Efficient Hydrolysis of Lignocellulose by Acidic Ionic Liquids under Low-Toxic Condition to Microorganisms

Kosuke Kuroda,Kazuaki Ninomiya,Kyohei Miyamura,Heri Satria,Kenji Takada,Kenji Takahashi,Ken Inoue

doi:10.3390/catal7040108

Kosuke Kuroda, Kazuaki Ninomiya + Show 5 more

Open Access

https://doi.org/10.3390/catal7040108

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Abstract

Lignocellulose is known as a renewable resource, and acidic ionic liquids have been highlighted as efficient catalysts for hydrolysis of cellulose. To achieve successive hydrolysis and fermentation, efficient hydrolysis with sufficiently diluted acidic ionic liquids is necessary because acidic ionic liquids are toxic to fermentative microorganisms. Escherichia coli was confirmed to grow in 0.05 M dilute acidic ionic liquid—1-(1-butylsulfonic)-3-methylimidazolium hydrogen sulfate ([Sbmim][HSO4])—although the growth was suppressed in more concentrated solutions. Therefore, we applied the 0.05 M [Sbmim][HSO4] solution to hydrolysis of bagasse, leading to a glucose yield of 48% at 190 °C. This value is greater than that obtained with a concentrated [Sbmim][HSO4] solution, which is not suitable for the growth of Escherichia coli (yield: 40% in a 1.0 M solution). Efficient hydrolysis with acidic ionic liquids under low-toxic condition was achieved.

Highlights

Carbohydrates account for 75% of annual renewable biomass
We evaluated the efficacy of hydrolysis by the glucose yield because cellulose is considerably difficult to hydrolyze due to its high crystallinity, as compared with hemicellulose
The 0.05 M [Sbmim][HSO4 ] solution was sufficiently low to allow for the growth of E. coli

Summary

Introduction

Carbohydrates account for 75% of annual renewable biomass. Among the various types of carbohydrates, cellulose is the most attractive because it is inedible and inexpensive; it can be obtained on a large scale from biomass 45% of biomass) [1]. The efficient conversion of cellulose to glucose for the production of ethanol and critical building blocks such as succinic acid and gluconic acid via fermentation has been extensively studied [1,2]. Acidic or enzymatic hydrolysis has been used to obtain glucose from cellulose. Hydrolysis using dilute acid is known to be a simple, cost-effective method; it gives low sugar yields and requires a long reaction time [3].

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