Date of Award
Doctor of Philosophy
Food Science and Human Nutrition
Zivko L. Nikolov
Weak- (Reillex 425 and Riedel-de-Haen VI-15), moderate- (Dowex MWA-1, Dowex WGR-2, Dowex XUS-40283, and Dowex XUS-43432), and strong- (Dowex XUS 40196 and Amberlite IRA-958) base resins were evaluated for their sorption capacities of lactic acid from solutions with different pHs. Composite isotherms and fixed-bed sorption indicated that the sorption capacities of weak- and moderate-base resins decreased markedly as the pH of the feed exceeded the pK a of lactic acid. The decrease in capacity was mainly due to the decrease in concentration of undissociated lactic acid as the pH of the feed increases. The strong-base sorbents exhibited significantly higher sorption capacities for free lactic acid than for lactate. The higher capacities at low pHs were due to the swelling of the resin, thus exposing more sorption sites and creating more space for sorption. The capacity of strong-base resin in fixed-bed sorption remained constant from pH 2 to 6;Riedel-de-Haen VI-15, Dowex MWA-1 and Amberlite IRA-35 were employed in a lactic acid recovery scheme using model fermentation broth. The starting broth (pH 4.5) contained 1% yeast extract, 10% ammonium lactate and 1% glucose. The broth was acidified by using cation exchange resin (Duolite C-464) in H+ form, producing 0.4 bed volume (BV) of acidified broth. The acidified broth (pH 2.9) containing 6% lactic acid and 0.7% glucose was passed through the column until the basic sorbent was saturated. The sorbed lactic acid in the column was eluted using methanol or 5% NH4OH. Lactic acid was completely recovered from VI-15 column after 7 BV of methanol while only 64% was recovered from MWA-1 after 4.5 BV. The 5% NH4OH eluted all lactic acid from MWA-1 column in 1.5 BV with a maximum effluent concentration of 115 mg/mL. High-purity, heat-stable lactic acid was recovered from Riedel-de-Haen VI-15 when the broth was treated with activated carbon and styrene divinylbenzene resin before the acidification step using a strong cation exchanger in H+ form. The lactic acid obtained from real fermentation broth was also high in purity but not heat-stable.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Roque Lagman Evangelista
Evangelista, Roque Lagman, "Recovery and purification of lactic acid from fermentation broth by adsorption " (1994). Retrospective Theses and Dissertations. 11252.