Abstract
A strain of Lactobacillus brevis was isolated from a spoiled pickle sample and propagated in MRS liquid medium. The strain possessed high mannitol dehydrogenase activity. The free and immobilized cells in calcium alginate gel beads were used for the production of mannitol using batch culture in bioconversion medium (BCM). The highest mannitol yield was achieved after four days of incubation at 37 oC using cells concentration of 2x106 cells/ml. The reuse of the cells for mannitol production led to a little decrease in their produtibility. The effect was minor with immobilized cells. Mannitol production was proportional to fructose concentration in BCM medium while there was no effect upon using potassium phosphate buffer medium. The continuous mannitol production by immobilized cells was conducted in a glass column. A reverse relationship was noticed between fructose solution flow rate and mannitol yield, but the production rate was higher at higher flow rates. Thus, it is advised to apply fast flow rate with repeated substrate recycling in order to achieve the desired conversion of fructose.
