Cultivation of Scenedesmus obliquus in liquid hydrolysate from flash hydrolysis for nutrient recycling

Abstract

The production of biofuels from microalgae is associated with high demands of nutrients (nitrogen and phosphorus) required for growth. Recycling nutrients from the residual biomass is essential to obtain a sustainable production. In this work, the aqueous phase obtained from flash hydrolysis of Scenedesmus sp. was used as cultivation medium for a microalga of the same genus, to assess the feasibility of this technique for nutrient recycling purposes. Batch and continuous cultivations were carried out, to determine growth performances in this substrate compared to standard media, and verify if a stable biomass production could be obtained. In continuous experiments, the effect of hydrolysate inlet concentration and of residence time were assessed to optimize nutrient supply in relation to productivity. Results obtained show that nutrient recycling is feasible by treating biomass with flash hydrolysis, and Scenedesmus is capable of recycling large amounts of recovered nutrients.

Techno‐economic analysis of protein concentrate produced by flash hydrolysis of microalgae

“…Our previous studies [19][20][21][22] reported protein extraction from microalgae via bench-scale flash hydrolysis (FH). The FH process has shown to be one of the most efficient approaches in selectively hydrolyzing proteins to peptides and amino acids in short residence times (10 s) using a continuous flow reactor operated at 2808C.…”

Integration of biofuels intermediates production and nutrients recycling in the processing of a marine algae

“…In a previous work, it was shown that Scenedesmus sp. was able to uptake the organic nitrogen forms contained in the medium and use that for growth . However, the capability of up‐taking simple organic nitrogen is species‐dependent, and has therefore to be assessed for the species considered .…”

“…Conversely, flash hydrolysis (FH) has been proven to be a sustainable continuous process that can utilize the wet algal biomass (slurry) at 280°C temperature and very short residence time (9 s) to fractionate macronutrients such as nitrogen and phosphorous while preserving lipids in the solid residue (biofuels intermediates) . The successful realization of short residence times for fractionating algae components (proteins and lipids) would greatly reduce the reactor volume, significantly reduce CAPEX and OPEX, and provides product stream of small peptides and amino acids as a co‐product along with the lipid‐rich solids as biofuels precursors.…”

“…In a recent study carried out by Barbera et al, it was shown that the same hydrolyzate obtained from FH could be used for cultivation of Scenedesmus obliquus , without requiring the addition of any other nutrients . In particular, the growth rate obtained in batch experiments resulted to be higher compared to that in standard medium, due to mixotrophic growth exploiting residual organic carbon molecules in the hydrolyzate.…”

“…In particular, the growth rate obtained in batch experiments resulted to be higher compared to that in standard medium, due to mixotrophic growth exploiting residual organic carbon molecules in the hydrolyzate. In addition, continuous steady‐state production was also obtained under various conditions …”