This study investigated the effects of eight light sources on photosynthetic bacteria (Rhodopseudomonas palustris) growth and carotenoid content (CD), cultured for 144 h. Light sources were incandescent lamp (IL), halogen lamp (HL), fluorescence lamp (FL), and light-emitting diodes (LEDs) of white (LW), yellow (LY), red (LR), blue (LB), and green (LG). Dark condition served as the control. Under around 2000 lux, light sources ranked greatest to least bacterial growth effect were (LB = IL) > FL > LW >= HL >= LR >= (LG = LY = DK). Ranking effect on CD content was LB > IL >= LY >= (HL = LR = LG) >= LW >= DK >= FL. Energy efficiency for bacterial growth was LB > LW > LY > IL > LG > HL > FL > LR. CD productivity ranking was LB > LY > LW > LG > IL > HL > LR > FL. Results revealed that LB saved 75% energy and increased CD productivity by 348% compared with IL. (C) 2012 Elsevier Ltd. All rights reserved.