17A-6 |
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S. PHETSOMPHOU1, C. W. Seo1, A. Shahbazi2, and S. A. Ibrahim1. (1) Food Science & Nutrition Program, North Carolina A&T State Univ., Dept. of Human Environment & Family Sciences, 171-B Carver Hall, Greensboro, NC 27411-1064, (2) Bioenivromental Engineering Program, North Carolina A&T State Univ., Dept. of Natural Resources & Environmental Design, Carver Hall, Greensboro, NC 27411-1064 Lactic acid is a product that has numerous applications in the chemical, pharmaceutical, and food industries. Lactic acid bacteria have been used widely for the production of lactic acid. However, certain nutrients are needed for the maximum production of lactic acid. The objective of this research was to investigate the effect of nutrient supplements and carbohydrate substrates on lactic acid production using free and calcium alginate immobilized Lactobacillus. reuteri L. reuteri MM 2-3 in a free cell form and calcium alginate beads (immobilized) was used to determine lactic acid production in laboratory medium supplemented with either nutrients: yeast extract, beef extract, tryptone peptone, and proteose peptone at 0, 10 and 20% concentrations or carbohydrate substrates: maltose, lactose, glucose, sorbitol and sucrose at 10% concentration. Fermentation experiments were conducted in 500 ml flasks with 300 ml final volume at 37 °C for 24 hrs. At different time intervals (2 hrs), samples were withdrawn, and analyzed for pH values and lactic acid concentrations. Fermentations of immobilized L. reuteri in samples containing yeast extract, phytone and proteose peptone at 20% produced the highest concentrations of lactic acid after 24 hrs with pH measurements (3.20, 3.41, and 3.61, respectively) as compared to the control (4.70). Lactic acid concentration ranged between 9.00 and 12.50. Regarding carbohydrate substrate (sugar) fermentation, maltose produced the lowest pH (3.32) followed by glucose, lactose and sorbitol (3.47, 4.00, and 6.11 respectively). Immobilized cells produced higher lactic acid and in a shorter time when compared to free cells. The results show that immobilized L. reuteri could be used for the production of high lactic acid concentrations in a laboratory media supplemented with both yeast extract and maltose.
Session 17A, Dairy Foods: Cheese and microbiology
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