Available online 5 September 2022, 110119

High concentrations of volatile acids were produced in the acidogenic stage.

90% of total volatile fatty acids were converted in the metanogenic stage.

Sugarcane bagasse autochthonous bacteria were favored in the fermentation stage.

Methanoculleus and Methanosaeta were identified in the methanogenic stage.

Potential genes related to hydrolytic enzymes were infered in both stages.

Enzymatically pre-treated sugarcane bagasse (SCB) was used as substrate for sequential production of hydrogen (H2) and methane (CH4). In stage I, SCB was used by autochthonous bacteria, such as Enterococcus (42.4% relative abundance) and Paraclostridium (16.8%) for H2 production (166.8 mL H2/L), while the metabolites accumulated at the end of this stage (9140.5 mg HAc/L) were used by allochthonous inoculum for CH4 production (870.8 mL CH4/L) in stage II. In stage II, hydrogenotrophic (Methanoculleus, 49.1%) and acetoclastic (Methanosaeta, 15.5%) archaeal genera were identified and considered important to maintain low H2 pressure in the system. According to gene inference, the hydrolysis of the SCB fiber was performed in both stages, as potential β-glucosidase and 1,4-β-xylosidase encoding genes were predicted. However, the energy metabolism of microbial populations differed, as potential genes involved in CH4 metabolism were predominant in phase II (39.0%).

Acidogenesis

Methanogenesis

Paraclostridium

Methanoculleus

Methanosaeta

© 2022 Elsevier Inc. All rights reserved.