title: Folic Acid Production by Engineered Ashbya gossypii.
abstract: Folic acid (vitamin B9) is the common name of a number of chemically related compounds (folates), which play a central role as cofactors in one-carbon transfer reactions. Folates are involved in the biosynthesis and metabolism of nucleotides and amino acids, as well as supplying methyl groups to a broad range of substrates, such as hormones, DNA, proteins, and lipids, as part of the methyl cycle. Humans and animals cannot synthesize folic acid and, therefore, need them in the diet. Folic acid deficiency is an important and underestimated problem of micronutrient malnutrition affecting billions of people worldwide. Therefore, the addition of folic acid as food additive has become mandatory in many countries thus contributing to a growing demand of the vitamin. At present, folic acid is exclusively produced by chemical synthesis despite its associated environmental burdens. In this work, we have metabolically engineered the industrial fungus Ashbya gossypii in order to explore its potential as a natural producer of folic acid. Overexpression of FOL genes greatly enhanced the synthesis of folates and identified GTP cyclohydrolase I as the limiting step. Metabolic flux redirection from competing pathways also stimulated folic acid production. Finally, combinatorial engineering synergistically increased the production of different bioactive forms of the folic vitamin. Overall, strains were constructed which produce 146-fold (6595µg/L) more vitamin than the wild-type and by far represents the highest yield reported.
authors.affiliation: Metabolic Engineering Group, Department of Microbiology and Genetics, University of Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Serrano-Amatriain
authors.affiliation: Metabolic Engineering Group, Department of Microbiology and Genetics, University of Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ledesma-Amaro
authors.affiliation: Department of Food Science and Nutrition, Faculty of Veterinary Sciences, University of Murcia, Campus de Espinardo, 30071 Espinardo (Murcia), Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: López-Nicolás
authors.affiliation: Department of Food Science and Nutrition, Faculty of Veterinary Sciences, University of Murcia, Campus de Espinardo, 30071 Espinardo (Murcia), Spain.
authors.forename: Gaspar
authors.initials: G
authors.lastname: Ros
authors.affiliation: Metabolic Engineering Group, Department of Microbiology and Genetics, University of Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Jiménez
authors.affiliation: Metabolic Engineering Group, Department of Microbiology and Genetics, University of Salamanca, Campus Miguel de Unamuno, E-37007 Salamanca, Spain. Electronic address: revuelta@usal.es.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Revuelta
mesh_terms: D055169:Eremothecium / Q000235:genetics* / Q000378:metabolism*; D005492:Folic Acid / Q000096:biosynthesis* / Q000235:genetics*; D060847:Metabolic Engineering
chemical_list: D005492:Folic Acid
keywords: Ashbya gosypii; Folic acid; Metabolic engineering; Microbial production; Vitamin B9