Solvent Production Research Articles

Polymethylaminosiloxane Grafted Transition Metal Catalyst DICAT‐V for Chemoselective Aerobic Oxidation of 5‐HMF into 2,5‐Diformyl Furan

AbstractIn the present study polymethylaminosiloxane (PMAS) grafted transition metal catalysts DICAT−M were explored for the chemoselective oxidation 5‐HMF (5‐hydroxymethyl furfural) into DFF (2,5‐diformyl furan). A series of DICAT−M; DICAT−Fe, DICAT−Co, DICAT−Mn, and DICAT−V were synthesized by grafting Fe, Co, Mn, and V, respectively and tested for the oxidation of 5‐HMF. All the synthesized catalysts selectively oxidize 5‐HMF in presence of air without the addition of any base, activator or co‐catalyst. Of the tested catalysts, the vanadium grafted catalyst (DICAT−V) showed an excellent performance with >88 % yield of DFF and >92 % conversion of 5‐HMF in low boiling organic solvent ACN at 110 °C and 20Kg/cm3. The use of ACN facilitated both solvent recovery and product separation process. The structural and surface morphological properties of DICAT−V were studied by using ATR‐FITR, SEM/EDX, XRF, XRD, and BET surface area analysis. Exploration of PMAS provides an excellent backbone architecture with bidentate amine anchors to hold transition metal and resulted in stable, robust, and recyclable catalysts. The plausible reaction mechanism was proposed for DICAT−V assisted chemoselecive aerobic oxidation. Moreover, DICAT−V showed the consistent performance to obtain >88 % yield and >90 % conversion for five consecutive recycle runs. Thus the employment of DICAT−V for 5‐HMF oxidation contributes to the development of the green and sustainable process by integrating recyclable catalyst, additive‐free protocol, LBP solvent, air as the oxidant, and high process throughputs.

The Small RNA sr8384 Is a Crucial Regulator of Cell Growth in Solventogenic Clostridia.

Small RNAs (sRNAs) are crucial regulatory molecules in organisms and are well-known not only for their roles in the control of diverse crucial biological processes but also for their value in regulation rewiring. However, to date, in Gram-positive anaerobic solventogenic clostridia (a group of important industrial bacteria with exceptional substrate and product diversity), sRNAs remain minimally explored, and thus there is a lack of detailed understanding regarding these important molecules and their use as targets for genetic improvement. Here, we performed large-scale phenotypic screens of a transposon-mediated mutant library of Clostridium acetobutylicum, a typical solventogenic clostridial species, and discovered a novel sRNA (sr8384) that functions as a crucial regulator of cell growth. Comparative transcriptomic data combined with genetic and biochemical analyses revealed that sr8384 acts as a pleiotropic regulator and controls multiple targets that are associated with crucial biological processes through direct or indirect interactions. Notably, the in vivo expression level of sr8384 determined the cell growth rate, thereby affecting the solvent titer and productivity. These findings indicate the importance of the sr8384-mediated regulatory network in C. acetobutylicum Furthermore, a homolog of sr8384 was discovered and proven to be functional in another important Clostridium species, C. beijerinckii, suggesting the potential broad role of this sRNA in clostridia. Our work showcases a previously unknown potent and complex role of sRNAs in clostridia, providing new opportunities for understanding and engineering these anaerobes.IMPORTANCE The uses of sRNAs as new resources for functional studies and strain modifications are promising strategies in microorganisms. However, these crucial regulatory molecules have hardly been explored in industrially important solventogenic clostridia. Here, we identified sr8384 as a novel determinant sRNA controlling the cell growth of solventogenic Clostridium acetobutylicum Based on a detailed functional analysis, we further reveal the pleiotropic function of sr8384 and its multiple direct and indirect crucial targets, which represents a valuable source for understanding and optimizing this anaerobe. Of note, manipulation of this sRNA achieves improved cell growth and solvent synthesis. Our findings provide a new perspective for future studies on regulatory sRNAs in clostridia.

