Corn or Soybean Oil as the Sole Carbon Source for Polyhydroxybutyrate Production in a Biofuel Biorefinery Concept

The use of polyhydroxybutyrate (PHB) can help diminish fossil chemical dependency because it can partially replace petrochemical plastics due to its biodegradability and similar mechanical properties. However, its production costs are high compared with fossil-based plastics. Alternative carbon sources can be used in the fermentation media because they are renewable and low-cost. Vegetable oils are especially attractive due to their high carbon content, contributing to high production rates per gram of substrate. This work aimed to produce PHB from Cupriavidus necator LPB1421 using either corn or soybean oil as the sole carbon source. Urea was the best nitrogen source, enabling a DCW production of 4.35 g/L (corn oil) and 10.4 g/L (soybean oil). After media optimization, the DCW of corn oil reached 22.13 g/L, with 57.46% PHB accumulation (12.71 g PHB/L), whereas soybean oil led to a DCW of 19.83 g/L, with 54.91% PHB accumulation (10.89 g PHB/L). This media composition was employed in a kinetics assay, revealing similar fermentation parameters among both oils and a yield of 0.2118 g PHB/g for corn oil and 0.1815 g PHB/g for soybean oil. These results open the possibility of integrating PHB production with biofuel manufacturing in a bioethanol/biodiesel biorefinery concept.