Mannitol production by Lactobacillus reuteri CRL 1101 using a low-cost culture medium

M.E. ORTIZ; G. VIGNOLO; R.R. RAYA; F. MOZZI

Estambul

Congreso; 23rd International ICFMH Symposium Food Micro 2012: Global Issues of Food Microbiology.; 2012

International Committee on Food Microbiology and Hygiene of the IUMS

Mannitol is a natural polyol mainly used in the food industry as low-calorie sweetener (referred as E421 in the European Union) being applicable for diabetic food products. As food ingredient, it is also used in "breath-freshening" products due to its negative enthalpy and capability to mask undesirable tastes of many compounds. In addition, it has been claimed to display health-promoting (antioxidant, anticariogenic) effects. In the last years, efforts have been made to produce mannitol through fermentations using lactic acid bacteria. To produce mannitol in an efficient and cost-effectively way, a few low-cost substrates have been recently investigated. In this work, we aimed to design a minimum culture MRS-based medium using sugarcane molasses as carbon source for the production of mannitol by Lactobacillus reuteri CRL 1101. The effect (by omission or addition) of each MRS component on cell growth (OD and cell count), pH and mannitol production (HPLC) by L. reuteri CRL 1101 were determined in a minimum culture medium at 37°C under free- and controlled-pH fermentations for 24 h. The formulated low-cost culture medium, containing beef extract, yeast extract, and either glucose plus MnSO4 or sugarcane molasses, showed similar microbial growth patterns to that obtained in MRS. L. reuteri CRL 1101 successfully produced good amounts of mannitol using this low-cost minimum culture medium. Optimal cell growth (log CFU/ml: 8.9±0.2) and mannitol production (150.3±11.3 mM, Ymtl: 100 %) were obtained in free-pH cultures after 24 h of fermentation. These values were improved (cell growth, log CFU/ml: 9.2±0.3 and mannitol production, 180.1±15.9 mM) in fermentations under constant-pH of 5.0 although with a lower yield (Ymtl: 89 %). The design of an inexpensive and more competitive culture medium for the biotechnological production of mannitol represents an important approach for the microbial synthesis of mannitol at industrial scale.