Continuous hydrogen production from cheese whey in a single-stage lactate-driven dark fermentation reactor
Brenda Aranda-Jaramillo, Octavio García‐Depraect, Óscar Aguilar-Juárez, Mirelli Archundia-Amador, Elizabeth León‐Becerril
Abstract
Background Cheese whey (CW), a lactose-rich byproduct naturally containing lactic acid bacteria (LAB), can be valorized in a biorefinery approach to co-produce biogenic hydrogen and valuable organic acids. Lactate-driven dark fermentation (LD-DF) has emerged as a promising strategy to mitigate hydrogen inhibition typically caused by LAB overgrowth in conventional DF systems. This study evaluated continuous hydrogen production from CW in a single-stage LD-DF reactor. Methods The 63-day experiment was divided into three stages. In Stage I, the reactor was operated at a hydraulic retention time (HRT) of 24 h with raw CW. In Stage II, the HRT was reduced to 18 h. In Stage III, pre-fermented CW (PF-CW), enriched in lactate, was used at the same HRT. Microbial community dynamics were monitored via 16S rRNA gene amplicon sequencing to identify shifts in dominant bacterial populations. Significant findings Hydrogen production fluctuated between peak and valley phases. The hydrogen productivity of 7.8 L H 2 /L-d was reached using lactate-rich CW. Hydrogen production was negatively correlated with lactate and acetate, but positively with butyrate. Lactobacillus and Clostridium were consistently detected; Clostridium appeared more active during hydrogen peaks, while Lactobacillus dominated during valleys. These findings underscore the importance of microbial balance for optimizing hydrogen production in LD-DF systems.