Abstract
Introduction: Green microalgae contain a wide array of valuable metabolites that can
potentially attract numerous biomanufacturing businesses. Among these microalgae,
Haematococcus pluvialis, a unicellular freshwater microalga belonging to the
Chlorophyceae class, is prevalent in numerous aquatic environments worldwide. It has
gained recognition as the most abundant and auspicious reservoir for the industrial-scale
synthesis of natural astaxanthin. The effects of γ-aminobutyric acid (GABA) (0 and
0.0001 g/L) on Haematococcus pluvialis different light condition were investigated in
order to find the best inducer and suitable light type (white, blue, and red light) for
maximizing the photosynthesis efficiency and low-cost production.
Materials & methods: Microalgal cells, after growth phase, were subjected to the
different treatments and cell growth rate, chlorophyll, carotenoids, total astaxanthin
content, and the expression of some involved genes in astaxanthin biosynthesis pathways
(psy, lcy, bkt2) were measured.
Results: The results showed that the blue light increased cell division and growth
efficiency (2.64-fold) and red light increased biosynthesis and accumulation of astaxanthin
(94.4 mg/g). Additionally, using GABA enhanced the cell growth and astaxanthin
production. GABA under red light resulted to a significantly higher accumulation of
astaxanthin compared to white and blue light, although it had a lower cell growth rate and
division. Gene expression results also indicated that GABA significantly induces psy and
pds genes under blue and red light.
Conclusion: Collectively, our findings offer a coordinated approach to enhance the
coproduction of astaxanthin by using the combination of red illuminate and GABA which
influences on cell proliferation and astaxanthin synthesis in H. pluvialis.
