Optimization of Spirulina spp. culture for beta-carotene production

Abstract

The best solvent for beta-carotene extraction of Spirulina was methanol. The optimal conditions for Spirulina isolated from Makkasan pond to produce high yield of beta-carotene were prepared by adjusting the components of Zarrouk medium to contain 1.25 g/l NaNO3, 0.25 g/l K2 HPO4, 0.1 g/l MgSO4 and without K2SO4. An increase of NaCl concentrations in the medium resulted in an increased beta-carotene content whereas growth was obviously decreased. Conditions which yielded the highest beta-carotene content of Spirulina were changing NaCl content from 20 to 30 g/l, adding 40 g/l of NaCl after 4-day growth as well as cultivation of Zarrouk medium containing 40 g/l of NaCl after acclimation to this concentration for 1 week. The optimal light intensity to produce high yield of beta-carotene was found to be 10,000 lux. At the same photosynthetic photon flux density, beta-carotene content of Spirulina was the highest when grown under red light followed by those grown under blue light and white light, respectively. Norflurazon was a strong inhibitor for beta-carotene production whereas diphenylamine was a medium inhibitor and 2,4-dinitrophenol was a weak inhibitor for beta-carotene production. The results of pilot scale outdoor cultivation were similar to those in laboratory scale cultivation. Growth and beta-carotene content were dependent on other environmental factors such as light intensity, temperature and NaCl concentration. Spirulina acquired from pilot scale cultivation was dried. It was found that freeze drying was the best method of drying. Partial purification of beta-carotene was accomplished by only 1 successive run on Silica G-60 column with 97% yield. The optimal storage temperature for Spirulina with respect to beta-carotene loss was -70℃ and 10% sodium metabisulphite slightly protected Spirulina against beta-carotene loss.