Biocatalytic Synthesis Using Self-Assembled Polymeric Nano- and Microreactors.

Biocatalysis is increasingly being explored for the sustainable development of green industry. Though enzymes show great industrial potential with their high efficiency, specificity, and selectivity, they suffer from poor usability and stability under abiological conditions. To solve these problems, researchers have fabricated nano- and micro-sized biocatalytic reactors based on the self-assembly of various polymers, leading to highly stable, functional, and reusable biocatalytic systems. This Review highlights recent progress in self-assembled polymeric nano- and microreactors for biocatalytic synthesis, including polymersomes, reverse micelles, polymer emulsions, Pickering emulsions, and static emulsions. We categorize these reactors into monophasic and biphasic systems and discuss their structural characteristics and latest successes with representative examples. We also consider the challenges and potential solutions associated with the future development of this field.

Responsive Emulsions for Sequential Multienzyme Cascades.

Multienzyme cascade biocatalysis is an efficient synthetic process, avoiding the isolation/purification of intermediates and shifting the reaction equilibrium to the product side.. However, multienzyme systems are often limited by their incompatibility and cross-reactivity. Herein, we report a multi-responsive emulsion to proceed multienzyme reactions sequentially for high reactivity. The emulsion is achieved using a CO2 , pH, and thermo-responsive block copolymer as a stabilizer, allowing the on-demand control of emulsion morphology and phase composition. Applying this system to a three-step cascade reaction enables the individual optimal condition for each enzyme, and a high overall conversion (ca. 97 % of the calculated limit) is thereby obtained. Moreover, the multi-responsiveness of the emulsion allows the facile and separate yielding/recycling of products, polymers and active enzymes. Besides, the system could be scaled up with a good yield.

Living whole-cell catalysis in compartmentalized emulsion.

Whole-cell biocatalysis plays an important role in biotransformation with unique features such as good tolerance of solvents and easy recycling. However, the relatively low catalytic efficiency limits their use in real production. In this study, a multi-compartmentalized emulsion in organic solvent was constructed to encapsulate living cells for enhanced catalytic performance. Extraordinary large interfacial area of the emulsion improved the bioactivity of Escherichia coli (E. Coli) cells up to 137 times compared to a standard biphasic system. The emulsion was stabilized by a biocompatible polymer and prepared by gentle shaking by hand, which resulted in good cell viability. Moreover, the encapsulated cells could be easily recycled, and the activity remained more than 70% after five cycles. This work provides a promising approach for utilizing whole-cell catalysts for efficient organic catalysis.

Compartmentalized Aqueous-Organic Emulsion for Efficient Biocatalysis.

The design and construction of polymeric compartmentalized structures in water have been intensively explored for controllable catalysis, but there is still the challenge of setting up catalytic compartments in organic media. Here, we designed a simple block copolymer, PCL-b-PEG-b-PCL, to construct a stable and multi-compartmentalized emulsion in an organic solvent by hand-shaking. This gentle emulsion preparation allowed a successful encapsulation of vulnerable biocatalysts such as benzaldehyde lyase (BAL) and alcohol dehydrogenase (ADH). The compartmentalization provided the emulsion with an exceptionally large interfacial area that could enhance BAL activity up to 225 times as compared to the traditional biphasic system. Moreover, the system could be easily scaled up due to its facile preparation with low cost. Therefore, our results pave the way for developing compartmentalized structures in solvents for biocatalysis in large-scale synthetic chemistry.