Batch Process Lactic Acid Fermentation from Molasses
Author : Catabay, Ferdinand Maggay
Major Adviser : Chay, Pham Binh
Committee Members :
Year : 1991
Month : July
Type : Thesis
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Lactic acid production through batch process fermentation from molasses by free Lactobacillus delbrueckii OBI cells was investigated.
The effects of initial molasses concentration and temperature on the batch production of lactic acid were determined. After five days of fermentation, the maximum lactic acid concentration (42.73 g/l), product yield (0.67) and fermentation efficiency (66.72%) were achieved at 106 g/l initial sugar concentration, temperature at 45°C, 0.118 l/min nitrogen gas flowrate at a constant stirring rate. However, the conversion ratio obtained at 35°C is just 8.83% less than that at 45°C. This indicates that at 35°C, less energy (heat) in needed with just a minimal difference in conversion ratio. Hence, optimum temperature condition lies from 35°C to 45°C.
A steady decrease in pH and sugar concentration was observed in all runs made. However, the run with the lowest final pH and sugar concentration yielded the highest production. This indicated the enhancement of sugar conversion which led to the accumulation of lactic acid. Increasing rate of lactic acid accumulation was observed as the initial sugar concentration was increased. Furthermore, depleting conversion ratio was achieved at decreasing sugar concentration during the course of fermentation. Also, the maximum production was achieved at set temperature for optimum cell growth of L. delbrueckii species. However, increasing the temperature beyond the optimum cell growth exhibited an intolerable decrease in product formation.
A comparison of the results of this work with those reported in the literature shows a slight difference attributed mainly to the type of microorganisms used and the characteristics of the substrate utilized.
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