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Applied and Environmental Microbiology, June 2003, p. 3069-3076, Vol. 69, No. 6
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.6.3069-3076.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Increased Production of Folate by Metabolic Engineering of Lactococcus lactis

Wilbert Sybesma, Marjo Starrenburg, Michiel Kleerebezem, Igor Mierau, Willem M. de Vos, and Jeroen Hugenholtz*

Wageningen Centre for Food Sciences, NIZO Food Research, 6718 ZB Ede, The Netherlands

Received 25 November 2002/ Accepted 6 March 2003

The dairy starter bacterium Lactococcus lactis is able to synthesize folate and accumulates large amounts of folate, predominantly in the polyglutamyl form. Only small amounts of the produced folate are released in the extracellular medium. Five genes involved in folate biosynthesis were identified in a folate gene cluster in L. lactis MG1363: folA, folB, folKE, folP, and folC. The gene folKE encodes the biprotein 2-amino-4-hydroxy-6-hydroxymethyldihydropteridine pyrophosphokinase and GTP cyclohydrolase I. The overexpression of folKE in L. lactis was found to increase the extracellular folate production almost 10-fold, while the total folate production increased almost 3-fold. The controlled combined overexpression of folKE and folC, encoding polyglutamyl folate synthetase, increased the retention of folate in the cell. The cloning and overexpression of folA, encoding dihydrofolate reductase, decreased the folate production twofold, suggesting a feedback inhibition of reduced folates on folate biosynthesis.

* Corresponding author. Mailing address: Department of Flavor, Nutrition and Natural Ingredients, NIZO Food Research, P.O. Box 20, 6718 ZA Ede, The Netherlands. Phone: 31-(0)318-659629. Fax: 31-(0)318-650400. E-mail: hugenhol{at}nizo.nl.

Applied and Environmental Microbiology, June 2003, p. 3069-3076, Vol. 69, No. 6
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.6.3069-3076.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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