Influence of nitrogen sources on growth of thraustochytrids in waste water from the demineralization of cheese whey

Abstract

An experimental design was ued to optimize the growth of two thraustochytrids, (Schizochytrium limacinum PA-968 and Japonochytrium marinum AN-4), on different nitrogen sources (yeast extract, corn steep liquor, ammonium sulphate) supplemented into saline waste water from the demineralization of cheese whey. Yeast extract was found to be the most suitable complex nutrient source. Nitrogen limitation was found to increase the lipid content in shake flask cultures of thraustochytrids by 12.7-22.4% w/w. The maximum total lipid content (79.1% w/w) and docosahexaenoic acid productivity (0.465 g/l per day) were achieved by J. marinum AN-4 in shake flask cultures. Fed-batch cultures of J. marinum AN-4, under conditions of nitrogen limitation, yielded biomass with a lower lipid content (72.1% wt.) but higher docosahexaenoic acid productivity (1.43 g/l per day). These results provide proof of concept that fed-batch cultivation of thraustochytrids, combined with nitrogen limitation, can be an appropriate strategy for the productive use of saline waste water from the dairy industry.

Keywords

• docosahexaenoic acid
• japonochytrium marinum
• nitrogen limitation
• saline waste water
• schizochytrium limacinum