Valorization of Eucheuma denticulatum as a renewable feedstock for PHA production

The high cost of microbial fermentation substrates has long constrained the commercialization of polyhydroxyalkanoate (PHA) production. To address this challenge, recent studies have explored renewable resources such as macroalgae, which offer promising low-cost alternatives. This study investigated Eucheuma denticulatum , a previously underutilized red macroalga abundant in the Philippines, as a substrate for PHA fermentation through hydrolysis and microbial conversion. The acid hydrolysis conditions, including biomass loading, acid concentration, and incubation time, were optimized to produce hydrolysates with high total reducing sugar (TRS) concentrations. The optimal hydrolysis conditions to maximize TRS concentration were 20% w/v biomass loading, 0.15 N acid concentration, and 30-min incubation time, which produced a hydrolysate with a TRS concentration of 44.60 g/L. In terms of TRS yield, the optimal conditions were found to be 10% biomass loading, 0.15 N acid concentration, and 30-min incubation time. After removing fermentation inhibitors by subsequent overliming and activated carbon treatment, the sugars in the hydrolysate were converted into PHA by Cupriavidus necator KCTC 2649 via fermentation. The maximum estimated PHA concentration obtained was 2.41 g/L after 24 h. These results demonstrate the feasibility of E. denticulatum -derived hydrolysates as a sustainable substrate for bioplastic production, offering a promising alternative to fossil-based feedstocks. • Fermentable sugars can be obtained from Eucheuma denticulatum via dilute acid hydrolysis. • Biomass loading drives TRS yield most, followed by acid concentration • Hydrolysates from E. denticulatum can serve as substrate for PHA production by C. necator KCTC 2649. • Overliming and activated carbon treatment of hydrolysates enhances 24 h PHA production by C. necator .