3.4. Effect of each metal ion on ethanol production
Filamentous growth has been previously observed in Z. mobilis
fermentation due to the effects of osmotic pressure, ionic stress,
increased phosphate levels [24] and calcium ions [25,26]. Fig. 3
shows the effect of metal ions on ethanol production by Z. mobilis.
In case of the addition of 1 g/L of Mg2+ or Al3+, 49.5 g/L of ethanol
was produced after 24 h of incubation. This value was the same
as the control at initial glucose concentration of 100 g/L. However,
the addition of 1 g/L of Ca2+ decreased the ethanol production to
43.7 g/L and the addition of 1 g/L of Fe2+ prevented the ethanol
production at initial glucose concentration of 100 g/L. The results
indicated that the growth inhibition effects of Z. mobilis were
observed in addition of 1 g/L of Fe2+ and Ca2+. Ruanglek et al.
[15] observed that mineral salts such as calcium chloride could
inhibit growth of Z. mobilis, while Cheng et al. [27] reported
that inhibitory substances such as Fe, Zn and Cd leads to growth
inhibition of Z. mobilis. In this experiment, these results suggest
that the ethanol production was not observed in SSF due to the
3.4. Effect of each metal ion on ethanol productionFilamentous growth has been previously observed in Z. mobilisfermentation due to the effects of osmotic pressure, ionic stress,increased phosphate levels [24] and calcium ions [25,26]. Fig. 3shows the effect of metal ions on ethanol production by Z. mobilis.In case of the addition of 1 g/L of Mg2+ or Al3+, 49.5 g/L of ethanolwas produced after 24 h of incubation. This value was the sameas the control at initial glucose concentration of 100 g/L. However,the addition of 1 g/L of Ca2+ decreased the ethanol production to43.7 g/L and the addition of 1 g/L of Fe2+ prevented the ethanolproduction at initial glucose concentration of 100 g/L. The resultsindicated that the growth inhibition effects of Z. mobilis wereobserved in addition of 1 g/L of Fe2+ and Ca2+. Ruanglek et al.[15] observed that mineral salts such as calcium chloride couldinhibit growth of Z. mobilis, while Cheng et al. [27] reportedthat inhibitory substances such as Fe, Zn and Cd leads to growthinhibition of Z. mobilis. In this experiment, these results suggestthat the ethanol production was not observed in SSF due to the
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