Algae biocers: astaxanthin formation in sol–gel immobilised living microalgae

Abstract

New biocer materials consisting of the living microalgae cells Haematococcus pluvialis immobilised within modified sol–gel silica layers can produce the metabolic carotinoid dye astaxanthin after being coated on glass then cultivated. The layer stability and viability of the embedded microalgae depends on the preparation, storage, cultivation, stressing and extraction conditions. For example the use of a new optimised culture medium ensures the viability of the immobilised microalgae cells for more than 40 days. The combined application of Fe2+ compounds with NaCl or hydrogen peroxide as stress factors causes a strong increase in astaxanthin formation within the biocer coatings during cultivation. The dye can then be extracted with various organic solvents. When combined with cell-protective additives there is only a moderate decrease in viability after solvent extraction, allowing the immobilised microalgae to be recultivated. In this way the continuous biotechnological production of astaxanthin seems possible in principle.