Polyphenols are molecules with known antioxidant activity having a multitude of biotechnological applications, like colorants and nutraceuticals. There has been a growing interest in implementing a process using genetically modified organisms for their production, due to the disadvantages associated with the production of these molecules by plant extraction or chemical synthesis. However, by inserting a specific pathway in a microorganism for the production of a given polyphenol, most likely a highly similar, chemically related polyphenol, will be produced as well (e.g., resveratrol and pinosylvin). The main goal of the work described in this paper is to develop a downstream process to purify a complex fermentation broth containing similar, hydrophobic polyphenols to the desired molecule only. The purification of hydrophobic polyphenols from the remaining broth components is most frequently performed by reverse-phase adsorption. However, because of very similar affinity and therefore low selectivity, the peaks of closely related polyphenols tend to superimpose. The strategy proposed in this work is to collect low purity (60%) fractions of both polyphenols and to use subsequent preferential crystallization with two coupled crystallizers to increase their purity to the desired level. To provide a proof of principle, a case study with two polyphenols with similar solubility curves in water-ethanol mixtures was selected: Naringenin and trans-resveratrol. In each crystallization vessel - A and B - a solution 60% pure in the respective polyphenol was the starting point. The appropriate seed crystals were then added, in order to promote crystal growth of the desired molecule in each vessel. During the process, fluid from vessel A could be pumped to vessel B and vice-versa. Appropriate filters were inserted to avoid the transfer of crystals of the undesired polyphenol. The goal was to simultaneously optimize the temperature profile in each vessel and the optimal flow rate profile from vessel A to vessel B and vice-versa. Applying this approach, both polyphenols were recovered in their solid form with an increased purity. In the case of trans-resveratrol its purity increased to 97%, with 66% recovery, showing that preferential crystallization is a viable method to separate and purify highly similar polyphenols in their solid state.

Preferential crystallization for the purification of highly similar polyphenols

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.