Second‐Generation Polyhydroxybutyrate Production From Pretreated Corn Lignocellulosic Fraction as a Strategy to Repurpose by Products From the Corn‐Processing Chain

ABSTRACT

Lignocellulosic residues are non‐cost, non‐edible, renewable feedstocks that can be used in polyhydroxybutyrate (PHB) production. PHB is a bioplastic synthetized by microorganisms, formed intracellularly under stressful growth conditions; however, its production costs are high, representing the major drawback for fossil‐based plastics replacement. The use of lignocellulosic waste in PHB production can help to reduce its costs. Therefore, this work aimed to optimize the second‐generation (2G) PHB production process from the lignocellulosic corn fraction (LCF). The LCF is a lignocellulosic by‐product generated during first‐generation (1G) PHB production from milled corn ( Zea mays ). A novel integrated citric acid pretreatment followed by enzymatic hydrolysis in just one‐pot was employed. Two cellulolytic enzymes from a highly productive strain were employed at an enzyme loading of 11.64 mg β‐glucosidase/g substrate and 0.6 mg cellulase/g substrate. These enzymes concentrations were employed in a hydrolysis assay in an agitated tank, reaching 47.37 g/L of total sugars (95.71% of glucose). This hydrolysate was employed as a low‐cost carbon source for 2G PHB production by Cupriavidus necator LPB2327. In the optimized condition, 8.90 g/L of dry cell weight (DCW), and 7.64 g PHB/L (85.89% PHB accumulation) were achieved. Overall, high product yields of 0.254 g PHB/g substrate, and 0.127 g PHB/g LCF were obtained. These results indicate the feasibility of using this integrated approach for 2G PHB production within a corn biorefinery strategy.