Valorization of Commercial Sugarcane Molasses as a Sustainable Substrate for the Production of Bacterial Polyhydroxybutyrate
摘要
This work presents an easy and less polluting routine for obtaining bacterial polyhydroxybutyrate (PHB-B), using low-cost inputs. The objective of this research is to evaluate the thermal and thermodynamic properties of PHB-B obtained from the bacterium Cupriavidus necator and commercial sugarcane molasses substrate. Commercial PHB Biocycle® (PHB-C) was also evaluated for comparative purposes. The thermal properties of both biopolymers were similar. PHB-B showed a well-defined cold crystallization peak at 93.31 ± 0.68 °C, while PHB-C exhibited a broad peak at 61.28 ± 0.26 °C. The degrees of crystallinity of PHB-B and PHB-C were 48.56 ± 0.49 and 54.72 ± 0.48%, respectively. PHB-B displayed a double melting peak at 158.43 ± 2.4 and 168.73 ± 1.32 °C, whereas PHB-C showed only one at 167.04 ± 0.82 °C. A crystallization temperature in the second heating of 44.65 ± 0.02 °C was observed only for PHB-C. The initial and maximum temperatures of thermal degradation were 192.39 ± 2.19 °C and 254.86 ± 1.37 °C for PHB-B, and 217.76 ± 1.80 °C and 261.89 ± 0.91 °C for PHB-C. In both cases, the degradation process occurred in a single step. The activation energy revealed that PHB-C is more resistant to thermal degradation than PHB-B. The thermodynamic parameters indicate that the thermal degradation profile is endothermic and that the thermal degradation processes are non-spontaneous for both biopolymers. This study demonstrates that a low-cost substrate can produce bacterial PHB with thermal and thermodynamic properties of interest for the processing, enhancing its potential applications.