A novel concept using the macroalgae Laminaria digitata as substrate to grow heterotrophically microalgae species to be used as fish feed supplement is investigated in the present study. Enzymatic hydrolysis of the macroalgae was performed to release the sugars present in the biomass. The hydrolysate was then used as culture medium and nutrient source to grow heterotrophically three different microalgae species, namely Chlorella protothecoides, Chlorella vulgaris and Chlorella sorokiniana, identified as valuable sources of proteins. Due to its faster growth rates, C. protothecoides was selected for further cultivation in batch reactors and its protein content and amino acid composition were measured. At the end of the process the biomass production reached 10.68 ± 1.33 g L− 1with a total protein accumulation of 41.77 ± 1.82% (dry weight basis) and a protein yield of 0.17 ± 0.06. Moreover, the essential amino acids score at the end of the experiment was 6 times greater than for the original content of the macroalgae hydrolysate which was used as substrate for the microalgae cultivation. Therefore, this study reveals the potential of macroalgae hydrolysate as culture medium for microalgae cultivation and it opens possibilities for the development of future strategies to optimize the microalgae production processes.
- Macroalgae hydrolysate
- Fish feed