21EBTA: NO CARBON LOST - ELIMINATING CO2 PRODUCTION FROM FERMENTATION PROCESSES

The world currently faces a number of crises, but none more potentially devastating than climate change. Perversely, it has been during the period of the global pandemic that any remaining doubts that man is not responsible have seemingly evaporated. During this period, the occurrence of extreme weather patterns appear to have proliferated with headline news reporting on floods, heatwaves, forest fires, hurricanes/tornados and the continuing documentation of melting ice sheets. All is a consequence of use of fossils fuels for our energy and chemicals manufacture and the consequent emissions of the Greenhouse gas (GHG), carbon dioxide (CO2).

Whilst it is conceivable that the ingenuity of humankind can expand our array of alternative energy sources (wind, solar, hydro, battery power) to a level that dispense with the need for using fossil fuels for energy and heating, modern society is entirely reliant on the chemicals and materials that are currently derived from oil. Almost everything that surrounds us that is not made of metal, wood, stone, glass, wool or cotton is made from oil. That includes plastics, carpets, clothing, shoes, cosmetics, medicines, wind turbine blades, boats, etc. Accordingly, one of the greatest challenges facing society is the future sustainable production of chemicals from non-petrochemical resources while at the same time reducing greenhouse gas (GHG) emissions.

The solution is to derive processes that can convert plant material, or biomass, into the chemicals and materials we need. This may be accomplished by microbial fermentation processes wherein the biomass is broken down either through the action of hydrolytic enzymes into simple sugars or through the action of heat into simple single carbon gases CO and CO2 and hydrogen. The latter process is called gasification, and the gas mixture generated referred to as synthesis gas or syngas. These simple forms of carbon, sugar or syngas, may then be fermented by microbes into a desired product. A simple example would be making beer, where the yeast microbe converts sugar into ethanol.

The exploitation of biomass in this way will feature prominently in meeting the UKs NetZero targets. Theoretically, any microbe can be engineered to make any chemical. However, traditional, carbohydrate-based fermentation processes, such as ethanol production, waste more than one third of the carbon which is not incorporated into the product but lost in the form of CO2. Eliminating this loss would ablate the emission of a greenhouse gas that is inherent to microbial fermentations and dramatically improve productivity, potentially by greater than 50%. This project, NO CARBON LOST, explicitly sets out to develop microbes and processes that grow on the deconstructed biomass with releasing CO2 and makes more product.

The foundations of our strategy were initiated during lockdown and draw on current activity at SBRC Nottingham related to exploitation of gaseous and sugar feedstocks. We will use monocultures to exploit a platform bacterial strain to make an alcohol from biomass-derived sugars or syngas while at the same time while simultaneously fixing CO2. In parallel, we will use an artificial synthetic, community comprising an engineered biomass-degrading bacterium and a Co2-consumimg microbe, to make the desired products (an alcohol and a volatile fatty acid) without CO2 production. We will also produce a biodegradable plastic using a combination of the two. The project will be underpinned by computerised modelling of the processes in operation. The work undertaken will be carefully monitored and ensured to undertaken in a socially acceptable manner.

NO CARBON LOST seeks to build on the knowledge and capabilities of SBRC Nottingham in engineering the biology of gas fermenting chassis to introduce a step-change in fermentation processes traditionally used with carbohydrate feedstocks, further reducing the carbon footprint of biomass exploitation.

Sugar-based fermentation processes waste more than one third of the carbon which is not incorporated into the product but lost as CO2. We will eliminate carbon loss during biomass-based biological conversions using mono- or mixed culture systems to make products that include alcohols and a bioplastic, without releasing CO2. Our strategy will help the UK meet NetZero targets and benefit the bioeconomy by improving the productivity of renewable processes based on biomass. Our objectives will be progress through 6 workpackages:-

[WP1] we will use monocultures to exploit a platform strain of Cupriavidus necator to make ethanol from biomass-derived hydrolysates that has been engineered to co-utilise sugar (glucose and xylose) while simultaneously fixing CO2.

[WP2] we will use a synthetic, anaerobic community comprising an engineered cellulolytic Clostridium sp. and an acetogen, to make the desired products (propanol or proprionate) without CO2 production.

[WP3] we will engineer C. necator to utilise CO, ensuring that all of the carbon in biomass-derived syngas is used.

[WP4], the modifications made in WP3 will be incorporated with relevant modifications to the WP1 platform strain to explore the use of mixotrophy in the generation of the biopolymer poly-(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV.

[WP5] The project will be underpinned by genome scale modelling of the mono- and mixed cultures

[WP6] Provide RRI training and support for all researchers on the project