Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The extensive application of P3HB encounters a challenge due to its high production costs, prompting the investigation of sustainable alternatives, including the utilization of waste and new production routes involving CO₂ and CH₄. This study provides a valuable comparison of two P3HBs synthesized through distinct routes: one via cyanobacteria (Synechocystis sp. PCC 6714) for photoautotrophic production and the other via methanotrophic bacteria (Methylocystis sp. GB 25) for chemoautotrophic growth. This research evaluates the thermal and mechanical properties, including the aging effect over 21 days, demonstrating that both P3HBs are comparable, exhibiting physical properties similar to standard P3HBs. The results highlight the promising potential of P3HBs obtained through alternative routes as biomaterials, thereby contributing to the transition toward more sustainable alternatives to fossil polymers.

Polypropylene (PP) is a multifunctional and widely applied polymer. Nevertheless, its low energy surface and poor adhesion are well-known and might impair some prospective applications. Aiming to overcome these limitations, PP composites can be applied as a tool to enhance PP surface energy and then increase its practical adhesion. In this work, Kraft lignin (KL) was chemically modified and blended with PP. In short, KL was hydroxypropylated and further reacted with acetic anhydride (A-oxi-KL) or maleic anhydride (M-oxi-KL). Lignin modifications were confirmed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). PP-composites with different lignin contents, as well as pristine PP, were characterized in terms of their thermal behavior, morphology, surface energy, and practical adhesion by DSC, scanning electron microscopy (SEM), contact angle measurement, and peeling tests, respectively. Lignin incorporation did not affect the PP degree of crystallization. The lignin modifications led to a better compatibility with the PP matrix and surface energies up to 86% higher than neat PP. Increases of up to 66% in the peel strength were verified. Composites with M-oxi-KL showed the best adhesion performance, confirming the lignin functionalization is an efficient approach to improve the practical adhesion of PP films.