Holistic valorization of sugar streams from forest and agricultural residues towards the production of fatty acids by the dinoflagellate Crypthecodinium cohnii in fed-batch bioreactors

Heterotrophic microalgae have emerged as promising sources of polyunsaturated fatty acids with broad industrial applications. Current research focuses on finding sustainable, cost-effective nutrient sources, including lignocellulosic biomass. In this study, we investigate the lipid accumulation of Crypthecodinium cohnii in fed-batch fermentations using hydrolysates from OxiOrganosolv-pretreated solid pulps and aqueous liquid fractions. The objective was to evaluate different sugars as carbon sources and assess any potential inhibitory effects on productivity. Among the pretreated pulps, ethanol pretreated beechwood exhibited the highest performance, with a docosahexaenoic acid (DHA) content of 38.4 % of total lipids. Liquid fractions effectively supported lipid accumulation, however with a lower DHA content. Finally, a preliminary economic evaluation of wheat straw valorization, selected for high lipid yield (54.6 mg total fatty acids/g of biomass), suggests that profitability can be achieved in plants processing over 200 kg of feedstock/h, with a production cost of less than 160 €/kg of DHA-rich oil. • Successful holistic valorization of biomass hexoses/pentoses for DHA production. • Fed-batch fermentation significantly improved cell growth and lipid accumulation. • Liquid fractions led to higher cell densities but lower DHA content in the oil. • Higher lipid production of 54.6 mg/g of untreated biomass observed in wheat straw. • Profitability achieved in wheat straw plants > 200 kg/h, producing DHA at < 160 €/kg.