The production of mannitol by Lactobacillus intermedius NRRL B-3693 using inulin as a substrate was investigated at pH 5.0 and 37 degrees C. The bacterium produced mannitol (106.2 +/- 0.3 g l(-1)) from dilute acid hydrolyzate (pH 2.0, 121 degrees C, 15 min) of inulin (150 g l(-1)) in 34 h. It also produced mannitol from inulin by simultaneous saccharification and fermentation (SSF) at pH 5.0 and 37 C using inulinase (8 U g(-1) substrate). From 300 g l(-1) inulin, the L. intermedius B-3693 produced 207.4 +/- 1.2 g mannitol in 72 h by SSF. The fermentation time decreased from 72 to 62 h using a mixture of fructose and inulin (1:1, total, 300 g l(-1)). When fructose and inulin mixture (3:5, total 400 g l(-1)) was used as substrate, the bacterium produced 227.9 +/- 1.8 g mannitol l(-1) from both inulin and fructose with a yield of 0.57 g g(-1) substrate after 110 h of SSF. This is the highest level of mannitol ever produced by a microorganism reported in literature. Published by Elsevier Inc.