Rhodopseudomonas palustris CGA009 polyhydroxybutyrate production from a lignin aromatic and quantification via flow cytometry

Polyhydroxyalkanoates are biopolymers with the potential to replace petroleum-based plastics but are limited by higher productioncosts. For the first time, (i) polyhydroxybutyrate (PHB) was produced by the metabolically versatile Rhodopseudomonas palustris CGA009 from the lignin breakdown product p-coumarate as a renewable carbon source, and (ii) quantification of PHB via flow cytometry was conducted with this highly pigmented bacterium. PHB titer ranged from 0.08 to 0.41 g/L and yielded a 68.4% carbon conversion efficiency. An optimized protocol using either Nile Red or BODIPY 493/503 lipophilic stains yielded high linear fitness for fluorescence intensity with both PHB titer (R² = 0.9384 and R² = 0.9747 respectively) and cell count (R² = 0.9383 and R² = 0.9955 respectively). This quick and precise method for high-throughput quantification of both PHB and cell count coupled with the highest PHB titer from a lignin breakdown product to date from R. palustris make this study novel.