A CRISPR/Anti-CRISPR Genome Editing Approach Underlines the Synergy of Butanol Dehydrogenases in Clostridium acetobutylicum DSM 792.

Although Clostridium acetobutylicum is the model organism for the study of acetone-butanol-ethanol (ABE) fermentation, its characterization has long been impeded by the lack of efficient genome editing tools. In particular, the contribution of alcohol dehydrogenases to solventogenesis in this bacterium has mostly been studied with the generation of single-gene deletion strains. In this study, the three butanol dehydrogenase-encoding genes located on the chromosome of the DSM 792 reference strain were deleted iteratively by using a recently developed CRISPR-Cas9 tool improved by using an anti-CRISPR protein-encoding gene, acrIIA4 Although the literature has previously shown that inactivation of either bdhA, bdhB, or bdhC had only moderate effects on the strain, this study shows that clean deletion of both bdhA and bdhB strongly impaired solvent production and that a triple mutant ΔbdhA ΔbdhB ΔbdhC was even more affected. Complementation experiments confirmed the key role of these enzymes and the capacity of each bdh copy to fully restore efficient ABE fermentation in the triple deletion strain.IMPORTANCE An efficient CRISPR-Cas9 editing tool based on a previous two-plasmid system was developed for Clostridium acetobutylicum and used to investigate the contribution of chromosomal butanol dehydrogenase genes during solventogenesis. Thanks to the control of cas9 expression by inducible promoters and of Cas9-guide RNA (gRNA) complex activity by an anti-CRISPR protein, this genetic tool allows relatively fast, precise, markerless, and iterative modifications in the genome of this bacterium and potentially of other bacterial species. As an example, scarless mutants in which up to three genes coding for alcohol dehydrogenases are inactivated were then constructed and characterized through fermentation assays. The results obtained show that in C. acetobutylicum, other enzymes than the well-known AdhE1 are crucial for the synthesis of alcohol and, more globally, to perform efficient solventogenesis.

Genomic and metabolic insights into solvent production by Thermoanaerobacterium thermosaccharolyticum GSU5

Thermoanaerobacterium thermosaccharolyticum GSU5 was isolated from animal dung collected in a pasture plain in Buenos Aires, Argentina. This thermophilic and anaerobic microorganism was able to produce butanol and ethanol, but not acetone, using sugars such as xylose, arabinose, glucose, galactose, fructose, sucrose, and cellobiose. Key metabolic enzymes leading to solvent production were identified in its genome. A detailed analysis of the solvent and organic acid biosynthetic pathway genes of sequenced strains revealed new insights into the unique metabolic features of this species. Genes required for the synthesis of acetone are absent in the genomes of all sequenced Thermoanaerobacterium, suggesting that it is a general trait of the genus. Strains able to produce butanol synthesize butyrate through the one step pathway catalyzed by the butyryl-CoA:acetate-CoA transferase (But). The large range of fermentable substrates and the ability to produce both ethanol and butanol without acetone makes this species an interesting candidate for second generation biofuel production.

Effects of Spo0A on Clostridium acetobutylicum with an emphasis on biofilm formation

Clostridium acetobutylicum is a well-known strain for biofuel production. In previous work, it was found that this strain formed biofilm readily during fermentation processes. Biofilm formation could protect cells and enhance productivities under environmental stresses in our previous work. To explore the molecular mechanism of biofilm formation, Spo0A of C. acetobutylicum was selected to investigate its influences on biofilm formation and other physiological performances. When spo0A gene was disrupted, the spo0A mutant could hardly form biofilm. The aggregation and adhesion abilities of the spo0A mutant as well as its swarming motility were dramatically reduced compared to those of wild type strain. Sporulation was also negatively influenced by spo0A disruption, and solvent production was almost undetectable in the spo0A mutant fermentation. Furthermore, proteomic differences between wild type strain and the spo0A mutant were consistent with physiological performances. This is the first study confirming a genetic clue to C. acetobutylicum biofilm and will be valuable for biofilm optimization through genetic engineering in the future.

