초록
<P><B>Abstract</B></P> <P>We studied the influence of initial pH on hydrogen (H<SUB>2</SUB>) production using permeate from scotta (a partially deproteinized cheese whey from ricotta production) as substrate (51 g L<SUP>−1</SUP> lactose). Dark fermentation was carried out at 35 °C in laboratory batch reactors, in an unbuffered system. Hydrogen production and metabolite (volatile fatty acids, ethanol, and lactic acid) evolution during a 96-h period were monitored in reactors with initial pH varying in the range 4–10. In all reactors, H<SUB>2</SUB> production started only when pH fell below 6. However, it was much higher (+31%) in the reactors with initial alkaline pH. We conclude that H<SUB>2</SUB> production occurs only at acidic pH values, but initial alkaline pH values increase the overall H<SUB>2</SUB> production in dark fermentation of lactose-rich substrates.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We studied the pH effect on H<SUB>2</SUB> production in dark fermentation of scotta permeate. </LI> <LI> At the start of fermentation pH decreased or increased, regardless of its initial value. </LI> <LI> Hydrogen production always started when the pH of the fermentation broth was below 6. </LI> <LI> However, H<SUB>2</SUB> production rate and yield were much higher when initial pH was alkaline. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>