Conference article

The biotechnological production of poly-3-hydroxybutyrate (PHB) from crude glycerol obtained during the biodiesel production was techno-economically assessed. For the fermentation process; two different strains; Cupreavidus necator and Bacillus megaterium were considered. Moreover; three downstream processes for PHB separation and purification were analyzed. Thus; in total six biotechnological schemes to transform the crude glycerol obtained in the biodiesel industry were compared. Each biotechnological scheme considered five main process stages namely: (i) glycerol purification; (ii) glycerol fermentation to PHB; (iii) mass cell pretreatment; (iv) PHB isolation; and (v) PHB purification. Aspen Plus and Aspen Icarus were used for the processes simulation and for the economic assessment; respectively. During the processes simulation the crude glycerol stream was purified from 60 to 98 wt %; and the fermentation process was considered in two continuous stages where mass cell growth and PHB accumulation occurred; respectively. Also; the three downstream processes were based on: (i) heat pretreatment and chemical-enzymatic digestion; (ii) high pressure homogenizer and solvent extraction; and (iii) alkaline pretreatment and chemical-enzymatic digestion. Economic results showed that the best technological scheme uses C. necator for the fermentation stage; with a heat pretreatment and enzymatic-alkaline digestion for the downstream process.

Glycerol fermentation; PHB production; Process simulation; Process assessment