A robotic platform to screen aqueous two-phase systems for overcoming inhibition in enzymatic reactions

Practical deployment of automation to expedite aqueous two-phase extraction

The feasibility of bioprocess development relies heavily on the successful application of primary recovery and purification techniques. Aqueous two-phase extraction (ATPE) disrupts the definition of "unit operation" by serving as an integrative and intensive technique that combines different objectives such as the removal of biomass and integrated recovery and purification of the product of interest. The relative simplicity of processing large samples renders this technique an attractive alternative for industrial bioprocessing applications. However, process development is hindered by the lack of easily predictable partition behaviours, the elucidation of which necessitates a large number of experiments to be conducted. Liquid handling devices can assist to address this problem; however, they are configured to operate using low viscosity fluids such as water and water-based solutions as opposed to highly viscous polymeric solutions, which are typically required in ATPE. In this work, an automated high throughput ATPE process development framework is presented by constructing phase diagrams and identifying the binodal curves for PEG6000, PEG3000, and PEG2000. Models were built to determine viscosity- and volume-independent transfer parameters. The framework provided an appropriate strategy to develop a very precise and accurate operation by exploiting the relationship between different liquid transfer parameters and process error. Process accuracy, measured by mean absolute error, and device precision, evaluated by the coefficient of variation, were both shown to be affected by the mechanical properties, particularly viscosity, of the fluids employed. For PEG6000, the mean absolute error improved by six-fold (from 4.82% to 0.75%) and the coefficient of variation improved by three-fold (from 0.027 to 0.008) upon optimisation of the liquid transfer parameters accounting for the viscosity effect on the PEG-salt buffer utilising ATPE operations. As demonstrated here, automated liquid handling devices can serve to streamline process development for APTE enabling wide adoption of this technique in large scale bioprocess applications.

Microfluidic aqueous two-phase system-based nitrifying bacteria encapsulated colloidosomes for green and sustainable ammonium-nitrogen wastewater treatment

A novel strategy was proposed for preparing micro-scale monodisperses nitrifying bacteria (NB) encapsulated Ca-Alg@CaCO₃ colloidosomes by exploiting capillary microfluidic device, as an attempt to treat ammonium-nitrogen wastewater in an environment-friendly, efficient and repeatable manner based on the aqueous two-phase (ATPS) system. By complying with the spatial confined urease mediate biomineralization reactions, ATPS droplets (Dextran in Polyethylene glycol) containing urease, NB regent and alginate were used as templates to prepare 500 μm Ca-Alg@CaCO₃ colloidosomes with 16.48 Mpa mechanical strength. The activity of NB encapsulated in the colloidosomes was high. The simulated wastewater treated with the colloidosomes achieved a high removal rate even at harsh temperature and pH value. In both simulated and real wastewater treatment, prolonged reuse times (216 h) with high removal rate (＞90%, after being applied 72 h) were obtained by using Ca-Alg@CaCO₃ colloidosomes, as compared with that (96 h) by using general alginate microbeads.

A integrated process for nitrilase-catalyzed asymmetric hydrolysis and easy biocatalyst recycling by introducing biocompatible biphasic system

The whole-cell nitrilase-catalyzed asymmetric hydrolysis of nitriles is a green and efficient preparation approach for chiral carboxylic acids, but often suffers from toxicity and cell lysis from organic substrates. In this work, a novel integrated process for whole-cell nitrilase-catalyzed asymmetric hydrolysis was developed for the first time by introducing a biocompatible ionic liquid (IL)-based biphasic system. The whole-cell nitrilases displayed an outstanding stability and recyclability in the biphasic system and still retained > 85% activity even after 7 cycles reaction. A preparative-scale fed-batch hydrolysis of o-chloromandelonitrile to (R)-o-chloromandelic acid (R-CMA) was performed using the integrated process. The results revealed a yield of 91.3% and a space-time yield of 746.4 g·L^-1·d^-1, which are currently the highest reported values for R-CMA biosynthesis. The proposed integrated process avoids substrate inhibition, facilitates the reusability of whole-cell nitrilases, and thus shows great potential for the sustainable production of chiral carboxylic acids.

Enzymatic Hydrolysis of Sugarcane Bagasse in Aqueous Two-Phase Systems (ATPS): Exploration and Conceptual Process Design

The enzymatic conversion of lignocellulosic material to sugars can provide a carbon source for the production of energy (fuels) and a wide range of renewable products. However, the efficiency of this conversion is impaired due to product (sugar) inhibition. Even though several studies investigate how to overcome this challenge, concepts on the process to conduct the hydrolysis are still scarce in literature. Aqueous two-phase systems (ATPS) can be applied to design an extractive reaction due to their capacity to partition solutes to different phases in such a system. This work presents strategies on how to conduct extractive enzymatic hydrolysis in ATPS and how to explore the experimental results in order to design a feasible process. While only a limited number of ATPS was explored, the methods and strategies described could easily be applied to any further ATPS to be explored. We studied two promising ATPS as a subset of a previously high throughput screened large set of ATPS, providing two configurations of processes having the reaction in either the top phase or in the bottom phase. Enzymatic hydrolysis in these ATPS was performed to evaluate the partitioning of the substrate and the influence of solute partitioning on conversion. Because ATPS are able to partition inhibitors (sugar) between the phases, the conversion rate can be maintained. However, phase forming components should be selected to preserve the enzymatic activity. The experimental results presented here contribute to a feasible ATPS-based conceptual process design for the enzymatic conversion of lignocellulosic material.

Spirulina platensis based biorefinery for the production of value-added products for food and pharmaceutical applications

In this present study, microalgal phycobiliproteins were isolated and purified via potential biphasic processing technique for pharmaceutical as well as food applications. The algal pre-treatment techniques were studied to enhance the yield of microalgal phycobiliproteins from the biomass. The proposed methods were optimised to obtain the best recovery yield of phycobiliproteins that can be isolated from the biomass. The phycobiliproteins were further purified using liquid biphasic system. The results showed that microalgal phycobiliproteins of high purity and yield was achieved using sonication treatment (20% power, 50% duty cycle and 7 min of irradiation time) with the biphasic system, where the purification fold of 6.17 and recovery yield of 94.89% was achieved. This work will provide insights towards the effective downstream processing of biomolecules from microalgae.