Production of natural fiber reinforced thermoplastic composites through the use of polyhydroxybutyrate-rich biomass

Previous research has demonstrated that production of natural fiber reinforced thermoplastic composites (NFRTCs) utilizing bacterially-derived pure polyhydroxybutyrate (PHB) does not yield a product that is cost competitive with synthetic plastic-based NFRTCs. Moreover, the commercial production of pure PHB is not without environmental impacts. To address these issues, we integrated unpurified PHB in NFRTC construction, thereby eliminating a significant energy and cost sink (ca. 30-40%) while concurrently yielding a fully biologically based commodity. PHB-rich biomass synthesized with the microorganism Azotobacter vinelandii UWD was utilized to manufacture NFRTCs with wood flour. Resulting composites exhibited statistically similar bending strength properties despite relatively different PHB contents. Moreover, the presence of microbial cell debris allowed for NFRTC processing at significantly reduced polymer content, relative to pure PHB-based NFRTCs. Results further indicate that current commercial PHB production yields are sufficiently high to produce composites comparable to those manufactured with purified PHB.