Add time:08/01/2019         Source:sciencedirect.com

Microbial hyaluronic acid (bio-HA) is a highly valued product due to its wide range of aesthetic and medical applications. High purity is an essential requirement for those applications. HA is a polyelectrolyte susceptible to structural changes with pH; therefore, precipitation with organic solvents is attractive as a downstream processing step. However, its high hydration capacity requires a low dielectric constant solvent such as isopropyl alcohol (IPA) for better performance. Although precipitation is a typical step of polymer purification, there is still a lack of data relating the changes in the colloidal domain to precipitation performance. Therefore, this work examined the changes in zeta potential (ZP) surface tension (ST) and hydrodynamic size (HS) as functions of pH before and after bio-HA precipitations with IPA from a culture medium containing soy peptone (SP) as the main contaminant. The results showed that the structural and surface changes mediated by pH as well as the proportion of IPA:broth were correlated with the recovery and purity of bio-HA. The best results for recovery (R) and purity (P) were obtained at 2:1 IPA/broth v/v with 76.0 ± 6.6% (R) and 79.0 ± 1.8% (P) at pH 3, as well as 72.0 ± 7.5% (R) and 74.0 ± 2.7% (P) at pH 7. These findings are relevant for a better understanding of the interactions at the colloidal level that lead to the optimization of the bio-HA precipitation step based on the structural and surface properties.

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