This project tests up-cycling of food-grade wastes through mixotrophic algal culture. The wastes, which include fish processing waste, vinasse, and whey permeate—the by-products of fishing/aquaculture, distillation, and cheese making—contain high organic and inorganic C, N, and P. Tests with phytoplankton commonly used as aquaculture feeds have shown that the addition of the wastes to the growth medium can augment growth rates and/or biomass yields of some phytoplankton and that the phytoplankton fully remediate the inorganic N and P, and the organic P. However, there are high residual concentrations of organic N that remain inaccessible to the algae.
Tests are currently underway on whether chemical oxidation of the residual N will allow it to be recycled into the culture. Biological remediation is a more attractive alternative, if a second organism that can metabolize the nutrients also produces high-value biomass. This project will test thraustochytrids, heterotrophic protists that are common in marine waters and that are already the focus of active research because of their high quotas of valuable omega-3 fatty acids.
If successful, the project will provide proof of concept for a novel means to reduce the problem of waste disposal in aquaculture, coupling it to production of high-grade feeds/foodstuffs, and thereby reducing fishing pressure on wild stocks of fish.