed by IL + water + Na2CO3 were determined at 25°C, and the respective solubility curves, tie‐lines, and tie‐line lengths are reported. The studied ILs share the common chloride anion, allowing the IL cation core, the cation isomerism, the presence of functionalized groups, and alkyl side chain length effects to be evaluated. An increase in the cation side alkyl chain length leads to a higher ability for liquid–liquid demixing whereas different positional isomers and the presence of an allyl group have no major influence in the phase diagrams behavior. Quaternary phosphonium‐ and ammonium‐based fluids are more able to form an ABS when compared with imidazolium‐, pyridinium‐, pyrrolidinium‐, and piperidium‐based ILs. Moreover, the presence of an aromatic cation core has no major contribution to the formation of ABS when compared to the respective nonaromatic counterparts. Finally, to appraise on the systems applicability in downstream processing, selected systems were used for the partitioning of tetracyclines (neutral and salt forms) — a class of antibiotics produced by bacteria fermentation. Single‐step extraction efficiencies for the IL‐rich phase were always higher than 99% and confirm the great potential of ILs to be applied in the biotechnological field.