co-production of 1,3 propanediol and 3HP from glycerol by clostridium pasteurianum

To compete with existing petrochemical-based chemical manufacturing processes, low cost feedstocks for biological fermentation processes are essential, since the feedstock typically equates to over 60% of the overall production cost. Glycerol is a versatile carbon and energy source and presently it is produced in large scale as the principle by-product (10% w/w) of the biodiesel industry and it is now essentially a waste product. Clostridial species, and in particular Clostridium pasteurianum, can grow particularly well on glycerol as a sole carbon and energy source and transform it into a number of useful chemicals such as 1,3-propanediol (PDO), acetone, butanol, ethanol etc.

Until now, the opportunity to use Clostridium strains for the high level production of chemicals from glycerol has been limited due to the lack of genetic engineering tools. However, the requisite tool box needed for the optimisation of the metabolic pathways required for butanol production by Clostridium pasteurianum has been developed within the Clostridia Research Group of SBRC Nottingham. It is the purpose of this PhD project to use synthetic biology approaches and the University of Nottingham tool box to generate an engineered strain of C. pasteurianum able to over-produce a number of useful chemicals using glycerol as a feedstock. The initial focus will be the important platform chemical 3-hydroxypropanoic acid (3-HP) which can serve as a starting point for production of acrylic acid (representing a $ 10 billion market together with the respective esters), acrylamide, malonic acid, poly(hydroxypropionate), 1,3-propanediol, and propiolactone. The approach taken will be to both introduce genes encoding the requisite enzymes and to knock-out genes specifying competing pathways. This will involve bringing about essential refinements to the tools available, including the generation of restriction minus hosts and the use of CRISPR/Cas9 technology. Thereafter, other products may be targeted.