Effects of growth medium composition, iron sources and atmospheric oxygen concentrations on production of luciferase-bacterial magnetic particle complex by a recombinant Magnetospirillum magneticum AMB-1

Growth conditions for mass production of luciferase-bacterial magnetic particles (BMPs) by a recombinant Magnetospirillum magneticum AMB-1 were investigated in a pH-regulated fed-batch culture system. Enrichment of growth medium with L-cysteine, yeast extract and polypeptone enhanced both bacterial growth and BMP production. The presence of L-cysteine in the medium was useful for induction of cell growth. Strict anaerobic conditions led to a prolonged lag phase and limited the final cell density. Trace oxygen enhanced cell growth with increasing BMP production. As iron sources, ferrous sulfate and ferric gallate dramatically enhanced BMP yield as compared with ferric quinate, an iron chelate conventionally used. The optimized conditions increased cell density to 0.59 ± 0.03 g cell dry weight/liter and BMP production to 14.8 ± 0.5 mg dry weight/liter in fed-batch culture for four days.