SuCCEED: Sustainable Commodity Chemicals through Enzyme Engineering & Design

Commodity chemicals underpin various aspect of modern everyday life, and are mass produced on a global scale. They underpin the production of plastics/polymers, dyes/pigments, cosmetics/detergents etc, and are normally derived from finite geological sources. In view of the need to move towards a more sustainable and circular economy, viable routes for the bioproduction of commodity chemicals are urgently required. One of the key challenges for such routes is that they must operate at relatively low profit margins and at appropriate bulk scale. This presents a significant hurdle to commercial deployment, but, given the scale of commodity chemical production, viable biomanufacturing routes would offer substantial impact upon the global efforts to reduce CO2 emissions.

In addition to the challenges posed at economic and technical levels, the very nature of most commodity chemicals all too often renders them incompatible with direct production by microorganisms. This is due to the inherent reactivity and associated toxicity of these compounds. Furthermore, the relatively slow accumulation of the product during fermentation all too frequently leads to downstream side reactions. Nevertheless, various routes to a wide range of commodity chemicals of interest have been reported, but suffer from low productivity for these reasons.

By contrast, fermentation can yield high levels of biocompatible precursors such as ethanol/lactic acid etc as frequently used in brewing/diary industry. These compounds in turn can be converted to a limited range of commodity chemicals through downstream processes. By analogy, we propose that both existing and novel bioroutes to commodity chemicals would benefit from a similar two-step approach. In the first step, we seek to achieve accumulation of suitable biocompatible precursors from 2G/3G derived biomass. In the second step, we will use enzymatic conversion to yield the desired commodity chemical product. Crucially, separation of microbial growth from chemical production is afforded by such a two-step process, bypassing the issue of toxicity/side-reactions during fermentation. As a proof-of-principle, we recently applied this strategy to bio-styrene production, achieving a 5-fold increase on styrene production levels compared to previous methods.

In collaboration with Shell, we seek to further enhance the new styrene bioproduction process and demonstrate production at scales appropriate for further industrial development. Furthermore, we seek to demonstrate that similar strategies can be successfully applied to the production of a wider range of commodity chemicals, including aldehydes, dienes, dicarboxylic acids etc. To this end, we have brought together an interdisciplinary team of biochemists, protein engineers, synthetic biologists, chemists and chemical engineers to provide proof-of-principle for scalable production of multiple commodity chemicals using post-fermentative enzymatic conversion to support creation of viable biorefineries.

The SuCCEED partnership will seek new biomass-based routes to deliver commodity chemicals at scale, using approaches compatible with the relatively low profit margins associated. It will focus on production of insoluble commodity chemicals where possible, to aid in purification and follow-on conversion. Furthermore, it seeks to address toxicity/side-reaction issues associated with many commodity chemicals head on, by separation of the in vivo microbial conversion of 2G/3G derived biomass from the final enzyme mediated chemical production steps. This will be achieved through the use of robust in vitro biocatalytic process, based on lyophilised whole-cell biocatalysts converting a biocompatible precursor accumulated at high levels in the fermentation step to the target chemical. Preliminary data for production of styrene, alfa-olefins and FDCA supports the validity of this approach and will serve as initial targets for scale-up and development of suitable routes to relevant biocompatible precursors. Robust microbial chassis and pathways/control elements will be developed as a route to cost reduction associated with sterilisation costs. Ultimately, we seek to provide new to market commodity polymers for net zero that are recyclable with minimal energy input, thus minimising environmental impact. Rational protein engineering will be combined with directed evolution to expand the scope of C-H activating peroxidases to support production of cyclolactones as a suitable monomer precursor. New life cycle assessment models will be developed for bio-based chemicals to evaluate and compare the novel routes developed in the research proposal with traditional routes. We thus seek to provide proof-of-principle for scalable production of multiple commodity chemicals from 2G/3G biomass at TRL4, using in vitro enzymatic conversion combined with robust dark fermentation processes where appropriate to support creation of a viable biorefineries.