3-Hydroxypropionate production from myo-inositol by the gut acetogen Blautia schinkii

Species of the genus Blautia are not only abundant in the human gut but also contribute to human well-being. Our study demonstrates that the gut acetogen Blautia schinkii can grow on myo-inositol. We identified the pathway of myo-inositol degradation through a combination of physiological and biochemical studies, genome-wide expression profiling and homology searches. Initially, myo-inositol is oxidized to 2-keto-myo-inositol. This compound is then metabolized by a series of enzymes – a dehydratase, hydrolase, isomerase and kinase – to form 2-deoxy-5-keto-d-gluconic acid 6-phosphate. This intermediate is split by an aldolase into malonate semialdehyde and dihydroxyacetone phosphate, which is an intermediate of the Embden–Meyerhof–Parnas pathway. This pathway leads to the production of pyruvate and, subsequently, acetate. Concurrently, malonate semialdehyde is reduced to 3-hydroxypropionate (3-HP). The genes responsible for myo-inositol degradation are clustered on the genome, except for the gene encoding the aldolase. We identified the putative aldolase Fba_3 and 3-HP dehydrogenase Adh1 encoding genes bioinformatically and verified them biochemically using enzyme assays with heterologously produced and purified protein. The major fermentation end products were 3-HP and acetate, produced in similar amounts. The production of the unusual fermentation end product 3-HP is significant not only for human health but also for the potential bioindustrial production of this highly desired compound.