Rapid quantification of polyhydroxyalkanoates accumulated in living cells based on green fluorescence protein labeled phasin: The qPHA method

Polyhydroxyalkanoates (PHA), are microbial polyesters with possibility to replace non-biodegradable petro-plastics. No rapid in situ PHA quantitation method has been available for the past 40 years to replace the traditional method which is complicated, time and labor consuming. Quantification of PHA in living cells were finally developed from fluorescence intensities generated from green fluorescence protein (GFP) fused with the Halomonas bluephagenesis phasin proteins attached on the PHA granules. Phasins PhaP1 and PhaP2 were used to fuse with GFP which reflects PHA accumulation with an R-square over 0.9, respectively. Also, a standard correlation was established to calculate PHA contents based on the fluorescence and cell density recorded via a microplate reader with R-square over 0.95 when grown on various substrates, respectively. The PhaP2-GFP containing H. bluephagenesis was applied successfully to quantify PHA synthesis in a 7.5 L fermenter with high precision. The method is named qPHA.