Growth,vitamin B12, and photopigment formations of Rhodopseudomonas sphaeroides S growing on propionate media under dark and light conditions

Summary The effects of light illumination and dissolved oxygen concentration (DO) on the growth characteristics of Rhodopseudomonas sphaeroides S and intracellular accumulations of vitamin B₁₂ and photopigments were studied in continuous cultures of aerobic-dark (S-1, DO>5 mg l^–1), aerobic-light (S-2, DO>5 mg l^–1, 4.5 klux), microaerobic-light (S-3, DO0,4.5 klux) and anaerobic-light (S-4, 4.5 klux) conditions using propionate media. Growth yields from propionic acid determined in S-3 and 4 were 1.5 to twofold greater than in S-1 and 2. Carbon dioxide evolution observed in S-3 and 4 was 0.05 to 0.1 times that in S-1 and 2. Overall carboxylase activity was maximal in S-4. Intracellular accumulations of bacteriochlorophyll and carotenoid were maximal in S-4, followed by S-3 and almost nil in S-1 and 2. The high growth yields observed in S-3 and 4 could be accounted for the high level of activity of carbon dioxide fixation and by the additional or effective utilization of light energy.Intracellular accumulation of vitamin B₁₂ in S-2, 3 and 4 was 1.5 to 1.8 times that in S-1. The maximum content of the vitamin was 74 g-B₁₂ g-cell^–1. The maximum productivity of vitamin B₁₂, g-B₁₂ l^–1 h^–1, was 6.6 in S-3 since specific growth rate, growth yield and the vitamin content of the cells were maximal in S-3.