Improved recovery and biological activities of an engineered polyene NPP analogue in Pseudonocardia autotrophica

NPP A1 produced by Pseudonocardia autotrophica is a unique disaccharide-containing polyene macrolide. NPP A1 was reported to have higher water solubility and lower hemolytic toxicity than nystatin A1 while retaining its antifungal activity. An engineered NPP A1 analogue, NPP A2, was generated by inactivation of the nppL gene, encoding a P450 monooxygenase in P. autotrophica. The resulting compound exhibited the corresponding chemical structure of NPP A1 but lacked a C10 hydroxyl group. In this study, newly developed crystallization recovery methods for NPP A2 purification, followed by an evaluation of in vitro antifungal activity and hemolytic activity, were performed. The crystallization methods were designed to eliminate the undesired viscous impurities encountered during the NPP A2 purification process, resulting in improved purity from 5.3 to 83.5% w/w. NPP A2 isolated from the improved purification process also exhibited two times higher antifungal activity and 1.8 times higher hemolytic toxicity than those of NPP A1. These results suggest that the minor structural modification of disaccharide-containing polyene macrolides, such as removing a C10 hydroxyl group, might require an alternative recovery process, such as crystallization, to confirm its improved biological activity.