Optimization of critical factors to enhance polyhydroxyalkanoates (PHA) synthesis by mixed culture using Taguchi design of experimental methodology

► Taguchi DOE methodology was applied to optimize mixed culture PHA production. ► Microenvironment (80%) and pH (11%) showed significant contribution in PHA production. ► Glucose, phosphorous, nitrogen and VFA had significant interactive effects. ► Optimization improved PHA production by over 31%. ► PHA production through wastewater treatment significantly reduces the production cost. Optimizing different factors is crucial for enhancement of mixed culture bioplastics (polyhydroxyalkanoates (PHA)) production. Design of experimental (DOE) methodology using Taguchi orthogonal array (OA) was applied to evaluate the influence and specific function of eight important factors (iron, glucose concentration, VFA concentration, VFA composition, nitrogen concentration, phosphorous concentration, pH, and microenvironment) on the bioplastics production. Three levels of factor (21×37) variation were considered with symbolic arrays of experimental matrix [L18–18 experimental trails]. All the factors were assigned with three levels except iron concentration (21). Among all the factors, microenvironment influenced bioplastics production substantially (contributing 81%), followed by pH (11%) and glucose concentration (2.5%). Validation experiments were performed with the obtained optimum conditions which resulted in improved PHA production. Good substrate degradation (as COD) of 68% was registered during PHA production. Dehydrogenase and phosphatase enzymatic activities were monitored during process operation.