Production of mannitol under different culture conditions and mannitol dehydrogenase activity in Lactobacillus coryniformis subsp.coryniformis CRL1001

M. J. FORNAGUERA, C. RODRÍGUEZ, G. VRANCKEN, T. RIMAUX, G. FONT DE VALDEZ, R. RAYA, L. DE VUYST AND F. MOZZI

San Miguel de Tucumán, Tucumán, Argentina

Simposio; III International Symposium on Lactic Acid Bacteria II Argentinean LAB Net Meeting; 2009

<!-- /* Font Definitions */ @font-face {font-family:Calibri; mso-font-alt:"Century Gothic"; mso-font-charset:0; mso-generic-font-family:swiss; mso-font-pitch:variable; mso-font-signature:-1610611985 1073750139 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin-top:0cm; margin-right:0cm; margin-bottom:10.0pt; margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-AR; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> C 09         PRODUCTION OF MANNITOL UNDER DIFFERENT CULTURE CONDITIONS AND MANNITOL DEHYDROGENASE ACTIVITY IN Lactobacillus coryniformis subsp.coryniformis CRL1001 M. J. Fornaguera1, C. Rodríguez1, G. Vrancken2, T. Rimaux2, G. Font de Valdez1, R. Raya, L. De Vuyst2 and F. Mozzi1. 1Centro de Referencia para Lactobacilos (CERELA-CONICET), Chacabuco 145, 4000- Tucumán, Argentina. 2Research Group of Industrial Microbiology and Food Biotechnology (IMDO), Faculty of Sciences and Bio-engineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium. E-mail: fmozzi@cerela.org.ar Mannitol is a sugar alcohol that is produced by certain bacteria, fungi, yeasts, and plants. This polyol has several applications in the food, pharmaceutical, chemical, and medical industries; however, the main application of this low-calorie sugar is as a food additive because of its sweetening power and it is also applicable in diabetic food products. At present, it is industrially produced by catalytic hydrogenation of fructose/glucose mixtures yielding mannitol in addition to sorbitol. In recent years, the production of mannitol by fermentation has gained much attention, especially involving food-grade microorganisms such as lactic acid bacteria. The purpose of this work was to evaluate mannitol production by the strain Lactobacillus coryniformis subsp. coryniformis CRL1001 under different culture conditions (pH-free and pH-controlled batch fermentations) and to correlate mannitol dehydrogenase activity (MDH) with optimum mannitol production. Bacterial cells were grown in modified MRS medium, containing 7.5% (w/v) of sugar cane molasses, at free or constant pH (6.0, 5.0, and 4.0) and 37°C for 24 h. Cell viability, sugar consumption, and organic acid and mannitol production were determined throughout the fermentations. Maximum mannitol production (40.5 g/l; Yp/s of 91.6%) was found with pH-free fermentations after 24 h, while mannitol production was not improved at the constant pH values assayed (33.1 and 28.9 g/l at pH 6.0 and 5.0, respectively). No cell growth was observed at pH 4.0 Therefore, MDH activity was measured during pH-free fermentations at different time points up to 48 h into fermentation; a positive correlation between MDH activity and mannitol production was observed, the highest specific activity (1.19 U/mg protein) being obtained after 48 h. The mannitol production values obtained here evidence that strain L. coryniformis subsp. coryniformis CRL1001 is an excellent candidate, as a starter or adjunct culture, for the microbial synthesis of mannitol to be produced as additive or for in situ production in mannitol-enriched foods.