Lignocellulose degradation, enzymatic saccharification and bioethanol production from whole-crop sweet sorghum silage inoculated with feruloyl-esterase producing lactic acid bacteria

Commercialization of cellulosic biofuels faces challenges like year-round feedstock availability and lignocellulose recalcitrance. This study ensiled whole-crop sweet sorghum biomass, inoculating it with feruloyl-esterase producing Lactiplantibacillus plantarum A1 to ensure consistent feedstock supply and promote lignin degradation during fermentation. The ensiled biomass underwent 72 h enzymatic saccharification followed by 96 h Saccharomyces cerevisiae fermentation for bioethanol production. Compared to uninoculated controls, L. plantarum A1 inoculation significantly reduced dry matter loss, improved aerobic stability, had higher lactic acid bacteria (LAB) counts, and reduced yeast counts. Inoculation also improved fermentation quality, evidenced by lower pH (3.50 vs 3.66) and higher lactic acid concentrations (44.48 vs 23.56 g/kg DM). Proteolysis was notably reduced, indicated by decreased non-protein nitrogen fractions (P < 0.05). Inoculation enhanced lignin degradation, as shown by lower lignin content, higher ferulic acid concentrations, and disintegrated biomass structure observed via scanning electron microscopy (SEM). These improvements led to increased fermentable sugar availability post-saccharification, resulting in higher ethanol yields during S. cerevisiae fermentation. This study highlights the potential of silage inoculation with feruloyl-esterase producing L. plantarum A1 in optimizing bioethanol production from whole-crop sweet sorghum biomass at a relatively lower cost of pretreatment.