
Carboxylic acids (CAs) are considered key players in the implementation of more sustainable industrial processes due to their potential to replace a set of oil-derived commodity chemicals and there is growing interest in producing them through microbial processes. While many CAs are intermediates of microbial central carbon metabolism, and therefore envisaging their production in a host of choice is relatively straightforward; for other CAs this approach is difficult. This could be because they do not occur naturally (as is the case for levulinic acid) or because the described production pathway cannot be easily ported (as it is the case for adipic, muconic or glucaric acids). In a review published in Journal of Fungi, Nuno Mira’s team (iBB) reviewed the synthetic biology approaches that have been made towards enabling the production of non-natural CAs in microbes, with a large emphasis on metabolic retrobiosynthesis methodologies. Additionally, the authors also reviewed the pathway prospecting studies towards microbial levulinic, poly-lactic and methacrylic acid production, as two case-studies where there is a need to bridge the gap between natural CAs and their non-natural industrial derivatives.