초록
<P><B>Abstract</B></P> <P>Glycerol is a highly available by-product generated in the biodiesel industry. It can be converted into higher value products such as hydrogen using biological processes. The aim of this study was to optimize a continuous dark fermenter producing hydrogen from glycerol, by using micro-aerobic conditions to promote facultative anaerobes. For that, hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) was continuously added at low but constant flow rate (0.252 mL/min) with three different inlet concentrations (0.2, 0.4, and 0.6% w/w). A mixture of aerobic and anaerobic sludge was used as inoculum. Results showed that micro-oxidative environment significantly enhanced the overall hydrogen production. The maximum H<SUB>2</SUB> yield (403.6 ± 94.7 mmolH<SUB>2</SUB>/molGly<SUB>consumed</SUB>) was reached at a H<SUB>2</SUB>O<SUB>2</SUB> concentration of 0.6% (w/w), through the formate, ethanol and butyrate metabolic pathways. The addition of H<SUB>2</SUB>O<SUB>2</SUB> promoted the development of facultative anaerobic microorganisms such as <I>Klebsiella</I>, <I>Escherichia-Shigella</I> and <I>Enterococcus</I> sp<I>.</I>, likely by consuming oxygen traces in the medium and also producing hydrogen. Despite the micro-oxidative environment, strict anaerobes (<I>Clostridium</I> sp.) were still dominant in the microbial community and were probably the main hydrogen producing species. In conclusion, such micro-oxidative environment can improve hydrogen production by selecting specific microbial community structures with efficient metabolic pathways.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen production in micro-oxidative environment was investigated. </LI> <LI> A maximum hydrogen yield of 403.6 ± 94.7 mmolH<SUB>2</SUB>/molGly<SUB>consumed</SUB> was reached. </LI> <LI> H<SUB>2</SUB>O<SUB>2</SUB> injection favoured metabolic pathways related to hydrogen production. </LI> <LI> The addition of H<SUB>2</SUB>O<SUB>2</SUB> promoted the development of facultative anaerobic microorganisms. </LI> <LI> Strict anaerobes dominated the microbial community despite the microoxidative environment. </LI> </UL> </P>