Process engineering for microbial production of 3-hydroxypropionic acid.

Due to concerns about the unsustainability and predictable shortage of fossil feedstocks, research efforts are currently being made to develop new processes for production of commodities using alternative feedstocks. 3-Hydroxypropionic acid (CAS 503-66-2) was recognised by the US Department of Energy as one of the most promising value-added chemicals that can be obtained from biomass. This article aims at reviewing the various strategies implemented thus far for 3-hydroxypropionic acid bioproduction. Special attention is given here to process engineering issues. The variety of possible metabolic pathways is also described in order to highlight how process design can be guided by their understanding. The most recent advances are described here in order to draw up a panorama of microbial 3-hydroxypropionic acid production: best performances to date, remaining hurdles and foreseeable developments. Important milestones have been achieved, and process metrics are getting closer to commercial relevance. New strategies are continuously being developed that involve new microbial strains, new technologies, or new carbon sources in order to overcome the various hurdles inherent to the different microbial routes.