Chemical Recycling of Polyhydroxybutyrate (PHB) into Bio-Based Solvents and Their Use in a Circular PHB Extraction

Two novel protocols for the chemical valorization of polyhydroxybutyrate (PHB) were developed, aiming at production two bio-based molecules: methyl 3-hydroxybutyrate (MHB) and 3-methoxybutyrate (MMB). Optimized reaction conditions applied to pure PHB inclusions inside bacterial cells as starting materials. MHB was synthesized through a single-step catalytic methanolysis, while MMB three-step process: thermolytic distillation give crotonic acid (CA), esterification crotonate (MC), oxa-Michael addition MeOH. The obtained tested solvents recovery itself both from freeze-dried single strain cultures (SSC) mixed microbial (MMC) with low medium contents (22–57 wt %). High achieved: up 96 ± 1% 98 MMB. Extraction MMC slurry (with content 39% on dry weight) also performed, recovering 77 2% using 92 purities excellent molecular weights polydispersity indexes extracted Solubility in water, octanol/water partition coefficients (log Kow), aerobic ready biodegradability evaluated.