Exploring lipids and citric acid production by Yarrowia lipolytica in lignocellulosic biomass hydrolysate-mimicking media: Effect of cultivation operation modes

This study explores the potential of two strains of Yarrowia lipolytica, W29 and NCYC 2904, to produce lipids-rich biomass and citric acid under batch, fed-batch, and repeated-batch cultivation in a eucalyptus bark hydrolysate-mimicking medium (EH-MM). Considering the variability in lignocellulosic hydrolysates composition, two EH-MM formulations, differing in glucose, xylose, acetic acid, formic acid, and 5-hydroxymethylfurfural concentration, were evaluated in batch mode. No growth inhibition was observed at 100 g⋅L⁻¹ glucose, but lipids accumulation was highest at 50 g⋅L⁻¹ glucose for both strains. The highest citric acid production (44 g⋅L⁻¹) was achieved with W29 in the most concentrated medium. Fed-batch mode increased lipids content in NCYC 2904 (51 %) and citric acid in W29, whereas repeated-batch enhanced biomass production and lipids titers compared to the other strategies. The highest biomass (66 g⋅L⁻¹) and lipids concentration (25 g⋅L⁻¹) were obtained with NCYC 2904 in two-stage repeated-batch culture, with a C/N ratio of 10 in 1st batch and 75 in 2nd batch. The accumulated lipids were mainly composed of oleic, palmitoleic, and palmitic acids, suggesting their potential as biofuel feedstock. Overall, the results indicate that batch cultivation of W29 for citric acid and two-stage repeated-batch cultivation of NCYC 2904 for lipids are promising strategies for valorizing lignocellulose-derived sugars, underscoring the importance of strain selection and operation mode in biorefinery design.