Springer Online Journal Archives 1860-2000
Process Engineering, Biotechnology, Nutrition Technology
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, DO≈0,4.5 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 μg-B12 g-cell−1. The maximum productivity of vitamin B12, μg-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.
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