Culture of Bacillus subtilis and Saccharomyces cerevisiae from byproducts of the enzymatic extraction of Atlantoraja castelnaui oil

The growing trend in global fish consumption has led to the generation of a large amount of waste and byproducts with negative economic and environmental impacts. The production of fish oil from fish processing residues seems to be a sustainable and future opportunity to provide valuable fatty acids for animal and human consumption. In parallel, this alternative valorization of fish waste has increased the demand to explore sustainable extraction methods. Enzymatic hydrolysis is an efficient, rapid and reproducible method for the extraction of oils from fish guts, producing an aqueous phase rich in proteins and soluble compounds. In this work, a highly soluble aqueous phase obtained from the enzymatic extraction of the liver oil of the ray Atlantoraja castelnaui was tested as a source of nutrient for the growth of Bacillus subtilis and Saccharomyces cerevisiae. Culture media were supplemented with the aqueous phase at a final concentration of 10 mg ml-1 total protein. The growth pattern and biomass yield of yeasts cultured in yeast extract peptone-dextrose (YPD) medium did not show statistically significant differences (p: 0.05) with the diluted medium and the aqueous fraction (AF) supplemented medium. Similar results were obtained for B. subtillis and its positive control in Luria Bertani (LB) medium. In both cases, the ability of these inexpensive media to support the growth of microorganisms was demonstrated. Results suggested that the remaining aqueous phase of the discards from A. castelnaui oil production can be used as an alternative substrate for microorganism culture purposes. In this way, a residue destined for disposal could become a product with added value achieving a good result in the context of circular economy.