Influence of light intensity, temperature and CO₂ concentration on growth and lipids in green algae and cyanobacteria.

Effects of the environmental variables such as light intensity (Vmol photons m⁻² S⁻¹), temperature (*C) and CO₂ concentration (ppm) on chlorophyll, total soluble proteins and lipids were studied in selected microalgal strains from Chlorophyceae (Chlamydomonas sp., Scenedesmus sp., Chlorella sp., Kirchneriella sp.) and cyanobacteria (Nostoc sp.1, Anabaena sp., Nostoc sp. 2, Cylindrospermum sp.). Cultures were grown under controlled conditions at the National Phytotron Facility, Indian Agricultural Research Institute (IARI), New Delhi. Our results showed that chlorophyll concentration enhanced with increased C0₂. Chlorella exhibited the highest chlorophyll at 850 ppm CO₂ and 28*C; for Chlamydomonas it was at 78 μmol photons m⁻² S⁻¹ light intensity. In Cylindrospernum, total soluble proteins decreased with enhanced C0₂, and were highest at 18*C. In Anabaena, a light intensity of 65 μmol photons m⁻² S⁻¹ was best for maximum total soluble proteins. In Chlorella, CO₂ @ 850 ppm was most suited for maximum lipid accumulation. In Kirchneriella, increase in temperature, from 18*C up to 370C, increased total lipids; the highest was at 28'C. In Chlamydomonas, the light intensity of 78 μmol photons m⁻² S⁻¹ was optimum for lipid accumulation and the maximum total lipids was 30.8 (% dry wt.).