Enhancing astaxanthin accumulation in immobilized Haematococcus pluvialis via alginate hydrogel membrane

Immobilized cultivation is anticipated to be effective for enhancing both biomass and astaxanthin accumulation in Haematococcus pluvialis (H. pluvialis). A novel fabrication method of alginate hydrogel membrane (AHM) was introduced for immobilized cultivation of H. pluvialis. This method incorporates cotton gauze into a hydrogel with a low sodium alginate (SA) concentration of 0.5 %, utilizing endogenous calcification. The optimized culture strategy achieved a peak astaxanthin productivity of 256.3 mg·m^-2·d^-1 with an inoculum of 16 g·m^-2 under light irradiation of 300 μmol·m^-2·s^-1 on day 4, resulting in a 70.8 % increase in astaxanthin yield over the control group. Furthermore, a recovery method for H. pluvialis and SA from AHM was explored, using Na₂CO₃ to disintegrate AHM to recover all the microalgal cells and SA with a recovery rate of 88.7 %. Collectively, these findings suggest that immobilized cultivation using AHM is an effective strategy for boosting biomass and astaxanthin accumulation in H. pluvialis.