Supported ionic liquid materials for L-asparaginase immobilization

L-asparaginase (ASNase) (L-asparagine amidohydrolase EC 3.5.1.1) has been widely used as a therapeutic agent in the treatment of acute lymphoblastic leukemia (ALL) and in the food industry for the removal of toxic acrylamide (formed in foods cooked at high temperatures). Accordingly, ASNase is also used in biosensors for leukemia diagnosis. To improve the performance of ASNase and overcome the limitations of free enzymes, namely low stability and biocatalytic activity, enzyme immobilization is one of the most used strategies. Several supports as carbon nanotubes, graphene and chitosan have been reported for ASNase immobilization. Among them, nanomaterials, and in particular silica, have emerged as a promising alternative support for enzyme immobilization due to their unique characteristics, such as biological compatibility and high surface to volume ratio, being thus identified as promising supports for ASNase. In this work, supported ionic liquid materials (SILs) based on silica were used as novel immobilization supports for ASNase by a simple adsorption method. Different experimental conditions, namely contact time, medium pH and ASNase/SILs ratio were evaluated. The performance of the immobilized enzyme was studied by measuring its activity through the monitoring of the hydrolysis of the substrate, Lasparagine. Characterization of the ASNase-SILs bioconjugate was carried out to evaluate the adsorption of the ASNase onto the supports. The immobilization of ASNase onto the SILs was successfully achieved with an activity of immobilized ASNase ranging from 0.6 to 0.86 U of enzyme per mg of SILs under the optimum immobilization conditions (60 min, pH 8.0 and 0.06 mg.mL-1 of ASNase in 10 mg of SILs).publishe

Pristine carbon nanotubes for an efficient L-asparaginase immobilization

The enzyme L-asparaginase (ASNase) presents effective antineoplastic properties for acute lymphoblastic leukemia treatment, besides their potential use in the food sector to decrease acrylamide formation. Considering their applications, the improvement of these enzyme properties by efficient immobilization techniques is in high demand. Carbon nanotubes are promising enzyme immobilization supports since these materials have increased surface area and effective capacity for enzyme loading. Accordingly, in this study, multi-walled carbon nanotubes (MWCNTs) were explored as novel supports for ASNase immobilization by a simple adsorption method. The effect of pH, the contact time of immobilization, and the ASNase to nanoparticles mass ratio were optimized according to the enzyme immobilization yield and relative recovered activity. The enzyme-MWCNTs bioconjugation was confirmed by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) studies. MWCNTs have a high ASNase loading capacity, with a maximum immobilization yield of 90%. The adsorbed ASNase retains 90% of the initial enzyme activity at the optimized conditions (pH 8, 60 min, and 1.5×10-3 g.mL-1 of ASNase). According to these results, ASNase immobilized onto MWCNTs can find in several areas improved applications, namely biosensors, medicine, and the food industry.publishe

Influence of salts on the coexistence curve and protein partitioning in nonionic aqueous two-phase micellar systems

Aqueous two-phase micellar systems (ATPMS) can be exploited in separation science for the extraction/purification of desired biomolecules. Prior to phase separation the surfactant solution reaches a cloud point temperature, which is influenced by the presence of electrolytes. In this work, we provide an investigation on the cloud point behavior of the nonionic surfactant C10E4 in the presence of NaCl, Li2SO4 and KI. We also investigated the salts' influence on a model protein partitioning. NaCl and Li2SO4 promoted a depression of the cloud point. The order of salts and the concentration that decreased the cloud point was: Li2SO4 0.5 M > NaCl 0.5 M ≈ Li2SO4 0.2 M. On the other hand, 0.5 M KI dislocated the curve to higher cloud point values. For our model protein, glucose-6-phosphate dehydrogenase (G6PD), partitioning experiments with 0.5 M NaCl or 0.2 M Li2SO4 at 13.85 °C showed similar results, with KG6PD ~ 0.46. The lowest partition coefficient was obtained in the presence of 0.5 M KI (KG6PD = 0.12), with major recovery of the enzyme in the micelle-dilute phase (%Recovery = 90%). Our results show that choosing the correct salt to add to ATPMS may be useful to attain the desired partitioning conditions at more extreme temperatures. Furthermore, this system can be effective to separate a target biomolecule from fermented broth contaminants.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Aqueous biphasic systems composed of cholinium chloride and polymers as effective platforms for the purification of recombinant green fluorescent protein

