Understanding the biocalorimetric and respirometric behaviour of co-culture (R. eutropha, P. putida and A. vinelandii) in poly (3-hydroxybutyrate) batch production

Abstract

Limiting nitrogen and excess carbon sources induce accumulation of the bioplastic, Poly-(3-hydroxybutyrate) (PHB) as inclusion bodies in microbes. Here, we designed a co-culture (R. eutropha, P.putida, A.vinelandii) that produced higher PHB yield than in monocultures or pairwise combination. PHB concentration of 8.3 ± 0.42 g/L, which is 63% of total Cell Dry Mass (CDM), was achieved using co-culture in batch mode of operation in biocalorimeter. Maximum total biomass based specific growth rate (μX: 0.49 h−1) was achieved in co-culture and bioenergetics profiles were compared for individual and co-culture. In this co-culture, P. putida and R. eutropha greatly contributed to PHB accumulation, while A. vinelandii induced faster growth. Aeration and agitation rates were optimized in the biocalorimeter, 1 liter per minute (lpm) and 150 rotations per minute (rpm) respectively for improved PHB yield. Oxygen uptake rate and carbon dioxide evolution rates correlated well with heat profiles, suggesting aerobic metabolism in consortia. Cellular accumulation of PHB granules in the co-culture was visualized using fluorescent microscopy.