부산대학교 도서관

ABSTRACT: A neutralizing agent is usually employed to counteract the pH reduction during lactic acid fermentation by Rhizopus oryzae. Calcium carbonate (CaCO) is used as such a pH controlling agent. The low solubility of CaCO in the fermentation broth could however lead to low efficiency in pH control and cause problems in the subsequent purification process. Therefore, an alternative agent in place of CaCO was examined in this study. The effect of four different neutralizing agents, including CaCO, sodium hydroxide (NaOH), ammoniacal solution and sodium bicarbonate (NaHCO) on lactic acid production and the morphology of the pellets were investigated. Results indicated that CaCO was still the preferred choice, because of the pellet morphology and the highest lactic acid concentration (43.3 g/L) obtained in the batch using 60 g/L of sweet potato starch as feedstock. It is noteworthy that the lactic acid purification is relatively easier when using NaHCO instead of CaCO, due to the higher solubility of sodium lactate than calcium lactate. Therefore, even the batch with CaCO had a slightly higher productivity (1.23 g/L/h) than the batch with NaHCO (1.14 g/L/h), NaHCO might be the first choice for process designers whenever recovery is vital.