Kenji Takahashi
Posters-Accepted Abstracts: J Fundam Renewable Energy Appl
Ionic liquids (ILs) have received much attention recently for pretreatment of lignocellulosic biomass, because ILs can dissolve
cellulose and that cellulose re-precipitated after being dissolved in ILs exhibits a much greater efficiency of enzymatic hydrolysis
due to its decreased crystallinity. Moreover, it has been extended this IL-assisted pretreatment method to various lignocellulosic
biomasses and demonstrated that the IL-assisted pretreatment methods are more effective than the conventional methods using
diluted acid or ammonia. In the IL-assisted pretreatment process, the pretreated biomass has to be washed extensively so as to
remove the residual IL because the residual IL in pretreated biomass causes inhibition of cellulolytic enzymes and fermentative
microorganisms during saccharification and fermentation. However, this extensive washing of pretreated biomass results in large
amounts of diluted IL aqueous solution, which leads to a high cost for concentrating IL from its diluted aqueous solution by
evaporation and for treating the resultant wastewater. The cost issue can be an obstacle for scale-up of IL-assisted pretreatment
processes. Recently, we suggested a simple process comprising IL-assisted pretreatment and in situ enzymatic saccharification
without washing out IL from the pretreated biomass and with the addition of a smaller amount of water for diluting IL in order to
save costs derived from the extensive washing step. To reduce the water use for diluting IL and to achieve the higher sugar yield/
concentration in the in situ enzymatic saccharification, the following factors are important: 1) high loading of biomass to IL (less
IL amount per unit biomass) during the IL pretreatment step, reducing water use per unit biomass; 2) use of biocompatible IL
and/or IL-tolerant cellulase enzymes, which reduce water use for diluting IL before enzymatic saccharification because a higher
IL concentration is possible. Some in situ enzymatic saccharification has even been performed by employing biocompatible
IL as well as conventional IL. Our previous study demonstrated that choline acetate (ChOAc) was less toxic for fermentative
microorganisms than imidazolium ionic liquids. We will report on in situ enzymatic saccharification using cholinium IL as a
candidate for biocompatible IL. The data for pretreatment capability, inhibition to commercial cellulase, and performance of the
in situ saccharification process will be then compared with data obtained using the standard imidazolium IL. Moreover, we will
demonstrate an electrodialysis-assisted separation of IL and monomeric sugar obtained by in situ enzymatic saccharification.
This separation technique is very important to use ILs in pretreatment processes.
