Effects of pH and corn steep liquor variability on mannitol production by Lactobacillus intermedius NRRL B-3693

Abstract

Lactobacillus intermedius NRRL B-3693 produced mannitol, lactic acid, and acetic acid when grown on fructose at 37 degrees C. The optimal pH for mannitol production from fructose by the heterofermentative lactic acid bacterium (LAB) in pH-controlled fermentation was at pH 5.0. It produced 160.7 +/- 1.1 g mannitol in 40 h with a volumetric productivity of 4.0 g l(-1) h(-1) in a simplified medium containing 250 g fructose, 50 g corn steep liquor (CSL), and 33 mg MnSO(4) per liter. However, the mannitol production by the LAB was severely affected by the variability of CSL. The supplementation of CSL with soy peptone (5 g/l), tryptophan (50 mg/l), tryptophan (50 mg/l) plus tyrosine (50 mg/l), or commercial protease preparation (2 ml/100 g of CSL) enhanced the performance of the inferior CSL and thus helped to overcome the nutrient limitations.