Widespread distribution of genes in Proteobacteria reveals key enzymes for 5-hydroxymethylfurfural conversion.

Furans represent a class of promising chemicals, since they constitute valuable intermediates in conversion of biomass into sustainable products intended to replace petroleum-derivatives. Conversely, generation of furfural and 5-hydroxymethylfurfural (HMF) as by-products in lignocellulosic hydrolysates is undesirable due its inhibitory effect over fermentative microorganisms. Therefore, the search for furans-metabolizing bacteria has gained increasing attention since they are valuable tools to solve these challenging issues. A few bacterial species have been described at genetic level, leading to a proposed HMF pathway encoded by a set of genes termed /, although some enzymatic functions are still elusive. In this work we performed a genomic analysis of major subunits of furoyl-CoA dehydrogenase orthologues, revealing that the furoic acid catabolic route, key intermediate in HMF biodegradation, is widespread in proteobacterial species. Additionally, presence/absence profiles of / genes in selected proteobacterial strains suggest parallel and/or complementary roles of enzymes with previously unclear function that could be key in HMF conversion. The furans utilization pattern of selected strains harboring different / gene sets provided additional support for bioinformatic predictions of the relevance of some enzymes. On the other hand, at least three different types of transporter systems are clustered with / genes, whose presence is mutually exclusive, suggesting a core and parallel role in furans transport in Proteobacteria. This study expands the number of bacteria that could be recruited in biotechnological processes for furans biodetoxification and predicts a core set of genes required to establish a functional HMF pathway in heterologous hosts for metabolic engineering endeavors.