Stable cellulolytic activity of Clostridium thermocellum against cellulosic biomass pretreated with ionic liquid 1-ethyl 3-methylimidazolium acetate

Using cellulosic biomass has considerable potential for the production of valuable chemicals while contributing to carbon neutrality. This study investigates the effect of biomass pretreatment with ionic liquid 1-ethyl 3-methylimidazolium acetate ([EMIM][Ac]) on the efficiency of enzymatic saccharification using the cellulolytic system of the thermophilic bacterium Clostridium thermocellum. Although [EMIM][Ac] pretreatment improves the efficiency of enzymatic saccharification, it also inhibits the cellulolytic enzyme. Following incubation with 30 % [EMIM][Ac], while the cellulolytic activity of the commercial cellulase cocktail (Celluclast) decreased to 15 % and that of C. thermocellum exoproteome remained stable, suggesting a relative tolerance of C. thermocellum cellulases to [EMIM][Ac]. The reducing sugars released from the pretreated cellulosic biomass corn hull by Celluclast were reduced by 24 % with supplementation of 5 % [EMIM][Ac] but remained unchanged for C. thermocellum exoproteome. These results highlight the potential of [EMIM][Ac] pretreatment of cellulosic biomass as a promising approach for enzymatic saccharification using C. thermocellum.