Post-consumer plastic poses serious threats to the environment and human health; hence, recycling and disposal are imperative to subdue its impact. For this, developments of advanced technological solutions that are not only sustainable but also environmentally friendly need to be explored in detail. In this investigation, genetically modified leaf-branched compost cutinase (LCC) and TfC from Thermobifida species are processed with subcrystalline polyethylene terephthalate (10 mg/mL) in a batch reactor (BR), a continuous reactor (CSTR), and a cascade of reactors (multiple CSTRs) to examine the degradation of PET at various degrees of micromixing (η→0 to η→∞) and macromixing (tanks 1 to 3) at different surfactant (cetyltrimethylammonium bromide-CTAB) concentrations (1–60 μM). Batch operations are found to be strongly inhibited (competitive) because of the accumulation of BHET (bis(2-hydroxyethyl) terephthalate) equivalent products, hence downgrading BHET formation at all surfactant concentrations as compared to CSTR operation, and 36.27 μg/mL (max.) BHET was observed using LCC, the most efficient enzyme studied in this investigation. The degree of polymerization (DP) of PET was also adjudged during the progress of the enzymatic reaction using the modeling and simulation approach. A maximum BHET formation (51.27 μg/mL) was observed at very low micromixing (η→∞) in CSTR. Under the influence of low micromixing (η→∞), both LCC and TfC show tremendous improvement in BHET formation (>35% for PET–LCC and PET–TfC systems). Further, using a tank-in-series model, upto 263 μg/mL BHET was achieved by connecting 3 tanks in series (higher macromixing limitations) for the PET–LCC system. Hence, an increase in micromixing as well as macromixing limitations helps in achieving greater BHET formation and PET degradation, thereby advancing sustainable plastic degradation by reducing the energy requirement of the process.
Ashwin Gaikwad (Wed,) studied this question.