Growing Algae-Based DHA More Efficiently Using Food Byproduct Fermentation Fluid

This lab study explored a more efficient way to grow the marine microorganism Schizochytrium limacinum, which is used commercially to produce DHA (an omega-3 fatty acid) without fish. Instead of standard sugar-based feed, researchers used a nutrient-rich liquid leftover from ‘dark fermentation’ of organic waste, which contains short-chain acids the organism can use as fuel.

The problem with this waste-derived feed is that it’s diluted, meaning large volumes are needed to supply enough nutrients, which in turn dilutes the cell culture and slows down production. To solve this, researchers tested a ‘cell retention’ system that keeps the microbial cells in the tank using a membrane filter while continuously flushing in fresh feed and removing spent liquid.

The cell-retention approach produced 4.4 times more biomass than a standard repeated-feeding method (33 grams vs 7.5 grams) and boosted DHA output roughly eightfold (1.9 g/L vs 0.24 g/L). The organism preferentially consumed acetate and butyrate from the waste stream over other acids. The technique also removed a majority of nitrogen and phosphate from the waste effluent as a side benefit.