초록
<P><B>Abstract</B></P> <P> <I>Escherichia coli</I> growth and H<SUB>2</SUB> production were followed in the presence of heavy metal ions and their mixtures during glycerol or glucose fermentation at pH 5.5–7.5. Ni<SUP>2+</SUP> (50 μM) with Fe<SUP>2+</SUP> (50 μM) but not sole metals stimulated bacterial biomass during glycerol fermentation at pH 6.5. Ni<SUP>2+</SUP>+Fe<SUP>3+</SUP> (50 μM), Ni<SUP>2</SUP> +Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> (20 μM) and Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> (20 μM) but not sole metals enhanced up to 3-fold H<SUB>2</SUB> yield but Cu<SUP>+</SUP> or Cu<SUP>2+</SUP> (100 μM) inhibited it. At pH 7.5 stimulating effect on biomass was observed by Ni<SUP>2+</SUP>+Fe<SUP>2+</SUP>+Mo<SUP>6+</SUP>. H<SUB>2</SUB> production was enhanced 2.7 fold particularly by Ni<SUP>2+</SUP>+Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> at the late stationary growth phase. Whereas at pH 5.5 increased biomass was when Fe<SUP>2+</SUP>+Mo<SUP>6+</SUP> or Mo<SUP>6+</SUP> were added. H<SUB>2</SUB> yield was decreased compared with that at pH 6.5, but metal ions again enhanced it. During glucose fermentation at pH 6.5 biomass was increased by the mixtures of metal ions, and 1.2 fold increased H<SUB>2</SUB> yield was observed. At pH 7.5 Ni<SUP>2+</SUP>+Fe<SUP>2+</SUP> increased biomass but Cu<SUP>+</SUP> or Cu<SUP>2+</SUP> had suppressing effect; Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> stimulated H<SUB>2</SUB> production. At pH 5.5 biomass also was raised by Ni<SUP>2+</SUP>+Fe<SUP>2+</SUP>+Mo<SUP>6+</SUP>; H<SUB>2</SUB> yield was increased upon Mo<SUP>6+</SUP> and Mo<SUP>6+</SUP>+Fe<SUP>2+</SUP> or Mo<SUP>6+</SUP>+Fe<SUP>3+</SUP> additions. The results point out the importance of Ni<SUP>2+</SUP>, Fe<SUP>2+</SUP>, Fe<SUP>3+</SUP> and Mo<SUP>6+</SUP> and some of their combinations for <I>E. coli</I> bacterial growth and H<SUB>2</SUB> production mostly during glycerol but not glucose fermentation and at acidic conditions (pH 5.5 and 6.5). They can be used for optimizing fermentation processes on glycerol, controlling bacterial biomass and developing H<SUB>2</SUB> production biotechnology.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ni<SUP>2+</SUP> (50 μM) with Fe<SUP>2+</SUP> (50 μM) stimulated <I>Escherichia coli</I> biomass during glycerol fermentation. </LI> <LI> Ni<SUP>2+</SUP>+Fe<SUP>3+</SUP> (50 μM), Ni<SUP>2</SUP> +Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> (20 μM) and Fe<SUP>3+</SUP>+Mo<SUP>6+</SUP> (20 μM) enhanced H<SUB>2</SUB> yield but Cu<SUP>+</SUP> or Cu<SUP>2+</SUP> (100 μM) inhibited it. </LI> <LI> These effects were dependent on pH and different upon various heavy metals and their mixtures supplementations. </LI> <LI> Enhanced effects were observed for the late stationary growth phase at pH 7.5. </LI> <LI> Some heavy metals and their combinations were important for <I>E. coli</I> biomass and H<SUB>2</SUB> production mostly on glycerol vs glucose and at pH 5.5 and 6.5. </LI> </UL> </P>