Sustainable production of the biodegradable polymer polyhydroxybutyrate (PHB) from hardwood extract hydrolysates through green recovery by enzymatic digestion

Plastic products have been playing essential important roles in people's everyday life. The increasing concerns about the environmental problems caused by petrochemical based plastics and forthcoming exhaustion of fossil resources has renewed the search for environmentally friendly and sustainable alternatives. Polyhydroxyalkanoats (PHAs) stand out as a promising replacement to conventional plastic polymers, because they have similar physical properties as petroleum-derived polymers while they possess the important attributes of biodegradability and biocompatibility.;Wood extract hydrolysate (WEH) was used as fermentation feedstock for polyhydroxybutyrate (PHB) production by Burkholderia cepacia. Two detoxification methods were studied. PHB production yield were improved by over 200% by particle removal and 160% by sodium dithionite treatment. A green, effective, and economic method to recover polyhydroxybutyrate (PHB) from Bukerholdria cepacia culture broth by pancreatin was studied and characterized. Through this approach, purity of PHB increased from 43.2% to 90.6%, and recovery of PHB reached 93.5%. Further purification by sodium dodecyl sulfate treatment increased the product purity to 99.1%.;In addition to production and purification of PHB, monomer production using WEH was also studied. (R)-hydroxyalkanoic acids (R-HAs) are valuable building blocks for the synthesis of fine chemicals and biopolymers because of the chiral center and the two active functional groups. Hydroxyalkanoic acids fermentation can revolutionize the polyhydroxyalkanoic acids (PHA) production by increasing efficiency and enhancing product utility. Modifying the fermentation conditions that promotes the in vivo depolymerization and secretion to fermentation broth in wild type bacteria is a novel and promising approach to produce R-Has. Using Paulownia elongata WEH as a feedstock, the R-3-HB concentration in fermentation broth reached as high as 14.2 g/L after 3 days of batch fermentation and the highest concentration of 16.8 g/L was obtained at day 9. Further investigation indicated that the composition of culture medium contributed to the enhanced R-3-HB production.