Microalgae digestate effluent as a growth medium for Tetraselmis sp. in the production of biofuels

This study investigated an alternative nutrient source arising from anaerobically digested Tetraselmis sp. effluent (MDE) as a nutrient feed stock to form a closed loop nutrient system. To determine MDE suitability the following factors were observed: growth, lipid content, and the bacterial diversity. MDE was diluted according to the concentration of NH4+ content (20, 40, 60, 80 mg/L) and compared against F/2 medium a standard medium for Tetraselmis sp. The growth rate on the MDE medium was not as rapid as the F/2 medium and the less diluted MDE correlated (R2) with lower total lipid contents (R2, 0.927), additionally acyl carrier proteins (ACP) gene expression rates displayed lower gene expression within MDE treatments. Lastly, higher concentrations of MDE were correlated with a higher bacterial diversity throughout the investigation. The suitability of MDE as a nutrient supplement for the production of Tetraselmis sp. biomass and lipid is feasible.