*Article Crypthecodinium cohnii* **Growth and Omega Fatty Acid Production in Mediums Supplemented with Extract from Recycled Biomass**

**Elina Didrihsone 1,\*, Konstantins Dubencovs 1,2,3, Mara Grube 4, Karlis Shvirksts 4, Anastasija Suleiko 1, Arturs Suleiko 1,2 and Juris Vanags 1,2,3**


**Abstract:** *Crypthecodinium cohnii* is a marine heterotrophic dinoflagellate that can accumulate high amounts of omega-3 polyunsaturated fatty acids (PUFAs), and thus has the potential to replace conventional PUFAs production with eco-friendlier technology. So far, *C. cohnii* cultivation has been mainly carried out with the use of yeast extract (YE) as a nitrogen source. In the present study, alternative carbon and nitrogen sources were studied: the extraction ethanol (EE), remaining after lipid extraction, as a carbon source, and dinoflagellate extract (DE) from recycled algae biomass *C. cohnii* as a source of carbon, nitrogen, and vitamins. In mediums with glucose and DE, the highest specific biomass growth rate reached a maximum of 1.012 h<sup>−</sup>1, while the biomass yield from substrate reached 0.601 g·g−1. EE as the carbon source, in comparison to pure ethanol, showed good results in terms of stimulating the biomass growth rate (an 18.5% increase in specific biomass growth rate was observed). DE supplement to the EE-based mediums promoted both the biomass growth (the specific growth rate reached 0.701 h−1) and yield from the substrate (0.234 g·g−1). The FTIR spectroscopy data showed that mediums supplemented with EE or DE promoted the accumulation of PUFAs/docosahexaenoic acid (DHA), when compared to mediums containing glucose and commercial YE.

**Keywords:** *Crypthecodinium cohnii*; omega-3 fatty acid; biomass recycling; dinoflagellate extract; FTIR spectroscopy
