초록
<P><B>Abstract</B></P> <P>The properties of eggshells (EGS) as neutralizing and immobilizing agent were investigated for hydrogen (H<SUB>2</SUB>) production using crude glycerol (CG) by co-culture system. Eggshells of different sizes and concentrations were used during batch and repeated-batch fermentation. For batch and repeated-batch fermentation, the maximum H<SUB>2</SUB> production (36.53±0.53 and 41.16±0.95mmol/L, respectively) was obtained with the EGS size of 33μm<x<SUB>5</SUB> <75μm. Hydrogen production increased with the decreasing size of EGS. Eggshells maintained the fermentation pH (6.00–6.30) and provided immobilization support as confirmed by scanning electron microscopy. As media components, the EGS concentration of 0.25% (w/v) was found to be optimum for maximum H<SUB>2</SUB> production (31.66±0.55mmol/L) and the production profile was comparable to H<SUB>2</SUB> production (32.07±0.92mmol/L) obtained with all media components. In scale-up study with semi-continuous bioreactor (7.5L), almost 1.5-fold increase (in comparison to mono-culture) i.e. 312.12mmol-H<SUB>2</SUB>/L-of medium with 86.65% glycerol utilization was obtained.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Eggshell neutralizing and immobilizing property investigated for H<SUB>2</SUB> production. </LI> <LI> Eggshell maintained fermentation pH (6.0–6.3) and provided immobilization support. </LI> <LI> Maximum H<SUB>2</SUB> for batch (36.5mmol/L) and repeated-batch (41.2mmol/L). </LI> <LI> Semi-continuous production of 312.12mmol-H<SUB>2</SUB>/L at 86.65% glycerol utilization. </LI> <LI> Valorization of eggshells improved H<SUB>2</SUB> and reduced production cost by 85–95%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>