In silico Prediction of Metabolic Targets for 3-Hydroxypropanoate Production in E. coli

3-hydroxypropionate (3-HPP) has great potential to serve as a building block for the chemical industry as its bifunctional character and high reactivity make it suitable for replacing petroleum-derived chemicals. Since the chemical processes proposed for 3-HPP synthesis are highly toxic and environmentally harmful, this compound is not produced on an industrial scale nowadays. Therefore, fermentative bioprocesses are promising alternatives for producing 3-HPP. Hence, this work aimed to identify non-intuitive reactions that can be engineered for optimizing 3-HPP production in E. coli by the β-alanine pathway. First, the corresponding reactions for 3-HPP biosynthesis were introduced into a genomic-scale metabolic model of E. coli K-12 MG1655 (iML1515). Subsequently, using the software Optflux, in silico 3-HPP production was optimized with an evolutionary algorithm that searched for suitable flux values for the reactions in the model, by under/overexpressing them to enhance 3-HPP formation using xylose or glucose as carbon sources. Results showed that alanine racemase overexpression and, L-valine transaminase and L-alanine transaminase underexpression were the main targets. These modifications were found to increase L-glutamate while decreasing L-alanine pools, thus favoring L-aspartate aminotransferase and β-alanine: pyruvate transaminase reactions towards 3-HPP production. These results will be further assessed in vivo in a 3-HPP production strain.