Production of lipids and carotenoids by yeasts using agroindustrial by-products

Abstract

Lipids and carotenoids are valuable compounds in high demand across various industrial sectors. Due to increasing concerns about sustainable processes, there is interest in alternative sources for the production of these compounds to replace plant extraction and chemical synthesis. Yeasts are microorganisms capable of synthesizing lipids and carotenoids and offer several cultivation advantages. However, only a limited number of yeast species are described for the synthesis of these metabolites, and industrial-scale utilization is still lacking. This study aimed to identify new yeast strains capable of producing lipids and carotenoids using agroindustrial byproducts as substrates. In the first stage, 26 yeast strains were selected, and tests were conducted to evaluate the production of these compounds. Nine strains were selected as oleaginous, exhibiting fatty acid profiles rich in palmitic, palmitoleic, stearic, oleic, and linoleic acids. The yeast Torulaspora maleeae CCMA 0039 showed the highest lipid accumulation (77.7%) in glucose medium, while the previously undescribed oleaginous yeast Exophiala spinifera CCMA 2073 exhibited a lipid content of 35% in pure glycerol. Four strains were identified as carotenogenic. Crude glycerol medium was efficient for lipid and carotenoid production, resulting in greater diversity in fatty acid profiles and higher concentrations of total carotenoids for all tested strains. Cystofilobasidium ferigula CCMA 1623 was identified as promising for further studies, presenting a lipid accumulation of 41.88% and 2.76 µg/mL of total carotenoids under cultivation in crude glycerol. The second stage of the study consisted of optimizing the cultivation parameters of the C. ferigula CCMA 1623 strain using crude glycerol as the carbon source, aiming for concomitant production of lipids and carotenoids. The concentration of yeast extract proved to be a determining factor for the synthesis of these compounds. The optimal condition for lipid and carotenoid accumulation was found to be 1.5 g/L of yeast extract at 26°C and rotation of 140 rpm. Under these conditions, lipid content of 52.59% and 3.03 µg/mL of carotenoids were obtained. The synthesized fatty acid profile consisted mainly of palmitic, stearic, and omega fatty acids (oleic and linoleic). The total carotenoid extract exhibited high antioxidant power in the ABTS, FRAP and DPPH assays. This study enabled the identification of unexplored oleaginous and carotenogenic yeast strains, opening new perspectives for the establishment of fermentation processes using the C. ferigula yeast for simultaneous production of lipids and carotenoids, utilizing crude glycerol as the substrate.