Pretreatment of Jerusalem artichoke stalk using hydroxylammonium ionic liquids and their influences on 2,3-butanediol fermentation by Bacillus subtilis

Energy Applications of Ionic Liquids: Recent Developments and Future Prospects

Ionic liquids (ILs) consisting entirely of ions exhibit many fascinating and tunable properties, making them promising functional materials for a large number of energy-related applications. For example, ILs have been employed as electrolytes for electrochemical energy storage and conversion, as heat transfer fluids and phase-change materials for thermal energy transfer and storage, as solvents and/or catalysts for CO2 capture, CO2 conversion, biomass treatment and biofuel extraction, and as high-energy propellants for aerospace applications. This paper provides an extensive overview on the various energy applications of ILs and offers some thinking and viewpoints on the current challenges and emerging opportunities in each area. The basic fundamentals (structures and properties) of ILs are first introduced. Then, motivations and successful applications of ILs in the energy field are concisely outlined. Later, a detailed review of recent representative works in each area is provided. For each application, the role of ILs and their associated benefits are elaborated. Research trends and insights into the selection of ILs to achieve improved performance are analyzed as well. Challenges and future opportunities are pointed out before the paper is concluded.

The pretreatment of the sustainable biomass feedstock of Pennisetum giganteum for biorefinery using deep eutectic solvents

In this study, Pennisetum giganteum (PG) was investigated as lignocellulosic feedstock to be pretreated by the acidic and basic deep eutectic solvents (DESs) to generate monomeric sugars. The basic DESs showed excellent efficiency of delignification and saccharification. ChCl/MEA can remove 79.8 % lignin and reserve 89.5 % cellulose. As a result, 95.6 % glucose and 88.0 % xylose yield were obtained, significantly enhanced 9.4 and 15.5 times in contrast with those of the unpretreated PG. The 3D microstructures of raw and pretreated PG were constructed for the first time to better investigate the pretreatment effect on its structure. The increasing porosity (20.5 %) and the reducing CrI (42.2 %) contributed in enhancing enzymatic digestion. Moreover, the recyclability of DES indicated that at least 90 % DES was recovered and 59.5 % lignin still can removed with 79.8 % glucose were obtained after five recycling cycles. Meanwhile, 51.6 % lignin was recovered throughout the recycling process.

One-pot synthesis of fuel precursor from acetoin fermentation broth using ionic liquid-based salting-out extraction system

BACKGROUND

The development of biofuels, especially liquid hydrocarbon fuels, has been widely concerned due to the depletion of fossil resources. In order to obtain fuel precursors, the reaction of C-C bond formation is usually carried out with biomass derived ketones/aldehydes as reactants. Acetoin and 2,3-butanediol are two platform chemicals, which are co-existed in fermentation broth and traditionally separated by distillation, and then acetoin could be use as C4 building block to prepare hydrocarbon fuels. In order to mitigate the process complexity, direct aldol condensation reaction of acetoin in fermentation broth was studied in this work.

RESULTS

A one-pot process of product separation and acetoin derivative synthesis was proposed based on salting-out extraction (SOE). Aldol condensation reaction of acetoin and 5-methyl furfural in different SOE systems was compared, and the results showed that the synthesis of C₁₀ fuel precursors and separation of C₁₀ products and 2,3-butanediol from fermentation broth were achieved in one-pot with ethanolammonium butyrate (EOAB) and K₂HPO₄ as SOE reagents and catalysts. The SOE and reaction conditions such as the concentrations of EOAB and K₂HPO₄, reaction temperature and time were optimized. When the system was composed of 6 wt% EOAB-44 wt% K₂HPO₄ and the mixture was stirred for 6 h at 200 rpm, 40 ℃, the yield of C₁₀ products was 80.7%, and 95.5% 2,3-butanediol was distributed to the top EOAB-rich phase. The exploration of reaction mechanism showed that an imine intermediate was rapidly formed and the subsequent C₁₀ product formation was the key step for aldol condensation reaction.

CONCLUSIONS

With EOAB and K₂HPO₄ as SOE reagents and catalysts, one-pot synthesis of fuel precursor from acetoin fermentation broth was achieved without prior purification. A yield of 80.7% for C₁₀ products was obtained which was accumulated at the interface of two aqueous-phase, and 95.5% 2,3-BD was distributed to the top EOAB-rich phase. This work provides a new integration process of product separation and derivative synthesis from fermentation broth based on ionic liquid SOE.

Ergosterol production at elevated temperatures by Upc2-overexpressing Kluyveromyces marxianus using Jerusalem artichoke tubers as feedstock

Ergosterol is an important precursor in the pharmaceutical industry for the production of numerous drugs. In this study, Kluyveromyces marxianus that showed more potential for ergosterol production than some other yeasts was reported. The effects of transcription factors UPC2, MOT3, and ROX1 of K. marxianus on ergosterol synthesis were explored, and a Upc2-overexpressing strain produced 1.78 times more ergosterol (167.33 mg/L) than the wild-type strain (60.04 mg/L). A total of 239.98 mg/L ergosterol was produced when glucose was replaced with fructose to limit ethanol production. Enhanced aeration increased ergosterol titer from 63.09 mg/L to 128.46 mg/L at 42 °C. The ergosterol titer reached 304.37 mg/L in a shake flask at 37 °C, or 1124.38 and 948.32 mg/L at 37 °C and 42 °C, respectively, in a 5 L bioreactor, using Jerusalem artichoke tubers as the sole carbon source. This study establishes a platform for ergosterol biosynthesis using inexpensive materials.