Co-fermentation of liquid and solid sugarcane byproducts in thermophilic anaerobic compartmented fixed-bed reactors: Unraveling performance and microbial community aspects

Two thermophilic (55 °C) Anaerobic Compartmented Fixed-Bed Reactors (ACFBR; R1 and R2) were operated for 198 days using sugarcane vinasse and bagasse hydrolysate. Hydrothermally pretreated bagasse (200 °C, 16 bar, 10 min) filled 13 modular sections per reactor, serving as both substrate and support. Glass beads (5 mm) were placed between bagasse compartments only in R1. Biohydrogen evolved up to 356 ± 341 and 628 ± 348 NmL H 2 L −1 d −1 in R1 and R2, respectively, even at OLR<18 kg COD m −3 d −1 . Hemicellulose degradation by Caldanaerobius supplied additional substrate for fermentative bacteria. Butyric ( Thermoanaerobacterium , Caproiciproducens ) and valeric ( Clostridium ) acids dominated through chain elongation. Although bagasse alone supported biomass growth, glass beads enhanced biomass retention and acidogenic stability, improving hemicellulose conversion while slightly restricting H 2 transfer. The ACFBR configuration demonstrates potential for integrating sugarcane byproducts into biohydrogen and carboxylate production, with higher OLR and mixed substrates offering routes for process intensification.