Investigation of the metabolic pathways from Xanthomonas axonopodis pv. citri for the utilization of aromatic compounds derived from lignin

Abstract

Lignin is an aromatic heteropolymer of vegetal origin, which corresponds to about 30% of the organic carbon available in our biosphere. In plants, it confers mechanical resistance to cells, support for the vascular system and resistance against pathogens. In industry, it is one of the main byproducts of the papermaking and cellulosic ethanol process, being produced in the scale of thousands of tons per year. Although being a promising source of renewable aromatic compounds for the chemical industry, the current fate of lignin has been burning for energy production. This is due, in part, to the absence of consolidated processes for their conversion into products with higher added value. One of the main bottlenecks for the valorization of lignin lies in its structural heterogeneity. The deconstruction of this polymer generally results in a heterogeneous mixture of aromatic compounds, which imposes considerable technical challenges to reach high purity products. In this context, microorganisms capable of converting this heterogeneous mixture into central compounds of carbon metabolism have been extensively studied to develop a biotechnological solution to this issue. A few bacterial species, such as Pseudomonas putida, have been extensively studied, genetically modified and patented for this purpose. However, other apparently promising species, such as those of the genus Xanthomonas, remain virtually unexplored. Thus, the aim of this project is to evaluate the ability of the bacterium Xanthomonas axonopodis pv citri to use aromatic compounds derived from lignin as a carbon source and to evaluate which metabolic pathways are activated by these compounds to identify the key enzymes of this process. This project is part of a line of research to be inaugurated at CTBE, which aims to contribute to the development of national biotechnological tools for the valorization of lignin. (AU)