title: Efficient mannitol production by wild-type Lactobacillus reuteri CRL 1101 is attained at constant pH using a simplified culture medium.
abstract: Mannitol is a natural polyol with multiple industrial applications. In this work, mannitol production by Lactobacillus reuteri CRL 1101 was studied at free- and controlled-pH (6.0-4.8) fermentations using a simplified culture medium containing yeast and beef extracts and sugarcane molasses. The activity of mannitol 2-dehydrogenase (MDH), the enzyme responsible for mannitol synthesis, was determined. The effect of the initial biomass concentration was further studied. Mannitol production (41.5 ± 1.1 g/l), volumetric productivity (Q Mtl 1.73 ± 0.05 g/l h), and yield (Y Mtl 105 ± 11 %) were maximum at pH 5.0 after 24 h while the highest MDH activity (1.66 ± 0.09 U/mg protein) was obtained at pH 6.0. No correlation between mannitol production and MDH activity was observed when varying the culture pH. The increase (up to 2000-fold) in the initial biomass concentration did not improve mannitol formation after 24 h although a 2-fold higher amount was produced at 8 h using 1 or 2 g cell dry weight/l comparing to the control (0.001 g cell dry weight/l). Finally, mannitol isolation under optimum fermentation conditions was achieved. The mannitol production obtained in this study is the highest reported so far by a wild-type L. reuteri strain and, more interestingly, using a simplified culture medium.
authors.affiliation: Departamento de Tecnología y Desarrollo, Centro de Referencia para Lactobacilos (CERELA)-CONICET, Chacabuco 145, 4000, San Miguel de Tucumán, Argentina.
authors.forename: Maria Eugenia
authors.initials: ME
authors.lastname: Ortiz
authors.affiliation: Departamento de Tecnología y Desarrollo, Centro de Referencia para Lactobacilos (CERELA)-CONICET, Chacabuco 145, 4000, San Miguel de Tucumán, Argentina.
authors.forename: Raúl R
authors.initials: RR
authors.lastname: Raya
authors.affiliation: Departamento de Tecnología y Desarrollo, Centro de Referencia para Lactobacilos (CERELA)-CONICET, Chacabuco 145, 4000, San Miguel de Tucumán, Argentina. fmozzi@cerela.org.ar.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Mozzi
mesh_terms: D003470:Culture Media / Q000737:chemistry*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D052200:Limosilactobacillus reuteri / Q000378:metabolism*; D008353:Mannitol / Q000378:metabolism*; D008354:Mannitol Dehydrogenases / Q000032:analysis; D013997:Time Factors
chemical_list: D003470:Culture Media; D008353:Mannitol; D008354:Mannitol Dehydrogenases
keywords: Fermentation; Lactic acid bacteria; Polyol; Sugar alcohol; Sugarcane molasses