Sugaring-out extraction combining crystallization for recovery of succinic acid

In this study, sugaring-out extraction combining crystallization was developed for succinic acid separation and purification. From the different sugaring-out extraction systems investigated, the following order in the phase forming ability of the solvents and sugars were observed: t-butanol > n-propanol > isopropanol, and galactose > glucose > fructose > mannose ≈ sucrose > xylose, respectively. Tert-butanol/glucose system showed the potential superiority in the partition behavior of succinic acid, glucose and solvent. The system parameters influencing the extraction efficiency, such as tie line length, system pH, temperature, glucose, t-butanol and succinic acid concentration were evaluated. The results showed that partition coefficient of succinic acid increased linearly as tie line length increased, and strongly depend on the system pH. 88.15% of succinic acid and 96.72% of t-butanol was distributed into the top phase while 94.69% of glucose into the bottom phase at a system consisting of 27% (w/w) glucose and 40% (w/w) t-butanol under pH 3.0 and temperature 25 °C. Succinic acid concentration had influence on its partition behavior due to its broadened scope of phase formation. The effect of temperature in the t-butanol/glucose system was not obvious for partition of succinic acid. Salts-assisted sugaring-out extraction of succinic acid in t-butanol-glucose system was also investigated. When the mass fraction of (NH4)2SO4 was increased from 1% to 9% (w/w), the recovery of SA from the broth increased from 87.62% to 89.55%. It was noteworthy that t-butanol recovery increased obviously from 96.21% to 99.48%, which means almost all of t-butanol was recovered to the top phase. Finally, succinic acid purification was developed by gradient crystallization after recovering t-butanol by vacuum distillation and glucose by water-washing. By combining sugaring-out extraction with gradient crystallization, an identical total yield (73%) and a higher purity (98%) of succinic acid were obtained. The results obtained in this work support the establishment of sugaring-out extraction combining crystallization as a potential effective and economic strategy for bio-succinic acid separation.