PRODUCTION OF TETRAPYRROLE COENZYMES BY A METHANOGEN

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A methanogen, Methanosarcina barkeri contains three tetrapyrroles, i.e., Cocontaining corrinoids, Ni-containing factor F_<430> and Fe-containing cytochroms (hemes) which are biosynthesized via 5-aminolevulinic acid(ALA). In this work, the selective formation of these tetrapyrroles and ALA, a potent herbicide were carried out. The results obtained were as follows.1. Effects of Co^<2+>, Ni^<2+>, Fe^<2+> on the selective synthesis of respective tetrapyrroels were examined in batch culture. The increase of Co^<2+> in the medium fixing the low concentrations of Ni^<2+> and F^<2+> in the medium significantly stimulated the extracellular corrinoids syntheses, while F_<430> and heme were kept almost unchanged. Similar stimulative synthesis of extracellular F_<430> or heme was observed as a function of increasing Ni^<2+> or Fe^<2+> in the medium suggesting that the syntheses of these three tetrapyrroles might be regulated with the respective matal. Then, continuous production of tetrapyrroles i … More n a fixed-bed reactor(supporter: porous diatomaceous clay) was carried out a a dilution rate, 10.1 day^<-1>. The effluent discharged from the top of reactor contained the excreted tetrapyrroles whose concentration was depended upon Co^<2+>, Ni^<2+>, Fe^<2+> in the feed medium. The maximum productivies from the roactor(1-1 bases) were 52 m [corrinoids]/day, 24 m[F_<430>]/day and 8 m [heme]/day.2. To accumulate ALA into the culture medium, some ALA analogues were tested as inhibitor of ALA dehydratase. It was found that ALA was accumulated when levulinic acid or 4,6-dioxoheptanoic acid was added, the latted was more effective even at a much lower concentration. It was found that 2-oxoglutarate reacted as a precursor on the formation of ALA indicating that the production ALA increased 83 m from 37 m with the addition of 30 mM of 2-oxoglutarate compared with the control experiment. The continuous productions of ALA from methanol in fixed-bed reactors was tested indicating that the maximum production rate was 400 m/day. Less