초록
<P><B>Abstract</B></P> <P>Co-fermentation of carbon-rich and nitrogen-rich feedstocks with suitable carbon to nitrogen (C/N) ratios is commonly considered as a viable way to enhance biological hydrogen production. In this study, cassava residue (C/N ratio=29.1) and swine manure (C/N ratio=8.6) were mixed and subject to microwave-assisted acid hydrothermal pretreatment. The resulting hydrolysates were used for subsequent dark hydrogen fermentation. However, the mixture with a C/N ratio of 15.1 resulted in the lowest hydrogen yield potential of 107.8mL/g volatile solid (VS). Comparatively, the mono-fermentation of cassava residue exhibited the highest hydrogen yield potential of 145.6mL/g VS and a peak hydrogen production rate of 8.2mL/g VS/h. The modified Gompertz model was employed for kinetic analysis, and suggested that the lag-phase time and peak time of hydrogen fermentation exhibited a significantly positive linear correlation with increased C/N ratios. Reducing sugars analysis indicated that pretreatment of mixed cassava residue and swine manure led to a decrease of total sugar yield by 7.2–10.5% due to the Maillard reactions between hydrolyzed sugars and amino acids. A reaction mechanism based on glucose and arginine was proposed to elucidate the Maillard interactions between carbonyl group (CO) and amino group (NH<SUB>2</SUB>), which was responsible for the overall sugar loss. The findings of this study suggested that pretreatment for mixed carbohydrate-rich and protein-rich feedstocks needs to be optimised to avoid unexpected fermentable sugars loss.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cassava residue (CR)/Swine manure (SM) were mixed for microwave acid pretreatment. </LI> <LI> Mono-fermentation of CR exhibited the highest hydrogen yield of 145.6mL/g VS. </LI> <LI> Mixed CR/SM resulted in the lowest hydrogen yield (107.8mL/g VS) due to sugar loss. </LI> <LI> Pretreatment of mixed CR/SM led to decrease of total sugar yield by 7.2–10.5%. </LI> <LI> Reactions between carbonyl (CO) and amino group (NH<SUB>2</SUB>) resulted in sugar loss. </LI> </UL> </P>