LIGHT-DEPENDENT PORPHYRIN PRODUCTION BY SUSPENDED AND IMMOBILIZED CELLS OF RHODOBACTER-SPHAEROIDES

This study was undertaken to determine optimum conditions for porphyrin production by suspended and immobilized cells of Rhodobacter sphaeroides. Cell suspensions of R. sphaeroides strain NR3 previously grown photosynthetically excreted large amounts of porphyrins with coproporphyrin III as the major component under anaerobic-light conditions. The most pronounced excretion was found in the presence of 10 mM glycine, 10 mM succinate, and 0.1 mM Mg2+ (or Ca2+) and at pH between 7.5 and 8.0 and a high light intensity (≧ 15,000 lx). The amount of porphyrins produced after 6 d of incubation by cell suspensions with an initial cell dry weight of 0.54 g was 170 μmol·l-1. Extracellular porphyrin formation was severely inhibited by levulinate, 2, 2′-dipyridyl, or chloramphenicol. Immobilization of cells with agar or carrageenan resulted in a marked decrease in the formation rate. However, intermittent treatment with a growth medium restored the ability of the immobilized cells to produce porphyrins effectively. Agar-immobilized cells in a repeated batch process including the intermittent treatment stage for re-activation produced higher levels of porphyrins than did cell suspension. © 1989.