Research Article: Valorization of the discards from the extraction oil processes of a ray fish (Zearaja flavirostris) liver as a culture media to produce Saccharomyces cerevisiae biomass

The great amount of unutilized rest raw materials in the cartilaginous fish industry led to investigate the possible utilization methods to generate a value-added product. In this study, the residual aqueous fractions of oil extraction processes from the liver of longnose ray (Zearaja flavirostris), were evaluated as a possible replacement for the commercial yeast extract peptone dextrose (YPD) culture medium for Saccharomyces cerevisiae. Oil extraction from the ray livers was carried out by different processes such as enzymatic hydrolysis, cold extraction, and extraction by applying high temperatures. The obtained culture media based on the aqueous fractions from the fish ray livers were compared with an industrial reference media. The pattern of cell growth and biomass yield was similar using both the standard culture medium for YPD as a positive control and the diluted and supplemented with the aqueous fractions obtained by the enzymatic extraction method. The results suggest that these by-product fractions provide an alternative source of carbon (peptides and free amino acids) as well as macro- and microelements for the growth of S. cerevisiae.