Temporal dynamics and metabolic correlation between lactate-producing and hydrogen-producing bacteria in sugarcane vinasse dark fermentation: The key role of lactate

This study aimed to better understand the role of different microbial groups and the determining fermentation pathways in a biohydrogen (bioH2)-producing reactor fed with sugarcane vinasse by using next-generation sequencing and principal component analysis (PCA). Both microbial structure and dynamics were characterized. The highest bioH2 production levels were associated with the Thermoanaerobacterium genus, whilst lactate-producing bacteria comprised the dominant genera (e.g. Lactobacillus and Leuconostoc) within the reactor at both stable and unstable bioH2-producing periods. PCA further revealed that the fermentation of lactate played a dual role in the reactor, as both bioH2-producing (acetate + lactate → butyrate + bioH2) and non-bioH2-producing (lactate → propionate + acetate) routes could be observed. Overall, the results suggested that lactate is the primary alternative carbon source in vinasse-fed systems subjected to carbohydrate-shortage conditions.