Lenuta Kloetzer

Succinic acid fermentation in a stationary-basket bioreactor with a packed bed of immobilized Actinobacillus succinogenes: 1. Influence of internal diffusion on substrate mass transfer and consumption rate

This paper is dedicated to the study on external and internal mass transfers of glucose for succinic fermentation under substrate and product inhibitions using a bioreactor with a stationary basket bed of immobilized Actinobacillus succinogenes cells. By means of the substrate mass balance for a single particle of biocatalysts, considering the Jerusalimsky kinetic model including both inhibitory effects, specific mathematical expressions have been developed for describing the profiles of the substrate concentrations and mass flows in the outer and inner regions of biocatalyst particles, as well as for estimating the influence of internal diffusion on glucose consumption rate. The results indicated that very low values of internal mass flow could be reached in the particles center. The corresponding region was considered biologically inactive, with its extent varying from 0.24% to 44% from the overall volume of each biocatalyst. By immobilization of bacterial cells and use of a basket bed, the rate of glucose consumption is reduced up to 200 times compared with the succinic fermentation system containing free cells.

INFLUENCE OF SOLVENT POLARITY ON INTERFACIAL MECHANISM AND EFFICIENCY OF SUCCINIC ACID REACTIVE EXTRACTION WITH TRI-n-OCTYLAMINE

This article presents the results of a comparative study of reactive extraction of succinic acid with tri-n-octylamine (TOA) dissolved in solvents with different dielectric constants (dichloromethane, n-butyl acetate, and n-heptane), with and without octan-1-ol addition as phase modifier. The positive effect of octan-1-ol on extraction efficiency was quantified by means of amplification factors. For all studied systems, the addition of octan-1-ol into the solvent phase led to an increase of extraction efficiency, the most important effect being recorded for the solvent with the lowest polarity, namely n-heptane. The maximum value of amplification factor was reached for pH = 6 and indicated an increase of reactive extraction yield of about 1.26 times for dichloromethane, 1.55 times for n-butyl acetate, and 2.88 times for n-heptane.

Selective Separation of Carboxylic Acids Obtained by Succinic Acid Fermentation Using Facilitated Pertraction

Formic, acetic, and succinic acids have been selectively separated from their mixture obtained by A. succinogenes fermentation using facilitated pertraction with tri-n-octylamine (TOA). This technique allows recovering formic and acetic acids from the mixture, the feed phase raffinate containing only succinic acid. The pH-gradient between the feed and stripping phases, carrier concentration in liquid membrane, and mixing intensity of the two aqueous phases control the selectivity of acids pertraction, TOA concentration exhibiting the most important influence. At pH-value of feed phase 2, pH-value of stripping phase 10, rotation speed 500 rpm, the maximum selectivity factor (S = 133) was reached for the carrier concentration 70 g L−1.

Synergic Extraction and Transport of Folic Acid through Liquid Membranes

The influence of carrier concentration on the synergic effect induced in the facilitated pertraction of folic acid with the mixture of Amberlite LA-2 and D2EHPA has been analyzed for two liquid membranes with different polarities. The results indicated that the most important synergism can be obtained in the pertraction systems containing low concentrations of D2EHPA and high Amberlite LA-2 concentrations dissolved in a low-polar solvent, namely n-heptane. On the other hand, the stronger synergism corresponding to the acid extraction from the feed phase could lead to a weak synergic effect or negative synergism related to the reextraction into the stripping phase.