A Prospective Life Cycle Assessment (LCA) of Monomer Synthesis: Comparison of Biocatalytic and Oxidative Chemistry.

Biotechnological processes are typically perceived to be greener than chemical processes. A life cycle assessment (LCA) was performed to compare the chemical and biochemical synthesis of lactones obtained by Baeyer-Villiger oxidation. The LCA is prospective (based on experiments at a small scale with primary data) because the process is at an early stage. The results show that the synthesis route has no significant effect on the climate change impact [(1.65±0.59) kg CO 2 gproduct -1 vs. (1.64±0.67) kg CO 2 gproduct -1 ]. Key process performance metrics affecting the environmental impact were evaluated by performing a sensitivity analysis. Recycling of solvents and enzyme were shown to provide an advantage to the enzymatic synthesis. Additionally, the climate change impact was decreased by 71 % if renewable electricity was used. The study shows that comparative LCAs can be used to usefully support decisions at an early stage of process development.

Toward Upscaled Biocatalytic Preparation of Lactone Building Blocks for Polymer Applications.

Although Baeyer-Villiger monooxygenases (BVMOs) have gained attention in recent years, there are few cases of their upscaled application for lactone synthesis. A thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) was applied to the oxidation of 3,3,5-trimethylcyclohexanone using a glucose dehydrogenase (GDH) for cofactor regeneration. The reaction progress was improved by optimizing the biocatalyst loading, with investigation into oxygen limitations. The product concentration and productivity were increased by keeping the substrate concentration below the inhibitory level via continuous substrate feeding (CSF). This substrate feeding strategy was evaluated against two biphasic reactions using either toluene or n-butyl acetate as immiscible organic solvents. A product concentration of 38 g L-1 and a space-time yield of 1.35 g L-1 h-1 were achieved during the gram-scale synthesis of the two regioisomeric lactones by applying the CSF strategy. These improvements contribute to the large-scale application of BVMOs in the synthesis of branched building blocks for polymer applications.

Application of a thermostable Baeyer-Villiger monooxygenase for the synthesis of branched polyester precursors.

BACKGROUND: It is widely accepted that the poor thermostability of Baeyer-Villiger monooxygenases limits their use as biocatalysts for applied biocatalysis in industrial applications. The goal of this study was to investigate the biocatalytic oxidation of 3,3,5-trimethylcyclohexanone using a thermostable cyclohexanone monooxygenase from Thermocrispum municipale (TmCHMO) for the synthesis of branched ϵ-caprolactone derivatives as building blocks for tuned polymeric backbones. In this multi-enzymatic reaction, the thermostable cyclohexanone monooxygenase was fused to a phosphite dehydrogenase (PTDH) in order to ensure co-factor regeneration. RESULTS: Using reaction engineering, the reaction rate and product formation of the regio-isomeric branched lactones were improved and the use of co-solvents and the initial substrate load were investigated. Substrate inhibition and poor product solubility were overcome using continuous substrate feeding regimes, as well as a biphasic reaction system with toluene as water-immiscible organic solvent. A maximum volumetric productivity, or space-time-yield, of 1.20 g L-1 h-1 was achieved with continuous feeding of substrate using methanol as co-solvent, while a maximum product concentration of 11.6 g L-1 was achieved with toluene acting as a second phase and substrate reservoir. CONCLUSION: These improvements in key process metrics therefore demonstrate progress towards the up-scaled Baeyer-Villiger monooxygenase-biocatalyzed synthesis of the target building blocks for polymer application. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Exploring the Substrate Scope of Baeyer-Villiger Monooxygenases with Branched Lactones as Entry towards Polyesters.

Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts that are able to convert cyclic ketones into lactones by the insertion of oxygen. The aim of this study was to explore the substrate scope of several BVMOs with (biobased) cyclic ketones as precursors for the synthesis of branched polyesters. The product structure and the degree of conversion of several biotransformations were determined after conversions by using self-sufficient BVMOs. Full regioselectivity towards the normal lactones of jasmatone and menthone was observed, whereas the oxidation of other substrates such as α,ß-thujone and 3,3,5-trimethylcyclohexanone resulted in mixtures of regioisomers. This exploration of the substrate scope of both established and newly discovered BVMOs towards biobased ketones contributes to the development of branched polyesters from renewable resources.

Promoting Mechanochemistry of Covalent Bonds by Noncovalent Micellar Aggregation.

Optical reporting of covalent bond scission in self-assembled structures in water is an important step toward the detection of forces in biological systems. Here we show that micelles of a diblock copolymer comprising hydrophobic poly(butyl acrylate) and hydrophilic poly(acrylic acid) blocks connected by an off-center mechanoresponsive moiety are mechanochemically active when sonicated in aqueous solution. Facile optical read-out of the force-activation is warranted by formation of a blue-fluorescent anthracene cleavage from the mechanophore, an anthracene-maleimide Diels-Alder adduct. In contrast to the efficient bond scission when the block copolymers are noncovalently anchored in liquid-like micellar cores, isolated unimers in solution are not activated by ultrasonication because the dimensions and viscous drag are drastically lower. These results demonstrate that covalent mechanochemistry can be enabled by noncovalent interactions.