Xylitol solubility in DMF + ethylene glycol or 1,2-propylene glycol: Measurement and modeling with PC-SAFT and CPA equations of state and UNIFAC activity coefficient model

Xylitol is a sugar alcohol that can be produced from biomass. It has applications in the food, pharmaceutical and dental sectors. As a building block of the chemical industry, it can be used in the production of fuels and solvents. The development of productive processes based on this material requires studies related to reactional media and separation systems. Solid-liquid equilibrium experiments associated with the application of mathematical models assist in the search for solutions to these demands. Based on the importance of the subject, a study is presented on xylitol solubility in binary liquid solutions formed by N,N-dimethylformamide, ethylene glycol and 1,2-propylene glycol at different temperatures. The experimental results were treated by two equations of state, PC-SAFT and CPA, and by the UNIFAC activity coefficient model. A dependence of the solubility on temperature and on the composition of the binary liquid solution, was observed. The efficient application of the models generated binary interaction parameters for the equations of state and revealed the predictive capacity of the UNIFAC model.

Preparation of l-α-glyceryl phosphorylcholine by hydrolysis of soy lecithin using phospholipase A1 in a novel solvent-free water in oil system

With various applications in the food, pharmaceutical and cosmetics industries, L-Alpha-glycerylphosphorylcholine (l-α-GPC), is a valuable cholinergic substance whose natural resources is limited. Reported enzymatic pathway seems promising comparing chemical synthesis, while the low solubility of PC in water hinders its scaling-up production and involvement of organic solvent entails potential risks. A novel water-in-soybean oil solvent-free medium was applied in enzymatic preparation of l-α-GPC catalyzed by phospholipase A1, where 99.1% of the PC in soy lecithin was hydrolyzed with l-α-GPC yield of 95.8% (conditions: oil to PC ratio 4:1, water addition 30 wt%, enzyme loading 5 wt%, 55 °C, 3 h). The purity and recovery of purified (silica chromatography) l-α-GPC a with 94.8% and 83.0%, respectively. Efficient and intensive l-α-GPC preparation could be achieved using soybean oil medium, and the proposed system is with advantages of solvent-free, significant reduction of water, offering a green and practical approach for future l-α-GPC production.

RRNPP-type quorum-sensing systems regulate solvent formation, sporulation and cell motility in Clostridium saccharoperbutylacetonicum

BackgroundClostridium saccharoperbutylacetonicum N1-4 (HMT) is a strictly anaerobic, spore-forming Gram-positive bacterium capable of hyper-butanol production through the well-known acetone–butanol–ethanol fermentation process. Recently, five putative RRNPP-type QSSs (here designated as QSS1 to QSS5) were predicted in this bacterial strain, each of which comprises a putative RRNPP-type regulator (QssR1 to QssR5) and a cognate signaling peptide precursor (QssP1 to QssP5). In addition, both proteins are encoded by the same operon. The functions of these multiple RRNPP-type QSSs are unknown.ResultsTo elucidate the function of multiple RRNPP-type QSSs as related to cell metabolism and solvent production in N1-4 (HMT), we constructed qssR-deficient mutants ΔR1, ΔR2, ΔR3 and ΔR5 through gene deletion using CRISPR–Cas9 and N1-4-dcas9-R4 (with the QssR4 expression suppressed using CRISPR–dCas9). We also constructed complementation strains by overexpressing the corresponding regulator gene. Based on systematic characterization, results indicate that QSS1, QSS2, QSS3, and QSS5 positively regulate the sol operon expression and thus solvent production, but they likely negatively regulate cell motility. Consequently, QSS4 might not directly regulate solvent production, but positively affect cell migration. In addition, QSS3 and QSS5 appear to positively regulate sporulation efficiency.ConclusionsOur study provides the first insights into the roles of multiple RRNPP-type QSSs of C. saccharoperbutylacetonicum for the regulation of solvent production, cell motility, and sporulation. Results of this study expand our knowledge of how multiple paralogous QSSs are involved in the regulation of essential bacterial metabolism pathways.

