BACKGROUND: Preferential crystallization is a common technique used in the purification of enantiomers, proving that crystallization may also be applied to the purification of very similar molecules by seeding the solution with the desired compound. Nonetheless, its application to other organic molecules is less widely documented in the literature. Knowing that chemically related polyphenols are generally co-produced by fermentation and their purification can be too expensive for their market value, this technique may contribute to developing a downstream process with less expensive steps. The goal of this work is to show the applicability of the preferential crystallization concept to the purification of similar polyphenols - naringenin and trans-resveratrol - with either single or coupled crystallizers. RESULTS: After developing the required crystallization kinetic models, an experiment using two coupled vessels was devised, where a 63% yield of naringenin and 44% yield of trans-resveratrol was obtained, with ≥98% purity in both cases. When the vessels were working independently, 81% of pure trans-resveratrol (started 60% pure) and 70% of pure naringenin (started 68% pure) were recovered. CONCLUSION: The experiments performed show the possibility of separately purifying two similar molecules (from 60% to roughly 100%) with promising yields, despite their similar solubility. This method, which can be significantly improved, might provide an economically attractive way for the production of low added value products.

BACKGROUND: The growing interest in polyphenols has led to the design of industrial-scale processes able to produce them by fermentation and recover them in a more sustainable way. The goal of this work is to present two integrated approaches for the recovery of resveratrol, obtained through fermentation. The production of resveratrol using Corynebacterium glutamicum and its continuous removal using a hydrophobic resin is described. Batch production is compared with in situ product removal, where Amberlite XAD-7HP is either directly added to the medium (direct adsorption) or is present in an external column (external adsorption). RESULTS: For both adsorption strategies tested, the amount of extracellular resveratrol increased from 75% to at least 90% of the total amount produced. However, lower total resveratrol concentrations were attained – 3.6 and 2.2 mg L^-1, for the external and direct contact strategies, respectively, versus 5.3 mg L^-1 for batch experiments. CONCLUSIONS: The proposed in situ removal strategies demonstrated the potential of increasing the excretion of resveratrol produced intracellularly. These process configurations may not only lead to a simpler downstream process design, but also to the avoidance of potential problems with the toxicity of polyphenols to the cells, especially when larger titers are obtained.