The effects of nutrient supplements on the production of lactic acid from cheese whey

Abstract

Purpose: To investigate the effects of microorganism strain, substrate concentration and yeast extract (w/v), MnSO 4 .H 2 O, MgSO 4 .7H 2 O addition to cheese whey solution on the lactic acid production and enantiomeric excess of produced lactic acid. Material and Methods: Fermentations were performed as batch fermentations with 100 mL liquid medium in 250 mL erlenmeyer flasks. The different species of lactic acid bacteria (seven bacteria species), concentrations of yeast extract (0-1% w/v), manganese sulfate (0.003-0.02 % w/v) and magnesium sulfate (0.005-0.01% w/v) were investigated on the lactic acid produc- tion. The medium was inoculated with about 0.04 mg/mL inoculum of bacteria. Lactic acid and lactose was determined by HPLC, with a Phen. Rezex. RHM Mon. (300x7.8 mm) column. Lactic acid enantiomers were determined also by HPLC, using a chiral column (Shodex Orpak CRX-853). Results: Lactic acid concentration was increased about three times according to the control experiment by adding additional nutrient supplements (yeast extract, MnSO 4 ) into the che- ese whey. After 48 hour of fermentation, the highest lactic acid concentration was achieved with Lactobacillus casei NRRL-B-1922 with the presence of 0.4% yeast extract and 0.007% MnSO4. The highest lactic acid concentration and conversion were 61 g/L and 94%, respecti- vely. When only 0.5% yeast extract (w/v) was added to the fermentation medium, approxima- tely the same conversion (93%) was obtained at 48 h of fermentation. Lactic acid produced by L. casei NRRL-B-1922 was mostly L(+) lactic acid and 99% ee was obtained at all conditions. Conclusion: It is provided that only addition of yeast extract into cheese whey should be increase the lactic acid conversion and productivity.