A remarkable enhancement in hydrogen production from Clostridium beijerinckii G117 by the co-fermentation of crude glycerol and rice bran hydrolysates.

Clostridium beijerinckii G117 produces hydrogen (∼4400 mL/L) from 15 g/L of native crude glycerol (CG). While increasing the native-CG to 20–80 g/L, strain G117 rejects 34–90% of CG and fails to support a relative enhancement in hydrogen production. Subsequently, to enhance the native-CG assimilation, and hydrogen production from strain G117, various agro-residual hydrolysates (ARH), and several metal-ions have individually tested as media-supplements. Among tested, rice bran hydrolysate (RBH) and ferrous chloride (Fe2+) are selected as media-supplements. By employing RSM-based central composite design, the medium composed of 37.63 g/L CG, 3.65 g/L RBH and 1.11 mM Fe2+ is optimized which results a favorable initial redox potential (−191.0 ± 1.5 mV), higher cellular growth (6.73 ± 0.12 OD 600), and 17350 ± 170 mL/L of hydrogen production from strain G117. The analysis of total-mass and electron balances suggest that this bioprocess is remarkably efficient (82–99%), and records the highest yield of hydrogen (2.27 ± 0.02 mol/mol glycerol) ever reported in literature. [Display omitted] • Clostridium beijerinckii G117 produces hydrogen from <15 g/L of crude glycerol (CG). • While raising CG to 20–80 g/L in the media, strain G117 rejects 34–90% of CG supplied. • Adding agro-residual hydrolysates/metal-ions alter CG-utilization and hydrogen yield. • Media of CG with rice bran hydrolysate as co-substrate and Fe2+ is optimized (OpM). • OpM supports G117 to produce 17350 mL/L hydrogen with yield of 2.27 mol H2 /mol Glycerol. [ABSTRACT FROM AUTHOR]