Poly(3-Hydroxybutyrate-Co-3-Hydroxyhexanoate): Real-Time Monitoring of Microbial Degradation via Quartz Crystal Microbalance and Electrochemical Measurement

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), produced by some bacteria, including Aeromonas strains, exhibits excellent environmental biodegradability, even in marine environments where biodegradation is typically poor. However, the exact mechanisms underlying this biodegradability remain to be elucidated. To evaluate the mechanisms of microbial degradation of PHBH, focusing on the initial stages, PHBH degradation by Comamonas testosteroni is analyzed, using a quartz crystal microbalance (QCM), cyclic voltammetry (CV), impedance, and scanning electrochemical microscopy (SECM). Real-time monitoring of bacterial adsorption followed by PHBH degradation is quantitatively achieved at the cellular level using a highly sensitive QCM. CV and impedance measurements suggest that microbial degradation of PHBH proceeds in a heterogeneous manner. The SECM observations reveal the heterogeneous microbial degradation of PHBH, which is highly consistent with the QCM, CV, and impedance measurements. These findings indicate that this analytical system, combined with highly sensitive QCM analysis and electrochemical measurement, is an effective tool for studying the microbial degradation of biodegradable plastics.