Simultaneous fermentation and crystallization in succinic acid production

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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 maximu...