Catalytic conversion of levulinic acid under noncorrosive conditions using Ru/Zr/Al-SBA-15 catalysts

Abstract Herein we report the synthesis of Ru/Zr/Al-SBA-15 catalysts, their characterization by XRD, FT-IR, BET, ICP, FE-SEM, HR-TEM, HAADF-STEM, XPS, TPR, TPD, TGA/DTA and UV-DRS techniques and their catalytic activity towards the hydrogenation of levulinic acid (LA) at ambient H2 pressure under non-corrosive conditions. As the product 2-Methyl Tetrahydrofuran (2-MTHF) obtained in the hydrogenation of levulinic acid is a promising platform chemical having wide applications in the production of biofuels, fine chemicals and green solvents, this research work carries significance. The characterization studies revealed the presence of Zr species well dispersed on SBA-15 and upto 5% loading of Ru over Zr/Al-SBA-15 preserved the mesoporous structure of bare SBA-15. Among the different catalysts, 5% Ru/Zr/Al-SBA-15 (ISM) exhibited the highest catalytic activity with 97% conversion and 84% selectivity towards MTHF in the hydrogenation of levulinic acid without using any solvent. 5% Ru/Zr/Al-SBA-15 catalyst was also synthesized by other methods such as traditional impregnation method (TIM) and ultrasonication method (USM). 5% Ru/Zr/Al-SBA-15 (ISM) showed different morphologies depending on the preparative methods and their catalytic performances were found to be dependent on the method of synthesis. The recyclability of the best catalyst was tested upto five cycles and there was not much variation in terms of conversion and selectivity.

RRNPP-type quorum sensing affects solvent formation and sporulation in Clostridium acetobutylicum.

The strictly anaerobic bacterium Clostridium acetobutylicum is well known for its ability to convert sugars into organic acids and solvents, most notably the potential biofuel butanol. However, the regulation of its fermentation metabolism, in particular the shift from acid to solvent production, remains poorly understood. The aim of this study was to investigate whether cell–cell communication plays a role in controlling the timing of this shift or the extent of solvent formation. Analysis of the available C. acetobutylicum genome sequences revealed the presence of eight putative RRNPP-type quorum-sensing systems, here designated qssA to qssH, each consisting of an RRNPP-type regulator gene followed by a small open reading frame encoding a putative signalling peptide precursor. The identified regulator and signal peptide precursor genes were designated qsrA to qsrH and qspA to qspH, respectively. Triplicate regulator mutants were generated in strain ATCC 824 for each of the eight systems and screened for phenotypic changes. The qsrB mutants showed increased solvent formation during early solventogenesis and hence the QssB system was selected for further characterization. Overexpression of qsrB severely reduced solvent and endospore formation and this effect could be overcome by adding short synthetic peptides to the culture medium representing a specific region of the QspB signalling peptide precursor. In addition, overexpression of qspB increased the production of acetone and butanol and the initial (48 h) titre of heat-resistant endospores. Together, these findings establish a role for QssB quorum sensing in the regulation of early solventogenesis and sporulation in C. acetobutylicum .

Palladium Nanoparticle-Bentonite Hybrid Using Leaves of Syzygium aqueum Plant from India: Design and Assessment in the Catalysis of –C–C– Coupling Reaction

An environment-friendly synthesis process has been developed with the aid of Syzygium aqueum (water apple) leaves extract. Pulverized leaves of Syzygium aqueum (water apple) are mixed with a universal solvent such as water for the preparation of Pd nanoparticle supported on activated Bentonite. The extract from the plant leaves acts both as a reducing agent and also as a capping agent for converting the PdCl2 to PdNPs. The synthesized PdNPs are supported on modified clay and they are characterized by using FTIR, BET, HR-TEM, ICP-MS, TGA, XRD, and FE-SEM/EDX. It is found that the supported PdNPs give high rate of conversions of Suzuki–Miyaura coupling products and give greater than 90% products in universal solvent i.e. water at fairly low temperature. It shows the potential for the environment-friendly synthesis of prime organic molecules like excellent biaryl derivatives with TONs and TOFs with economical and efficient catalyst loading. We recorded high activity, chemoselectivity and excellent TONs (15,061–20,537) and TOFs (100,407–136,919) by using a small catalyst loading in short reaction time only 15 min. The catalyst shows a long lifetime (ten times). Experiments are performed, recycling it, which demonstrate the sustainability and efficiency of the catalytic process. The prepared catalyst gives a higher percentage of coupling product in the lower time. The supported PdNPs help to form good selectivity and efficacy. The catalyst is found highly stable and can be recycled ten times with no appreciable loss in the efficiency. Graphical abstract

