Effects of Different Neutralizing Agents on D-(-)-Lactic Acid Fermentation by <i>Escherichia coli </i>W

Abstract

Effects of NH4OH, KOH, Ca (OH) 2, CaCO3, and a mixture of CaCO3 and NH4OH as neutralizing agents for efficient recovery of lactic acid fermented by Escherichia coli W were investigated. Maximum productivities of lactic acid were 11.3 g/L, 10.7 g/L, 5.5 g/L, 11.9 g/L, and 12.8 g/L respectively. The mixed neutralizing agent of CaCO3 and NH4OH was testified to be better than any single neutralizer used in this study. CaCO3 was the most appropriate neutralizer among the first four neutralizers, which could make lactic acid precipitate in the form of calcium lactate, and facilitate the downstream separation and extraction of lactic acid. Furthermore, it was a slow type of mild neutralizer and had a limited capacity to regulate pH. NH4OH could regulate pH easily, and it was beneficial to cell growth as an additional nitrogen source, thus resulting in a relatively lower lactic acid production.

Microbial production of lactic acid: the latest development

“…In addition, separation of dissolved ammonium lactate from the fermentation broth is cumbersome. Similar to ammonia, sodium has the same inhibitory effect on LA production when used as the neutralizing agent (Tian et al, 2014;Wang et al, 2014;Zhao et al, 2012). Recently, we found that the LA production might be relevant to the ionic strength (I) of the fermentation broth.…”

“…In general, NH 3 , NH 4 OH, KOH, NaOH, NaHCO 3, Ca(OH) 2 and CaCO 3 are routinely used as neutralizing agents (Yen et al, 2010;Zhao et al, 2012). Among them, Ca(OH) 2 and CaCO 3 have the advantage that they precipitate LA as calcium lactate reducing the toxic effects of LA on the growth and morphology of microbial cells (Yen et al, 2010).…”

A roundabout strategy for high-purity glycolic acid biopreparation via a resting cell bio-oxidation catalysis of ethylene glycol

“…The supernatant was left for 24–48 h at 4 °C to induce CG recrystallization. 30 The recrystallized CG was finally air-dried by 4 rounds of recrystallization operation. The purity of CG was determined by HPLC, with the standard errors within 1.0% for the duplicate samples.…”

“…To purify fermentation products, recrystallization is a conventional industrial purification technique that effectively purifies the product from the aqueous phase system. 30,31 We have devised a smart technical route that effectively avoids the high-water solubility barrier in the direct access to GA by a recrystallization technology purifying the intermediate products of GA. Based on the comparative study on the water solubility and crystallization of various glycolates, we found the distinctive characteristics of calcium glycolate (CG) crystallization. Therefore, a novel roundabout strategy was proposed for the high-purity GA bio-preparation from EG.…”