Abstract
This study considered the effects of soybean processing methods (raw, roasted, microwaved) and selenium (Se) supplementation (nano-Se, sodium selenite) on in vitro rumen fermentation kinetics and microbial fuel cell (MFC) performance. Soybeans were thermally processed, and gas production (GP) and MFC voltage were measured over 96-120 h. Chemical analysis revealed microwave processing increased crude protein (39.20% vs. 37.35% raw) and reduced fiber content, enhancing digestibility. Gas production kinetics showed microwaved soybeans yielded the highest cumulative GP (312.75 mL/g DM at 96 h), surpassing roasted and raw treatments, likely due to structural modifications improving microbial accessibility. Nano-Se supplementation further amplified GP (320.04 mL/g DM at 96 h) and MFC voltage (3502.60 mV at 120 h), outperforming inorganic Se, attributed to enhanced microbial activity and antioxidant capacity. MFC voltage correlated strongly with GP (r = 0.95-0.99), validating MFCs as a dual-metric tool for assessing fermentation efficiency. Microwave processing generated the highest voltage (3241.30 mV), reflecting efficient electron transfer from disrupted fibrous structures. Nano-Se accelerated microbial kinetics, demonstrating superior bioavailability. Results highlight that thermal processing, particularly microwaving, optimizes nutrient utilization, while nano-Se enhances rumen microbial functions. The integration of GP and MFC metrics provides novel insights into feed degradability and microbial energetics, offering strategies to improve ruminant productivity and reduce environmental impacts. This study underscores the potential of combining advanced processing techniques and selenium supplementation to refine feed formulations and advance sustainable livestock practices.