초록
<P><B>Abstract</B></P> <P>Photofermentative hydrogen production was carried out under outdoor conditions with a <I>Rhodobacter capsulatus</I> strain on molasses, a renewable and sustainable feedstock. An existing photobioreactor design was scaled-up from 9 L to 20 L. The decreased carbon-to-nitrogen (C/N) ratio of 13.0, compared to our previous work, accelerated growth and resulted in a reduced lag period for hydrogen production as well as higher productivities in the exponential phase. However, the low C/N ratio also promoted a high optical density due to growth, limiting light transmission. Still, the maximum productivity was found as 0.47 mol H<SUB>2</SUB>/(m<SUP>3</SUP>·h), significantly higher than our result with the smaller reactor volume. High rates of production could not be maintained presumably due to the combined effects of cloudy periods, the aforementioned C/N ratio and decreasing pH. These results suggest that the scale-up was successful and there is potential for further improvement using optimal C/N ratio and cell concentration values.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Outdoor photofermentative hydrogen production carried out from diluted molasses. </LI> <LI> An existing photobioreactor design was scaled-up to 20 L from 9 L. </LI> <LI> The low C/N ratio promoted growth and reduced the lag time for hydrogen production. </LI> <LI> Adverse weather conditions and high optical density decreased productivity. </LI> <LI> Maximum productivity was 0.47 mol H<SUB>2</SUB>/(m<SUP>3</SUP>·h). </LI> </UL> </P>