Metabolic engineering of edible microorganism for the biomass production from $CO_2$ and formic acid

Abstract

Edible microorganisms are attracting much attention as sustainable food resources to change existing food production system such as agriculture and livestock, which are causing environmental problems including climate change. Therefore, we aimed to establish edible microorganism-based food production system that can utilizes C1 compounds and produce beneficial nutrients including protein as a solution for problems above. Firstly, probiotic strain E. coli Nissle 1917, which has been consumed as a medicine for diarrhea treatment and considered as safe, was chosen as an edible biomass production platform for sustainable food application. In addition, among the C1 compounds, powerful greenhouse gas $CO_2$ and its reduced form formic acid (FA) were selected as alternative carbon sources. To convert the carbon metabolism of E. coli Nissle 1917 to assimilate C1 compounds, we applied systems metabolic engineering strategies. Here, we metabolically engineered E. coli Nissle 1917 strain to produce edible biomass carbon from $CO_2$ and formic acid by reconstruction of Calvin-Bassham-Benson cycle and by tetrahydrofolate cycle together with reverse glycine cleavage pathway. This is the first case of conversion of heterotrophic edible microorganism into synthetic carbon assimilating strain, which is widely applicable for establishment of sustainable edible microorganism production.