Influence of substrate loadings on the consolidated bioprocessing of rice straw and sugarcane bagasse biomass using Ruminiclostridium thermocellum

The enhanced fermentation effectiveness of Ruminiclostridium thermocellum on pure microcrystalline cellulose is well established. Here, direct microbial solubilization of pretreated rice straw biomass (PT-RSB) and sugarcane bagasse biomass (PT-SCB) to bioethanol by a Ruminiclostridium thermocellum strain ATCC 31924 was investigated. This study directly compared the influence of low (5 g L⁻¹) and high glucan loadings (20 g L⁻¹, 25 g L⁻¹, and 30 g L⁻¹) of these biomasses on the fermentation performance of strain ATCC 31924 under parallel conditions. Both the type of biomass and their initial glucan loadings impacted metabolic end product profiles and biomass conversion efficiency for strain ATCC 31924. After 144 h, biomass solubilization reached in the range of 25.67% to 61.40% for PT-RSB and 24.25% to 53.85% for PT-SCB, depending on loadings. This study establishes the potential of strain ATCC 31924 for the efficient conversion of low-cost renewable biomass to a carbon neutral product, particularly bioethanol.