Transforming biomass conversion with ionic liquids: process intensification and the development of a high-gravity, one-pot process for the production of cellulosic ethanol

Abstract

Producing concentrated sugars and minimizing water usage are key elements in the economics and environmental sustainability of advanced biofuels. Conventional pretreatment processes that require a water-wash step can result in losses of fermentable sugars and generate large volumes of wastewater or solid waste. To address these problems, we have developed high gravity biomass processing with a one-pot conversion technology that includes ionic liquid pretreatment, enzymatic saccharification, and yeast fermentation for the production of concentrated fermentable sugars and high-titer cellulosic ethanol. The use of dilute bio-derived ionic liquids (a.k.a. bionic liquids) enables one-pot, high-gravity bioethanol production due to their low toxicity to the hydrolytic enzyme mixtures and microbes used. We increased biomass digestibility at >30 wt% by understanding the relationship between ionic liquid and biomass loading, yielding 41.1 g L -1 of ethanol (equivalent to an overall yield of 74.8% on a glucose basis)using an integrated one-pot fed-batch system. Our technoeconomic analysis indicates that the optimized one-pot configuration provides significant economic and environmental benefits for cellulosic biorefineries by reducing the amount of ionic liquid required by ~90% and pretreatment-related water inputs and wastewater generation by ~85%. In turn, these improvements can reduce net electricity use, greenhouse gas-intensive chemical inputs for wastewater treatment, and waste generation. The result is an overall 40% reduction in the cost of cellulosic ethanol produced and a reduction in local burdens on water resources and waste management infrastructure.

Rapid pretreatment of Miscanthus using the low-cost ionic liquid triethylammonium hydrogen sulfate at elevated temperatures

“…Lignocellulose is recalcitrant and requires a pretreatment step in order to release the majority of sugar contained within. 7 Various pretreatment methods are currently under development, such as steam explosion, 8 AFEX, 9 concentrated acid, 10 dilute acid, 11 hot water, 12 organosolv 13,14 and ionic liquid pretreatments, [15][16][17] including ionoSolv fractionation. 18,19 Different strategies are followed, from disrupting the lignocellulosic cell wall structure without separation, [20][21][22][23] to selectively isolating lignin, hemicelluloses and cellulose.…”

“…7 This has opened up new processing options for biomass, including one-pot biofuel production, 2,17 the Ionocell-F spinning of cellulose fibres for fabrics, 38 production of thermally responsive cellulose composites, 39 and production of cellulosic films. 40 Cellulose dissolving ILs have been reported to be amongst the highest-yielding and most feedstock-independent lignocellulose pretreatment technologies, 41 however, the high cost of the required ILs as well as their low thermal stability and their requirement for dry conditions is turning out to be generally prohibitive for biofuel and bulk chemical applications.…”

Demonstrating a separation-free process coupling ionic liquid pretreatment, saccharification, and fermentation withRhodosporidium toruloidesto produce advanced biofuels

“…et al 14 Initial biomass loading was 70 g in the 1 L vessel, 700 g in the 10 L vessel, and 5.25 kg in the 210 L vessel. The pretreatment vessels were loaded with 30% w/w biomass and 70% w/w aqueous fraction, with the aqueous fraction consisting of 90% DI water and 10% cholinium lysinate [ChLys].…”

“…12 Consolidation of pretreatment and saccharification into a one pot process was recently demonstrated with both IL tolerant enzyme cocktails 13 and more recently with bio-derived ILs and commercial enzymes. 14 Further benefits may be obtained by consolidating pretreatment, saccharification and fermentation, eliminating the need to separate ILs from hydrolysates prior to fermentation. These unit operations can be combined either sequentially or in a simultaneous saccharification-fermentation (SSF) process.…”

Overview of the “Ionic Liquids meet Biomolecules” session at the 19th international IUPAB and 11th EBSA congress

“…Seema Singh (Sandia National Laboratories, USA) discusses the role of ILs in enabling the bioeconomy and presents IL applications to facilitate the production of liquid transportation fuels from renewable lignocellulosic biomass. She argues that it is important to perform the pretreatment prior to downstream saccharification and fermentation and also discusses how ILs are overcoming existing barriers and enabling scalable and industrially viable technologies (Socha et al 2014;Xu et al 2016). In her presentation, Seema Singh provides two specific examples of why it is important to understand biomolecule and IL interactions in the context of advancing the one-pot integrated process that will overcome many of the existing barriers in future lignocellulosic biorefineries, including how imidazolium acetate inhibits the activities of cellulase and microbes and how experimental and computational studies are providing insight into designing engineered cellulase, microbes and designer ILs.…”