Metabolic engineering of Cupriavidus necator for L-arginine production

谷氨酸棒杆菌和大肠杆菌的工程菌株是发酵氨基酸生产的主力，这是一个价值数十亿美元的增长行业。然而，这些发酵依赖于第一代生物质原料中的碳，这些原料的成本和供应都在波动。棕榈油的生产每年产生超过3000万吨富碳废物。再加上目前的施肥方法，棕榈油温室气体的排放量至少占到三分之一；相当于6000万吨二氧化碳。这些污染废物有可能被用作氨基酸发酵的新原料；特别是富含氮的精氨酸，它正被用作树木肥料。这样做将通过将碳回收到种植园中来对废物进行定价，同时减少对无机肥料的需求。然而，目前还没有用于这一过程的工业菌株。为此，我们的目标是设计一个微生物细胞工厂，将二氧化碳转化为L精氨酸。铜绿假单胞菌可以自然生长在二氧化碳和氢气上，这使它成为实现这一目的的理想主机底盘。利用代谢工程和合成生物学策略，将开发和优化L精氨酸过量生产菌。这将得到一系列补充的基因组分析的支持，以提供对生物合成途径如何调控的新见解。一旦达到经济上可行的产量和生产力，该菌株将在以二氧化碳为原料的中试规模气体发酵中进行示范。

Engineered strains of Corynebacterium glutamicum and Escherichia coli are the workhorses of fermentative amino acid production, a growing industry worth billions. Yet these fermentations rely upon carbon from first-generation biomass feedstocks, which fluctuate in cost and supply.The production of palm oil generates over 30 million tons of carbon-rich waste each year. Together with current methods of fertilisation, these are responsible for at least a third of palm oil greenhouse gas emissions; the equivalent of 60 million tonnes of carbon dioxide.This polluting waste has the potential to be used as a novel feedstock for amino acid fermentation; specifically nitrogen-rich arginine, which is growing in use as a tree fertiliser. Doing so would valorise the waste by recycling its carbon back into plantations, whilst reducing the need for inorganic fertilisers. However, no industrial strain exists for this process.To this end, we aim to engineer a microbial cell factory for the conversion of carbon dioxide to L-arginine. Cupriavidus necator can naturally grow on carbon dioxide and hydrogen, making it an ideal host chassis for this purpose. Using metabolic engineering and synthetic biology strategies, an L-arginine overproducer will be developed and optimised. This will be supported by a complementary range of -omic analyses to provide novel insight into how the biosynthetic pathway is regulated. Once economically viable yields and productivities have been reached, this strain will then be demonstrated at pilot-scale gas fermentation using carbon dioxide as the feedstock.