Effect of manganese on Lactobacillus casei fermentation to produce lactic acid from whey permeate

Batch fermentations were performed to investigate the effect of manganese addition, in the form of MnSO4.H2O, on the performance of Lactobacillus casei for producing L-lactic acid from whey permeate supplemented with yeast extract. There was a particular emphasis on evaluating how little yeast extract and MnSO4 . H2O is required while still obtaining high sugar conversion and lactic acid yield, as nutrient supplementation is a raw material cost and can lead to extra residual impurities remaining after fermentation. The addition of MnSO4 . H2O had a significant beneficial affect with the fermentation time being reduced from 120 to 24 h for permeate supplemented with 0.50%w/v yeast extract. Fermentations were performed with MnSO4 . H2O concentrations in the range of 0.001-0.03 g/l. From 0.005 to 0.03 g/l, the fermentation performance was very similar, however at the low concentration of 0.001 g/l, the fermentation was significantly slower. With MnSO4 . H2O addition. the yeast extract concentration was reduced to 0.30%w/v while still maintaining high sugar conversion and lactic acid yield, however the fermentation was slower at 37 h. At 0.1%w/v yeast extract supplementation. the fermentation performance was poor with only 67% sugar conversion after 150 h of fermentation. (C) 2001 Elsevier Science Ltd. All rights reserved.