Poly(3-hydroxybutyrate) production using supplemented corn-processing byproducts through Cupriavidus necator via solid-state fermentation: Cultivation on flask and bioreactor scale

The widespread adoption of Poly(3-hydroxybutyrate) (PHB) encounters challenges due to its higher production costs compared to conventional plastics. To overcome this obstacle, this study investigates the use of low-cost raw materials and optimized production methods. Specifically, food processing byproducts such as corn germ and corn bran were utilized as solid substrates through solid-state fermentation, enriched with molasses and cheese whey. Employing the One Factor at a Time technique, we examined the effects of substrate composition, temperature, initial substrate moisture, molasses, and cheese whey on PHB production at the flask scale. Subsequently, experiments were conducted at the bioreactor scale to evaluate the influence of aeration. In flask-scale experiments, the highest PHB yield, reaching 4.1 (g/kg Initial Dry Weight Substrate) (IDWS) after 72 hours, was achieved using a substrate comprising a 1:1 mass ratio of corn germ to corn bran supplemented with 20 % (v/w) cheese whey. Furthermore, PHB production in a 0.5-L packed-bed bioreactor yielded a maximum of 8.4 (g/kg IDWS), indicating a more than 100 % increase in yield after 72 hours, with optimal results achieved at an aeration rate of 0.5 l/(kg IDWS. h).