초록
<P><B>Abstract</B></P> <P>This study investigated the potential of hydrogen and volatile fatty acid coproduction from two steps dark fermentation with dilute acid treatments of the residual slurry after 1st step fermentation. Sweet sorghum stalks (SS) was used as substrate along with <I>Clostridium thermosaccharolyticum</I> as production microbe. Residual lignocelluloses after 1st step fermentation were treated for 1 h by sulfuric acid concentration of 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5% (w/v) with different reaction temperature of 120, 90 and 60 °C were studied. The optimum severity conditions for the highest yield of products found from the treatment acid concentration of 1.5% (w/v) at 120 °C for 10 g/L of substrate concentration. Experimental data showed that two-step fermentation increased 76% hydrogen, 84% acetic acid and 113% of butyric acid production from single step. Maximum yields of hydrogen, acetic acid and butyric acid were 5.77 mmol/g-substrate, 2.17 g/L and 2.07 g/L respectively. This two-step fermentation for hydrogen and VFA production using the whole slurry would be a promising approach to SS biorefinery.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>C. thermosaccharolyticum</I> was used as production microbe for hydrogen fermentation. </LI> <LI> Acid treatment was performed after 1st step fermentation followed by 2nd step. </LI> <LI> Higher soluble sugar in sweet sorghum stalks consumed in 1st step and more sugar released by acid treatment. </LI> <LI> Higher acid concentration released more sugar along with inhibitor furfural and HMF. </LI> <LI> At lower temperature more acid was needed to release more soluble sugar for fermentation. </LI> </UL> </P>