Tailored enzymatic treatment of Chlorella vulgaris cell wall leads to effective disruption while preserving oxidative stability

The green microalgae Chlorella vulgaris is a source of valuable nutrients, whose bioaccessibility is limited by the structurally complex cell wall. Enzymatic degradation of the cell wall represents a remarkable alternative to mechanical treatments due to its mildness and specificity. This work aimed to define an optimal combination of enzymes to increase the lipid and protein bioaccessibilities of C. vulgaris cells while preserving oxidative stability. Among the tested enzymes, chitinase, rhamnohydrolase, and galactanase caused the highest release of microalgae cellular material. Treatment with this enzymatic combination produced a slight increase in protein bioaccessibility, from 49.2% +/- 3.9% to 58.7% +/- 3.5%, but no increase in lipid bioaccessibility in comparison to the control. High-pressure homogenization (HPH) led to 61.8% +/- 2.6% lipid and 59.8% +/- 1.8% protein bioaccessibilities. Cell integrity was preserved after enzymatic treatment, while the mean particle size was reduced from 5 to 2 mu m after HPH. Oxidative stability was maintained over 3 months of accelerated shelf life in untreated and enzymatically treated C. vulgaris biomass while HPH caused drastic instability and off-flavour formation. Although more work is needed to optimise the enzymatic treatment to maximise the nutrient bioaccessibility, the presented process was successful in preserving lipid quality.