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

Batch fermentations were performed to investigate the effect of manganese a ddition, in the form of MnSO4.H2O, on the performance of Lactobacillus case i for producing L-lactic acid from whey permeate supplemented with yeast ex tract. There was a particular emphasis on evaluating how little yeast extra ct and MnSO4 . H2O is required while still obtaining high sugar conversion and lactic acid yield, as nutrient supplementation is a raw material cost a nd can lead to extra residual impurities remaining after fermentation. The addition of MnSO4 . H2O had a significant beneficial affect with the fermen tation time being reduced from 120 to 24 h for permeate supplemented with 0 .50%w/v yeast extract. Fermentations were performed with MnSO4 . H2O concen trations in the range of 0.001-0.03 g/l. From 0.005 to 0.03 g/l, the fermen tation performance was very similar, however at the low concentration of 0. 001 g/l, the fermentation was significantly slower. With MnSO4 . H2O additi on. the yeast extract concentration was reduced to 0.30%w/v while still mai ntaining high sugar conversion and lactic acid yield, however the fermentat ion was slower at 37 h. At 0.1%w/v yeast extract supplementation. the ferme ntation performance was poor with only 67% sugar conversion after 150 h of fermentation. (C) 2001 Elsevier Science Ltd. All rights reserved.