Production and recovery of poly-3-hydroxybutyrate bioplastics using agro-industrial residues of hemp hurd biomass.

The present study describes production and recovery of poly(3-hydroxybutyrate) P(3HB) from agro-industrial residues. Production was conducted using Ralstonia eutropha strain with hemp hurd biomass hydrolysates sugars as a carbon source and ammonium chloride as the nitrogen source. Results show that maximum hydrolysis yield of 72.4% was achieved with total sugar hydrolysate concentration (i.e., glucose and xylose) of 53.0 g/L. Sugar metabolism by R. eutropha showed preference for glucose metabolism over xylose. Under optimum conditions, cells can accumulate P(3HB) polymer in quantity up to 56.3 wt% of the dry cell weight. This corresponds to total production of 13.4 g/L (productivity of 0.167 g/L h). Nitrogen source showed no adverse effect on P(3HB) biosynthesis, but rather on cell growth. Among several examined recovery techniques, ultrasonic-assisted sodium dodecyl sulfate (SDS) recovered bioplastic directly from the broth cell concentrate with P(3HB) content of 92%. Number average molecular weights (M_n) of final recovered bioplastic were in the range of 150-270 kDa with polydispersity index (M_w/M_n) in the range of 2.1-2.4.