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

Abstract

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.