Dilution strategy to obtain H2 in the 2nd acidogenic phase from enzymatically pre-treated sugarcane bagasse

Sugarcane bagasse (SCB) pre-treated with laccase was used as substrate in two acidogenic phases (1 P and 2 P). In 1 P, the pretreatment conditions were statistically optimized (pH 4.0, 37 °C, 0.4 U of laccase/mL, 24.0 g SCB/L and 120 min of reaction), which allowed obtaining 84% more H₂ (166.8 mL/L) than SCB in natura (90.4 mL/L). In 2 P, the liquid fraction of the 1 P reactors was diluted (90%) and more 108.5 ml H₂/L was obtained. Furthermore, the quantification of enzymes genes responsible for the hydrolysis (Cel) and H₂ production (Hyd) was carried out. An increase in the expression of both genes was observed from the phase of highest H₂ production rates in P1. In 2 P, the 1 P low genic expression was indicative of the autochthonous bacteria activity. The 2nd acidogenic phase strategy proved to be a promising novelty for the use of pre-hydrolyzed substrates with concomitant production of more value-added products.