Refined study on lithium ion battery combustion in open space and a combustion chamber

More refined combustion tests on 18,650-type lithium ion batteries (LIBs) are conducted both in open space (OS test) and a combustion chamber (CC test). High-speed camera is used to capture the fast rupture and ignition of LIB. In OS tests, jet-flame height increases with the state of charge (SOC), ranging from 0.095 to 0.217m for 70–100% SOC cell. The ejecting velocity of fragments reaches 30m s−1. In CC tests, the electrolyte solvent and flammable gas products are ignited by the ignition rods leading to deflagration and more complete combustion than that in open space. The predicted mass loss ratio of LIB is 14.36% agreeing with experiments. As SOC increases, more lithium metal is available in anode to react with electrolyte to generate more flammable gases. Higher SOC leads to higher specific combustion heat of the mixed gas products, thus increases the severity of thermal runaway and combustion. The total heat release of a LIB fire can be predicted by adding the contribution of all organics’ combustion heats based on thermodynamic data.

Synthesis of Novel Furo[3,2‐c]coumarin Derivatives through Multicomponent [4+1] Cycloaddition Reaction Using ZnO/FAp as a Sustainable Catalyst

AbstractAn efficient green protocol is developed for the synthesis of ten new furo[3,2‐c]coumarin derivatives employing zinc oxide loaded on fluorapatite (ZnO/FAp) as catalyst. The three‐component one‐pot condensation occurs between the 4‐hydroxycoumarin, isocyanide and selected aldehyde in ethanol solvent at room temperature. Excellent yields (94‐98 %) of target products in 16‐20 min reaction time is the attractive feature. As‐synthesized catalysts and organic compounds were fully established by powder‐XRD, TEM, SEM, EDX, FT‐IR, BET, HRMS, 1H NMR and 13C NMR analysis. The catalyst is recyclable up to five times with high efficacy and marginal loss of activity. The reaction facilitated 98 % of the atom economy and 100 % carbon efficiency. Other advantages of the protocol are mild reaction conditions, easy‐workup, green solvent, catalyst reusability, and chromatography free products.

A novel regulatory pathway consisting of a two-component system and an ABC-type transporter contributes to butanol tolerance in Clostridium acetobutylicum.

Despite the long-term interest in solventogenic clostridia-based ABE (acetone-butanol-ethanol) fermentation, clostridial butanol tolerance and its underlying mechanism remain poorly understood, which is a major obstacle hindering further improvements of this important fermentative process. In this study, a two-component system (TCS), BtrK/BtrR, was identified and demonstrated to positively regulate butanol tolerance and ABE solvent formation in Clostridium acetobutylicum, a representative species of solventogenic clostridia. The transcriptomic analysis results showed that BtrK/BtrR has a pleiotropic regulatory function, affecting a large number of crucial genes and metabolic pathways. Of the differentially expressed genes, btrTM, encoding a putative ABC-type transporter (named BtrTM), was shown to be under the direct control of BtrR, the response regulator of the BtrK/BtrR TCS. Furthermore, BtrTM was shown to contribute to more butanol tolerance (46.5% increase) by overexpression, revealing a novel regulatory mechanism consisting of the BtrK/BtrR TCS and the BtrTM transporter in C. acetobutylicum. Based on these findings, we achieved faster growth and solvent production of C. acetobutylicum by overexpressing BtrK/BtrR or its direct target BtrTM, although no significant improvement in the final butanol titer and yield. These results further confirm the importance of BtrK/BtrR and BtrTM in this organism. Also, of significance, a specific number of btrR-btrT-btrM-btrK-like gene clusters were identified in other Clostridium species, including the pathogens Clostridium perfringens and Clostridium botulinum, indicating a broad role for this regulatory module in the class Clostridia.

