Rendimento de bio-hidrogênio a partir da fermentação escura do bagaço de malte hidrolisado: pré-tratamentos por explosão a vapor e termo-alcalino

Abstract

The increasing global energy demand, coupled with the environmental impacts of fossil fuel use, has driven the pursuit of alternative and sustainable energy sources. In this context, biohydrogen emerges as a promising option, which can be obtained through various routes, including the biological conversion of agro-industrial residues via dark fermentation. Brewer’s Spent Grain (BSG), the main by-product of the brewing industry, holds considerable potential for energy valorization through this bioprocess, as long as it is subjected to suitable pretreatment methods that enhance its biodegradability. This study aimed to evaluate biohydrogen production via dark fermentation of hydrolyzed BSG subjected to two distinct pretreatment methods: steam explosion and thermo-alkaline processing. Batch experiments were conducted for each pretreatment, testing different substrate/inoculum (S/I) ratios, organic concentrations, steam explosion severities, and the addition of conductive materials. Biohydrogen yields were analyzed alongside volatile fatty acids (VFAs) profiles to assess fermentative dynamics and metabolic selectivity. Results showed that steam explosion led to superior performance, reaching a

maximum yield of 142 mL H2/gCOD, approximately 165% higher than the thermo- alkaline process (54 mL H2/gCOD), due to a stronger predominance of hydrogenogenic

pathways and reduced occurrence of metabolic deviations. Conversely, despite high carbohydrate solubilization and low formation of classical inhibitors, the thermo-alkaline pretreatment was limited by deviant routes and potential redox imbalances induced by the chemical severity of the process. The addition of conductive materials did not significantly improve biohydrogen yields in either scenario, especially under already

optimized conditions (steam explosion) or metabolically unstable environments (thermo- alkaline). Overall, the findings highlight the importance of an integrated optimization between pretreatment strategy and operational conditions to advance biohydrogen production in sustainable biorefinery frameworks.