Role of [N2222][Arg] amino acid ionic liquids in the enhancement of biomass in Haematococcus pluvialis via the regulation of reactive oxygen species signals

The slow growth of Haematococcus pluvialis restricts its use for large-scale production of astaxanthin. In this study, [N2222][Arg] amino acid ionic liquids (AAILs) were applied to increase the biomass of H. pluvialis. The maximum biomass concentration and cell count reached 0.98 g L−1 and 165.3 × 104 cells mL−1, respectively. An increase of 38.03% in biomass and 34.31% in cell number was observed following supplementation with [N2222][Arg]. Treatment with [N2222][Arg] resulted in increases in carbohydrate, protein and chlorophyll contents, Fv/fm and the expression levels of genes associated with cell growth. Notably, [N2222][Arg] application triggered reactive oxidative species (ROS) and lateral membrane diffusion and changed the fatty acid composition, which is potentially involved in cell division and growth. Further data indicated that exogenous H2O2 could enhance alga biomass production in the presence of the [N2222][Arg] ionic liquid. Moreover, the accumulation of astaxanthin also increased in H. pluvialis treated with [N2222][Arg]. This study presents a potential method for enhancing the biomass production of H. pluvialis using amino acid ionic liquids and elucidates the role of ROS signalling in the regulation of cell growth.