Contribution to the production and use of biomass-derived solvents – a review

In this review key processes for the synthesis of greener or more sustainable solvents derived from renewable sources (saccharides, lignocellulose and triglycerides) are discussed. It is shown that a series of platform chemicals such as glycerol, levulinic acid and furans can be converted into a variety of solvents through catalytic transformations that include hydrolysis, esterification, reduction and etherification reactions. It was also considered several aspects of each class of solvent regarding performance within the context of the reactions or extractions for which it is employed.

Hydrocracking of Fischer-Tropsch Wax

The low-temperature Fischer-Tropsch synthesis (LTFT) processing of renewable feedstocks combined with the hydrocracking of its solid product is an effective way to produce synthetic renewable engine fuels. The hydrocracking of an FT wax derived from natural gas using the LTFT synthesis was studied in this paper. The hydrocracking was carried out in a tubular fixed-bed reactor with a cocurrent flow of the feedstock and hydrogen. Reaction temperatures in the range of 305– 370 °C, a pressure of 8 MPa, an H2/feed ratio of 500 m3/m3 and weight hour space velocities (WHSV) of 1; 2 and 4 h-1 were tested. The naphtha fraction (boiling up to 200 °C) was the main product of the hydrocracking under all the tested reaction conditions. It could be used as a component into petroleum-derived gasoline in a neat form or the after processing by common refinery processes (isomerization and/or reforming). The production of low-sulfur and low-aromatic paraffinic solvent or the utilization as a feedstock for steam cracking could be some other options of the naphtha fraction utilization. The maximum yield of the gaseous products (depending on the reaction temperatures and WHSV) was 20 wt.%. They were primarily composed of n-alkanes and isoalkanes and could be, therefore, used as an optimal feedstock for steam cracking as well. The C3-C4 fraction of the gaseous products could be also utilized as an LPG fuel. Very low yields (up to 10.4 wt.%) of the middle distillates were obtained under all the tested reaction conditions. Due to their saturated nature, their densities were very low and, additionally, poor low-temperature properties can be expected.

Ferrous-Iron-Activated Transcriptional Factor AdhR Regulates Redox Homeostasis in Clostridium beijerinckii.

The AdhR regulatory protein is an activator of σ54-dependent transcription of adhA1 and adhA2 genes, which are required for alcohol synthesis in Clostridium beijerinckii Here, we identified the signal perceived by AdhR and determined the regulatory mechanism of AdhR activity. By assaying the activity of AdhR in N-terminally truncated forms, a negative control mechanism of AdhR activity was identified in which the central AAA+ domain is subject to repression by the N-terminal GAF and PAS domains. Binding of Fe2+ to the GAF domain was found to relieve intramolecular repression and stimulate the ATPase activity of AdhR, allowing the AdhR to activate transcription. This control mechanism enables AdhR to regulate transcription of adhA1 and adhA2 in response to cellular redox status. The mutants deficient in AdhR or σ54 showed large shifts in intracellular redox state indicated by the NADH/NAD+ ratio under conditions of increased electron availability or oxidative stress. We demonstrated that the Fe2+-activated transcriptional regulator AdhR and σ54 control alcohol synthesis to maintain redox homeostasis in clostridial cells. Expression of N-terminally truncated forms of AdhR resulted in improved solvent production by C. beijerinckiiIMPORTANCE Solventogenic clostridia are anaerobic bacteria that can produce butanol, ethanol, and acetone, which can be used as biofuels or building block chemicals. Here, we show that AdhR, a σ54-dependent transcriptional activator, senses the intracellular redox status and controls alcohol synthesis in Clostridium beijerinckii AdhR provides a new example of a GAF domain coordinating a mononuclear non-heme iron to sense and transduce the redox signal. Our study reveals a previously unrecognized functional role of σ54 in control of cellular redox balance and provides new insights into redox signaling and regulation in clostridia. Our results reveal AdhR as a novel engineering target for improving solvent production by C. beijerinckii and other solventogenic clostridia.

