Design of a minimized and low-cost culture medium for high mannitol production by Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034

Abstract

Mannitol is a natural polyol used in the food, medical and pharmaceutical industries. In this work, a simplified low-cost culture medium using fructose syrup as a carbon source was formulated for mannitol production by Fructobacillus sp. CRL 2054 and F. tropaeoli CRL 2034. To this end, the effect of different medium components in bacterial growth and mannitol synthesis was assessed by applying the Plackett-Burman statistical design. The formulated FSYP-min was used for fermentations at constant pH of 5.0 in a 2 L bioreactor, where two concentrations of fructose syrup (10 and 20 %, w/v, of total sugars) were evaluated. High mannitol concentrations (ca. 90 g/L) and volumetric productivities (3.7 g/L∗h) were achieved by both strains using 20 % (w/v) of sugars; these mannitol values are one of the highest reported for LAB to date. Finally, high-purity mannitol crystals were successfully extracted after fermentation with the formulated culture medium.