Co-conversion of CO2 and refractory organics into bioplastics through a stable biocarrier

Abstract

An attractive solution to traditional plastics is scaling up the microbial system to produce bioplastics like polyhydroxyalkanoates (PHAs). Herein, we developed a dynamic microbial ecosystem on porous biocarrier for conversion of refractory organics to bioplastics. biocarriers of 25 mm sized were packed in a 5 L bioreactor and operated for 200 days, to achieve stable performance for commercial applications. Reaching to bioreactor stability, microbial ecosystem utilized quinoline (5.2 kg/m³/day) for carbon & nitrogen metabolism, phenol (4.5 kg/m³/day) to trigger synthesis of PHAs, pyridines (4.2 kg/m³/day) to manufacture hydroxy fatty acid polyesters, NH₄⁺(7.2 kg/m³/day) to regulate symbiosis, NO₃/NO₂ (1.2 kg/m³/day) to serve as mediators and electron acceptors. On 200th day, bioplastic production reached to 76.8 (kg/m³/day) with stable pollutants degradation of 70.3 (kg/m³/day). Purity of the bioplastics remained quite high (average 90 %) after 100 days of bioreactor operation. Interestingly, PHAs synthesis was triggered (31–581 g/day) with increased CO₂ fixation from 45 to 594 (mol/h/g protein), due to the growth of CO₂ assimilators. The developed biocarriers could be directly poured into the secondary tank of the existing wastewater treatment plants (WWTPs), which will not only produce bioplastics but also boost treatment efficiency and resource recovery potential of WWTPs.