Succinic acid downstream processing

The downstream purification of succinic acid is also key for the fermentation process, which has a cost of about 60-70% of that of the total bioproduction process (Baniel and Eyal 1995). The separation and purification of succinic acid from the fermentation broth has been reviewed in the literature (Zeikus et al. 1999). 

For purification of succinic acid from acidic fermentation broth (pH 3) as obtained by yeast-based fermentation processes, relatively short routes for downstream processing are possible. The protonated form of succinic acid shows much lower solubility in aqueous systems compared to its anionic form. After separation of the cells, the broth is evaporated leading to crystallization of succinic acid, which is then solubilized, purified by ion exchange and crystallized again (Figure 16.4). Since the... 

FIGURE 16 A Display of involved downstream processing steps for purification of succinic acid produced under low and neutral pH scenario. 

Bio-based succinic acid is a very promising compound which can be used in many different application fields and has the potential to substitute several petroleum-based bulk chemicals. Research within the past years led to the development of a number of different production strains, fermentation strategies, and downstream processes suitable for industrial needs. Based on these results, several companies started bio-succinic acid production at industrial scale. The short overview of these companies given above, which is certainly not complete, and... 

Cheng KK, Zhao XB, Zeng J, Wu RC, Xu YZ, Liu DH, Zhang JA. (2012). Downstream processing of biotechnological produced succinic acid. Appl Microbiol Biotechnol, 95, 841-850. 

In 2009, BASF and Purac formed a partnership for the development of the industrial fermentation and downstream processing of biosuccinic acid, and are now establishing a joint venture for the production and sale of biobased succinic acid. The company has been named Succinity GmbH and started up officially in August 2013. The two companies have modified an existing fermentation facility of Purac in Montmelo, Spain, for the production of succinic acid. The annual capacity of the plant is 10,000 metric tonnes and production started in March 2014 [109]. 

There is at this writing no commercial-scale process for the production of succinic acid. There has been activity over the last several years, which is primarily found in the patent literature, to improve the fermentation as well as the downstream process. A great deal of effort was initially spent on Amerobiospirillum succiniciproducens, as this was the first organism observed which could produce succinic acid in levels high enough to envision a commercial process. 

There are a number of patents on the microorganisms, fermentation process, and downstream separation of succinic acid. In addition, there are patents that cover the further conversion of succinate to other products and many patents on the competitive chemical processes that make large-volume chemicals such as 1,4-butanediol. A useful summary of the downstream chemical conversion patents appears in Varadarajan and Miller (1999). While patents have been referenced throughout this section on succinic acid, it is of interest to summarize succinic acid fermentation, strain development, and downstream separation patents here. 

The other key issue for production of large-volume chemicals is the technology needed to further convert succinic acid to other products such as 1,4-butanediol. This process technology must be very competitive with other processes that start with low-cost petrochemical feedstocks. One potential avenue to reducing costs may be the use of crude fermentation broth that is chemically converted and then purified in some further downstream process. 

At the downstream side, the method of THF extraction is unlikely to be applicable on a large scale due to the low solubility of FDCA in this solvent. Well-established methods for the purification of, e.g., bio-based citric, glutamic, and succinic acid may serve as a starting point for optimization, although the specific physical properties of FDCA will eventually require a tailor-made purification process. 

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