The viability of forward osmosis in the concentration of biologically produced fumaric acid using l-alanine as a draw solution

Abstract

Separation and concentration processes of fumaric acid from industrial products and down streams have been a subject of wide range in research. With the emergence of Forward Osmosis (FO) technology attention has shifted to utilising it in downstream processing. This study has investigated the viability of FO technology in concentration a fumaric acid solution produced by continuous microbial fermentation process using L-Alanine as a novel draw solution (DS). Thin Film Composite (TFC) aquaporin protein flat sheet membrane was used in the FO set up. L-Alanine was used as a DS at a concentration of 0.085 g/mL. The DS concentration was chosen based on preliminary studies which were conducted to determine the optimal DS concentration which achieved the highest water flux with the lowest reverse solute diffusion. The fumaric acid produced by continuous microbial fermentation process was investigated as a Feed Solution (FS). The biologically produced Fumaric acid was obtained from a continuous microbial fermentation process developed by the Bioreaction Engineering group at University of Pretoria. Rhizopus oryzae fungus was utilised in the fermentation process with glucose as the substrate. The influence of temperature on the efficiency of the FO process was also investigated. The results show that fumaric acid solution concentrated by 26.00 % and 19.80 % in 32 ℃ and 17 ℃, respectively. The results demonstrate FO technology to be an effective way to concentrate the fumaric acid solution produced by continuous microbial fermentation process. However, achieving high concentration has been limited because of high residual concentration of glucose and other minerals in the biological process. This lead to reduce the net driving osmotic force through the membrane. The initial concentration of glucose contributed with 50.50 % of overall osmotic pressure of FS, while the initial concentration of fumaric acid contributed only with 12.20 %. Minimising the residual glucose concentration could lead to a doubling of the fumaric acid concentration in the FO process.