Production of mannitol from inulin by simultaneous enzymatic saccharification and fermentation with Lactobacillus intermedius NRRL B-3693

The production of mannitol by Lactobacillus intermedius NRRL B-3693 using inulin as a substrate was investigated at pH 5.0 and 37 °C. The bacterium produced mannitol (106.2 ± 0.3 g l−1) from dilute acid hydrolyzate (pH 2.0, 121 °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.