Reduction of lipids in fish meal prepared from fish waste by a yeast Yarrowia lipolytica

The high lipid content in fish waste is one of the reasons why fish meal made from fish waste is commercially rated as low grade meal. Microorganisms which have the ability to reduce crude lipids from samples of minced fish in solid-state fermentation were screened and a strain of Yarrowia lipolytica showed the highest efficiency for reducing the lipids by 29%. The lipid reduction by this strain was especially affected by the ratio of surface area to the weight in the fermented mince samples and by the water content, suggesting the importance of the oxygen supply. In the fermentation with intermittent mixing during 96 h incubation, reduction efficiency for crude lipids came to 46% but that for protein was less than 1%. With the fermentation, 41.5 g of crude lipids in 1 kg of the minces were estimated to be reduced to 22.4 g, indicating increase of protein content in the final product. Furthermore, the carbonyl value which is an indicator of lipid oxidation was relatively suppressed by the fermentation. These results suggest that the fermentation can improve the quality of fish meal from fish waste which is rich of lipids.