Optimization of the Dark Fermentation Technique for Hydrogen Production through Supplementation with Ascorbic Acid and/or <scp>l</scp>-Cysteine by <i>Clostridium butyricum</i> CCDBC 11

This study explores the enhancement of biohydrogen production through the addition of oxygen scavengers, ascorbic acid, and l-cysteine during dark fermentation by <i>Clostridium butyricum</i> strain. The supplementation of these compounds significantly reduced the bacterial lag phase and accelerated cell growth, thereby boosting the hydrogen output. Using saccharified corn scrap as the substrate, a maximum cumulative hydrogen yield of 2.20 mol H₂/mol glucose was achieved with 5 mg/L ascorbic acid. This treatment reduced the lag phase by 65.6% and increased the hydrogen yield by 40.9% compared to the control and by 11.4% relative to l-cysteine supplementation alone. Biogas production was quantified via the water displacement method, and hydrogen content was analyzed using gas chromatography. The results indicate that ascorbic acid is a cost-effective and efficient additive for improving the hydrogen yield in dark fermentation processes.