초록
<P><B>Abstract</B></P> <P>The synergistic effects and optimization of pH, carbon-to-nitrogen ratio (C/N), and light intensity (<I>I</I>) on the photo-fermentative hydrogen production of <I>Rhodobacter sphaeroides</I> 158 DSM and light conversion efficiency have been investigated under different conditions of pH (6.5–8); C/N (15–35); and light intensity (35–185 W m<SUP>−2</SUP>). Response surface methodology (RSM) and Box-Behnken experimental design (BBD) were used to identify the optimum values of the three key parameters of pH, C/N, and <I>I</I>, based on the impact on hydrogen production potential (HPP), hydrogen production rate (HPR), and light conversion efficiency η . With desirability value of 0.91, the optimum values of 7.4, 27.5, and 126 W m<SUP>−2</SUP> were identified for pH, C/N, and <I>I</I> respectively, with HPP, HPR and η reaching 960 mL L<SUP>−1</SUP>, 41.74 mL L<SUP>−1</SUP> h<SUP>−1</SUP>, and 0.31 respectively. Regression analysis indicated a good fit between experimental and model data. The study showed that both C/N ratio and <I>I</I> have crucial and significant effect on the HPP, HPR and η , followed by pH, the synergistic effect of pH–<I>I</I> and C/N <I>I</I> on the light conversion efficiency ( η ) was significant while pH C/N was insignificant. The results and analysis obtained could be very useful for better optimizing the photo-fermentative hydrogen production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Response of biohydrogen production to various levels of pH, C/N, and <I>I</I> was assessed. </LI> <LI> The optimal conditions of pH, C/N, and <I>I</I> were 7.4, 27.5, and 126 W m<SUP>−2</SUP> respectively. </LI> <LI> Responses of HPP, HPR, and η were 960 mL L<SUP>−1</SUP>, 41.7 mL L<SUP>−1</SUP>.h<SUP>−1</SUP>, and 0.31 respectively. </LI> <LI> Analysis reveals a synergy between C/N (or pH) and <I>I</I> for only η . </LI> <LI> Optimizing C/N ratio and <I>I</I> appear to be critical in achieving higher HPP, HPR, and η . </LI> </UL> </P>