Enzymatic extraction of <i>Spirulina</i> biomass for the cultivation of the oleaginous yeast <i>Lipomyces starkeyi</i>

Microalgae and oleaginous yeasts are emerging as promising biofuel sources. Microalgae fix carbon dioxide through photosynthesis and can contribute to oil production, whereas oleaginous yeasts, though dependent on external nutrients, yield higher amounts of oil with a fatty acid profile akin to that of vegetable oils. This makes them attractive alternatives for lipid production. Herein, we describe a biofuel-production system in which an oleaginous yeast was cultured using a photosynthetic microalgal extract as the primary medium substrate for producing oleaginous fats. Industrially cultivated Spirulina (Arthrospira) was selected as the model microalga, and Lipomyces starkeyi JCM 5995 as the model oleaginous yeast. The Spirulina extract was prepared as the primary medium substrate, and the growth and lipid productivity of L. starkeyi were evaluated in glucose-supplemented Spirulina extract. Pancreatin, in addition to Spirulina, increased the efficiency of organic carbon extraction, doubling the yield. Extraction efficiency was further optimized by varying pancreatin content, heating temperature, and reaction time. Glucose supplementation was essential for L. starkeyi cultivation; in a culture test using the Spirulina extract supplemented with glucose, both growth and lipid productivity of L. starkeyi were comparable to those achieved with a conventional yeast extract – malt extract medium. Overall, our proposed system represents a novel strategy for cultivating oleaginous yeasts using Spirulina extract, offering a potentially sustainable alternative to conventional feedstocks and advancing industrial biofuel production.