Functional insights into inhibition by steam-exploded brewery spent grain hydrolysate in anaerobic digestion: roles of ammonia, volatile fatty acids, and phenolics

production. Despite these stresses, Methanothrix remained the dominant methanogen, suggesting a persistent predominance of acetoclastic methanogenesis, albeit with reduced functional efficiency. Functional predictions for EXP-0.5 suggested a higher representation of pathways related to the citrate cycle, carbohydrate, and amino acid metabolism, implying a potential for sustained energy flux and adaptive responses to ammonia stress. Overall, the results infer that moderate hydrolysate incorporation can attenuate, but not eliminate, inhibition of SE-treated BSG during AD. Therefore, integrated strategies in lignocellulosic biorefinery schemes using SE hydrolysates are required to balance the benefits of enhanced solubilization with microbial metabolic resilience and long-term process stability in AD systems.