Green fluorescent protein (GFP) has excellent properties as a biosensor and biomarker; however, its widespread use is limited by its purification costs. Alternative low-cost purification techniques can overcome this issue. The aim of this work was to evaluate aqueous biphasic systems (ABS) composed of cholinium chloride ([Ch]Cl) and different polymers as effective platforms to recover GFP from cell lysate of recombinant Escherichia coli BL21. All systems completely extracted GFP from cell lysate (>99%) into the polymeric- or [Ch]Cl-rich phases. In general, [Ch]Clbased ABS allowed a good purification capacity (GFP 80− 100% pure), with the best results (approximately 100% pure GFP) achieved with a polypropylene glycol (PPG)-400/[Ch]Cl ABS in a single-step extraction or in a two-step extraction (backextraction) by the integration of a polyethylene glycol (PEG)/sodium polyacrylate+[Ch]Cl ABS with a following stage using a PEG/[Ch]Cl-based ABS. Additionally, to demonstrate the potential of the PPG-400/[Ch]Cl ABS in downstream processing, solvent recycling and GFP polishing were carried out using ultrafiltration. Finally, the capacity of the PPG-400/[Ch]Cl ABS to extract other fluorescent proteins was also confirmed. The results clearly demonstrated that the PPG-400/[Ch]Cl ABS can be applied in downstream processing for the purification of proteins, not only enhancing purification yields but also providing simpler, quicker, cost-effective, and biocompatible processes.publishe

Purification of green fluorescent protein using fast centrifugal partition chromatography

The green fluorescent protein (GFP) is a biomolecule used in many biological applications such as biomarkers and biosensors, which require high purity levels. It is usually obtained from recombinant Escherichia coli strains, which also produces other endogenous proteins, demanding multiple purification steps, and consequently, increasing the overall costs to obtain pure GFP. Simpler and cheaper purification methods like Aqueous Biphasic Systems (ABS) were already successfully applied to purify GFP at lab scale. Therefore, the development of automatized industrially compatible purification platforms, such as countercurrent chromatography using ABS, can potentially improve the GFP production. This work studied the continuous purification of the variant enhanced GFP (EGFP) by applying ABS composed of polyethylene glycol (PEG 8000), sodium polyacrylate (NaPA 8000) and sodium sulfate (Na2SO4) as electrolyte. An initial screening was carried by changing the electrolyte content in the ABS. The increase of this condition has demonstrated an increase on the EGFP partition for the PEG-rich phase. The most efficient ABS and, at the same time, with the most appropriate conditions, namely the system composed of 15 wt% PEG 8000 + 4.5 wt% NaPA 8000 + 2.5 wt% Na2SO4 was chosen and applied on the fast centrifugal partition chromatography (FCPC). After optimization, the best operational conditions were identified, i.e. a flow rate of 2.5 mL.min−1 and rotation speed of 2000 rpm at ascending mode, and the best results obtained, meaning a purification of 89.93% and a recovery yield of 82.3%, confirming the potential of FCPC to the continuous purification of EGFP.publishe

Aqueous Biphasic Systems Composed of Cholinium Chloride and Polymers as Effective Platforms for the Purification of Recombinant Green Fluorescent Protein

Green fluorescent protein (GFP) has excellent properties as a biosensor and biomarker; however, its widespread use is limited by its purification costs. Alternative low-cost purification techniques can overcome this issue. The aim of this work was to evaluate aqueous biphasic systems (ABS) composed of cholinium chloride ([Ch]­Cl) and different polymers as effective platforms to recover GFP from cell lysate of recombinant Escherichia coli BL21. All systems completely extracted GFP from cell lysate (>99%) into the polymeric- or [Ch]­Cl-rich phases. In general, [Ch]­Cl-based ABS allowed a good purification capacity (GFP 80–100% pure), with the best results (approximately 100% pure GFP) achieved with a polypropylene glycol (PPG)-400/[Ch]Cl ABS in a single-step extraction or in a two-step extraction (back-extraction) by the integration of a polyethylene glycol (PEG)/sodium polyacrylate+[Ch]­Cl ABS with a following stage using a PEG/[Ch]­Cl-based ABS. Additionally, to demonstrate the potential of the PPG-400/[Ch]Cl ABS in downstream processing, solvent recycling and GFP polishing were carried out using ultrafiltration. Finally, the capacity of the PPG-400/[Ch]Cl ABS to extract other fluorescent proteins was also confirmed. The results clearly demonstrated that the PPG-400/[Ch]Cl ABS can be applied in downstream processing for the purification of proteins, not only enhancing purification yields but also providing simpler, quicker, cost-effective, and biocompatible processes

BIOMOLECULES EXTRACTED BY ATPS: PRACTICAL EXAMPLES

The actual biotechnology industry demands fast and economic upstream and downstream processes to purify biomolecules. In this context, different purification techniques, that offer both high recovery and purity to the final product, have been assayed by different research groups. Liquid-liquid extraction with aqueous two-phase systems is one of the most studied methodologies for bio-separation. This technique presents several advantages such as mild conditions of working, cost-effectiveness, short-time consumption and high recovery percentage of the final product. With the aim to present a comparison of liquid-liquid extractions with other techniques, several aqueous two-phase extraction processes of biomolecules are presented in this review. We presented the advantages and disadvantages of them as of the compared systems. In general, the highest final product purities are achieved when different methodologies are combine, being the chromatographic ones the most applied in the last stages for the high purification factor obtained after them. Alternative methodologies, such as aqueous two-phase systems (ATPS), i.e., PEG/salts or ionic liquids; aqueous two-phase micellar systems, using solvents and surfactants; and extractive fermentation with ATPS, are relevant for both cost-effectiveness and time-saving of the purification process.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq