Simultaneous fermentation and crystallization in succinic acid
production

Abstract: Succinc acid is a high potential candidate as a building block chemical, as
an origin for many other chemicals made from renewable resources. It has been
successfully produced by fermentation and can be processed into a great
variety of products. Therefore, it is an object of interest for the growing
biobased industry.

This paper deals with the succinate fermentation of an E. coli strain, called
AFP184 and the influence of the succinate concentration on the productivity
in this fermentation. The fermentations are run in two parts: an aerobic
growth phase where cells are produced, and an anaerobic production phase in
which succinate is produced. It has been investigated if the NH4OH used as a
base chemical in the aerobic phase has any effect on the growth
characteristics and if an inhibiting effect of the growing succinate
concentration could be countered by precipitating the succinate with Ca(OH)2.
It was determined that the growth rate was highest when NH4OH was used as
base and further fermentations used NH4OH during the aerobic phase and NH4OH,
Ca(OH)2 or mixtures thereof during the anaerobic phase. It was found that the
best results were obtained if Ca(OH)2 was added to a fermentation ran with
NH4OH as base. This lead to a high productivity that could be kept up over a
total succinate concentration of 50 g/l, which in previous studies had been
the maximum concentration achieved.

The fermentations were done at the Division of Biochemical and chemical
process engineering at Luleå university of technology.