(18d) Increased Production of Yersiniabactin (Ybt) and the Anthranilate Analog through Media Optimization and Ybt Metal Binding Characterization

Yersiniabactin (Ybt) is a mixed nonribosomal peptide-polyketide natural product that binds a wide range of metals with the potential to impact processes requiring metal retrieval and removal. The heterologous production of Ybt and an associated anthranilate analog are increased through systematic screening and optimization of culture medium components. Specifically, a Plackett-Burman design-of-experiments methodology was used to screen 22 components and to determine those contributing most to siderophore production. L-cysteine, L-serine, glucose, and casamino acids significantly contributed to the production of both compounds. Ybt and the anthranilate analog titers were increased to 867 ± 121 mg/L and 16.6 ± 0.3 mg/L, respectively, an increase of ~3,800% and ~7,900% relative to production in M9 medium.

The range of metals that Ybt forms a complex with were determined by using mass spectrometry. Using LC-MS the analysis of water samples exposed to aqueous and surface-localized Ybt, quantitative assessment of binding was completed with metals that included palladium, magnesium, and zinc. In total, Ybt showed affinity for 10 metals. Next, Ybt-modified XAD-16N resin (Ybt-XAD) was utilized to quantify the degree of metal binding and metal removal abilities, showing a rank order of Fe>Ga>Ni>Cu>Cr≈Zn>Co>Pd>Mg>Al. Batch tests were conducted using Ybt-XAD for the treatment of wastewater from a local precious metal plating company, showing selective removal of nickel from the aqueous effluent.