Immobilization of enzymes and cells on lignocellulosic materials

The rising activities of global agriculture and forestry industries are producing huge amounts of lignocellulosic waste, which needs to be well recycled. The management of this waste involves environmental, social, economic and political challenges. Lignocellulosics have been commonly used for construction materials and energy production, thus achieving positive social and environmental impacts. Lignocellulosics represent also a promising feedstock for the production of carriers for enzyme and cell immobilization. Immobilization is a technique in which the biocatalyst is fixed on the surface of an insoluble matrix, allowing to recover the biocatalyst after reaction. The support must have specific characteristics such as inertness, physical strength, stability, renewability and low cost. These characteristics are fulfilled by lignocellulosic materials. Here, we review the applications of lignocellulosic biomass for fermentation, remediation of contaminated water and soil, synthesis of solvents and fine chemicals, juices clarification, and production of fructooligosaccharides. Recycling lignocellulosic waste for the immobilization of enzymes and cells allow to reduce environmental issues. Processes using immobilized cells and enzymes give high rates of solvent productivity, of 1.44–1.67 g/Lh, activity retention, around 90%, and stability, above five cycles of reaction.

Techno-Economic Analysis (TEA) of Different Pretreatment and Product Separation Technologies for Cellulosic Butanol Production from Oil Palm Frond

Among the driving factors for the high production cost of cellulosic butanol lies the pretreatment and product separation sections, which often demand high amounts of energy, chemicals, and water. In this study, techno-economic analysis of several pretreatments and product separation technologies were conducted and compared. Among the pretreatment technologies evaluated, low-moisture anhydrous ammonia (LMAA) pretreatment has shown notable potential with a pretreatment cost of $0.16/L butanol. Other pretreatment technologies evaluated were autohydrolysis, soaking in aqueous ammonia (SAA), and soaking in sodium hydroxide solution (NaOH) with pretreatment costs of $1.98/L, $3.77/L, and $0.61/L, respectively. Evaluation of different product separation technologies for acetone-butanol-ethanol (ABE) fermentation process have shown that in situ stripping has the lowest separation cost, which was $0.21/L. Other product separation technologies tested were dual extraction, adsorption, and membrane pervaporation, with the separation costs of $0.38/L, $2.25/L, and $0.45/L, respectively. The evaluations have shown that production of cellulosic butanol using combined LMAA pretreatment and in situ stripping or with dual extraction recorded among the lowest butanol production cost. However, dual extraction model has a total solvent productivity of approximately 6% higher than those of in situ stripping model.

Highly Efficient Biphasic System for the Synthesis of Alkyl Lactates in the Presence of Acidic Ionic Liquids

Alkyl lactates are produced from lactic acid via esterification, and are used in the production of plastics, paints, solvents and detergents. In the pursuit of an inexpensive, industry-suitable catalyst for this reaction, the application of protic ionic liquids based on nitrogen base and sulphuric acid is proposed. The ionic liquid was synthesised via a simple reaction of triethylamine and a threefold molar excess of sulphuric acid. Water was added to remove the heat of the reaction. Next, the reaction conditions for the model esterification of 2-ethylhexanol with lactic acid without additional solvent were optimised. Exceptionally mild conditions, i.e., a twofold molar excess of alcohol to lactic acid with the addition of an ionic liquid in a catalytic amount (15 mol%) at 60 °C, resulted in high yields of ethyl and 2-ethylhexyl lactates (96–97%). The driving force of this reaction is the production of a biphasic system with immiscible ester during the reaction. This phenomenon makes it possible to overcome the reaction equilibrium. Using an inexpensive ionic liquid, which could be recycled up to five times without diminution in conversion or selectivity, leads to both a greener and a more economically-viable process.