Membrane transporters in the bioproduction of organic acids: state of the art and future perspectives for industrial applications

Organic acids such as monocarboxylic acids, dicarboxylic acids or even more complex molecules such as sugar acids, have displayed great applicability in the industry as these compounds are used as platform chemicals for polymer, food, agricultural and pharmaceutical sectors. Chemical synthesis of these compounds from petroleum derivatives is currently their major source of production. However, increasing environmental concerns have prompted the production of organic acids by microorganisms. The current trend is the exploitation of industrial biowastes to sustain microbial cell growth and valorize biomass conversion into organic acids. One of the major bottlenecks for the efficient and cost-effective bioproduction is the export of organic acids through the microbial plasma membrane. Membrane transporter proteins are crucial elements for the optimization of substrate import and final product export. Several transporters have been expressed in organic acid-producing species, resulting in increased final product titers in the extracellular medium and higher productivity levels. In this review, the state of the art of plasma membrane transport of organic acids is presented, along with the implications for industrial biotechnology.This work was supported by the strategic programme UID/BIA/04050/2019 funded by Portuguese fundsthrough the FCT I.P., and the projects: PTDC/BIAMIC/5184/2014, funded by national funds through the Fundacao para a Ciencia e Tecnologia (FCT) I.P. and by the European Regional Development Fund (ERDF) through the COMPETE 2020-Programa Operacional Competitividade e Internacionalizacao (POCI), and EcoAgriFood: Innovative green products and processes to promote AgriFood BioEconomy (operacao NORTE-01-0145-FEDER-000009), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). DR acknowledges FCT for the SFRH/BD/96166/2013 PhD grant. MSS acknowledges the Norte2020 for the UMINHO/BD/25/2016 PhD grant with the reference NORTE-08-5369-FSE-000060. TR acknowledges Yeastdoc European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 764927