A new medium was formulated for mass production of Spirulina sp. by incorporating selected nutrients of the standard Zarrouk's medium (SM) and other cost-effective alternative chemicals. This newly formulated medium (RM6) contains single super phosphate (1.25 gl(-1)), sodium nitrate (2.50gl(-1)), muriate of potash (0.98 gl(-1)), sodium chloride (0.5gl(-1)), magnesium sulphate (0.15 gl(-1)), calcium chloride (0.04g(-1)), and sodium bicarbonate (commercial grade) 8 gl(-1). The alga was grown in an illuminated (50pmolphotons m(-2) s(-1) white light) growth room at 30+ 1 degrees C. Maximum growth rate in terms of dry biomass, chlorophyll and proteins in SM was recorded between 6 and 9 days of growth and values were 0.114, 0.003 and 0.068 as compared to 0.112, 0.003 and 0.069 mg ml(-1) d(-1) in RM6,. No significant differences were observed in the protein profiles of Spirulina sp. grown in both the media. From the scale up point of view, the revised medium was found to be highly economical, since it is five times cheaper than Zarrouk's medium. (c) 2006 Elsevier Ltd. All rights reserved.