Purification of lactic acid obtained from a fermentative process of cassava syrup using ion exchange resins

Abstract

In the present work, the production of lactic acid (LA) via fermentation was evaluated, and its subsequent separation by means of an ion exchange resin system. For the biosynthesis of LA, the Lactobacillus brevis strain was used, which was cultivated under anaerobic conditions using a medium of low nutritional content based on cassava hydrolyzate, called HY1. For a culture kinetics of 120 h, in a 7.5 L bioreactor, the highest concentration of LA found was 24.3 +/- 0.07 g AL / L, with a productivity of 0.20 g / L / h, at pH 6.5 and 38 ° C. For the recovery of LA, the ion exchange resins Amberlite IRA-400 and IR-120 were used. Initially, the adsorption isotherm of AL (25 ° C) on the Amberlite IRA-400 resin activated in its Cl-, OH- and HSO4 2- form was determined. The Cl- form of the activated resin was evaluated at pH 5, while the OH form was evaluated at pH 3.5 and 6.3. The highest adsorbate content was 0.59 +/- 0.03 g AL / g resin at pH 6.3, when the resin was activated in its OH- form. Next, the breakdown curves were developed in the Amberlite IRA-400 resin at pH 3 and 5, and 0.5 and 1mL / min of feed flow. The maximum concentration of adsorbed AL was 0.109 +/- 0.005 g AL / g resin at pH 3 and 0.5 mL / min. Finally, the recovery of AL was evaluated in a system of serial columns packed with Amberlite IRA-400 and IR-120 resins; The recovery of LA was 77% and 73%, when the system was adjusted to 0.5mL / min, 25 ° C, pH 3 and 5, respectively.