Highest Acetone-butanol-ethanol Research Articles

Application of fed-batch strategy to fully eliminate the negative effect of lignocellulose-derived inhibitors in ABE fermentation

BackgroundInhibitors that are released from lignocellulose biomass during its treatment represent one of the major bottlenecks hindering its massive utilization in the biotechnological production of chemicals. This study demonstrates that negative effect of inhibitors can be mitigated by proper feeding strategy. Both, crude undetoxified lignocellulose hydrolysate and complex medium supplemented with corresponding inhibitors were tested in acetone–butanol–ethanol (ABE) fermentation using Clostridium beijerinckii NRRL B-598 as the producer strain.ResultsFirst, it was found that the sensitivity of C. beijerinckii to inhibitors varied with different growth stages, being the most significant during the early acidogenic phase and less pronounced during late acidogenesis and early solventogenesis. Thus, a fed-batch regime with three feeding schemes was tested for toxic hydrolysate (no growth in batch mode was observed). The best results were obtained when the feeding of an otherwise toxic hydrolysate was initiated close to the metabolic switch, resulting in stable and high ABE production. Complete utilization of glucose, and up to 88% of xylose, were obtained. The most abundant inhibitors present in the alkaline wheat straw hydrolysate were ferulic and coumaric acids; both phenolic acids were efficiently detoxified by the intrinsic metabolic activity of clostridia during the early stages of cultivation as well as during the feeding period, thus preventing their accumulation. Finally, the best feeding strategy was verified using a TYA culture medium supplemented with both inhibitors, resulting in 500% increase in butanol titer over control batch cultivation in which inhibitors were added prior to inoculation.ConclusionProperly timed sequential feeding effectively prevented acid-crash and enabled utilization of otherwise toxic substrate. This study unequivocally demonstrates that an appropriate biotechnological process control strategy can fully eliminate the negative effects of lignocellulose-derived inhibitors.Graphical

Study on combustion and emissions characteristics of acetone-butanol-Ethanol(ABE)/gasoline premixed fuel in CISI engines

ABE (acetone-butanol-ethanol) was a clean biomass substitute fuel. This paper investigated the combustion and emission performance of ABE/gasoline premixed fuel Combined Injection Spark Ignition engine with various ABE ratios and direct injection ratios. Thus exploring the potential of ABE/gasoline premixed fuel for use in combined injection engines. Results showed that high ABE ratios (≥75 %) can increase maximum cylinder pressure and BMEP by 3.8 % at least with various direct injection ratios (except P0G100), and increasing the duration of the flame development by 28.7 % at least. With different ABE ratios, the duration of the flame propagation increased by 17.1 % at least and maximum heat release rate decreased by 15.8 % at least as the direct injection ratio increased from 0 % to 100 %. With various ABE ratios, using high direct injection ratios (≥75 %) would increase HC emissions by 1.3 % at least, decrease CO emissions by 3.8 % at least and decrease NOx emissions by 11.0 % at least compared to P100G0. Particle Numbers increased with increasing direct injection ratios under different ABE ratios, and reached the minimum value at ABE100 with certain direct injection ratios (≥25 %). Moreover, increasing the ABE blended ratio reduced the number of particles obtained from fuel combustion emissions (except P75G25).

Selective preparation of jet fuels from low carbon alcohols and ABE at atmospheric pressure

Developing efficient jet-fuel synthesis route using bio-based low carbon alcohols or ABE (acetone/butanol/ethanol) is of great significance in reducing carbon emission. The objective of this work is to demonstrate that jet fuels can be selectively prepared from ABE and low carbon alcohols under atmospheric pressure condition. This controllable synthetic strategy was based on the two-step processes: selective dehydration of ABE (or low-carbon alcohols) into light olefins over the Ce@Fe@SAPO-34 catalyst and olefin polymerization into jet fuels over the ionic liquid catalyst ([bmim]Cl–2AlCl3). The optimizations of the catalysts and reaction conditions were investigated in detail. Under the atmospheric pressure, high ABE conversion (89.3%) and high jet fuel yield (71.5%) were achieved through coupling the two-step process.

Acetone–Butanol–Ethanol Catalytic Upgrading into Aromatics over Ga-Modified HZSM-5 Zeolites

The selective conversion of the acetone–butanol–ethanol (ABE) mixture derived from biomass to high-valuable chemicals has attracted intensive attention, while controlling the product selectivity at high ABE conversions is still a challenge. Herein, a bifunctional Ga/HZSM-5 zeolite containing both Brønsted acid sites and Lewis acid sites was designed and utilized as a robust catalyst for the conversion of the ABE mixture to aromatics with a state-of-the-art aromatics yield of 77%. The reaction mechanisms including the aromatics formation and catalyst deactivation were investigated through the catalytic modulation experiments with monocomponents and bicomponents of the ABE mixture and several complementary spectroscopic approaches. A synergistic catalysis between the Lewis acidic Ga species and Brønsted acid sites was proposed, and the structure–activity relationship was established. These results provide some fundamental guidelines to rationally design highly efficient catalysts for the selective catalytic conversion of ABE fermentation.

Butanol–isopropanol fermentation with oxygen-tolerant Clostridium beijerinckii XH29

Acetone–butanol–ethanol (ABE) fermentation is a traditional way for solvents production through bioconversion by Clostridium species. It is still a challenge to obtain metabolic engineering strains with high ABE yield. Screening strains with remarkable characteristics from nature and improving ABE yield by mutation are viable approaches. Clostridium beijerinckii XH 0906, a newly isolated strain, produces butanol and isopropanol (BI) as the main end-products (9.1 g/L BI) during fermentation with glucose as the sole carbon source. The screening process for this strain was performed under aerobic conditions rather than anaerobic environment. Thus, it is a robust stain capable of oxygen-tolerant BI fermentation. Furthermore, C. beijerinckii XH 0906 fermented xylose and glucose simultaneously to produce BI. A mutant strain obtained by ultraviolet (UV) mutagenesis, C. beijerinckii XH 29, had improved BI production capacity and could produce 17.0 g/L BI and 18.4 g/L BI using glucose or corn stover hydrolysate, respectively as the carbon source. Interestingly, C. beijerinckii XH 29 also produced up to 19.3 g/L isopropanol through fermentation of a glucose–acetone mix. These results indicate that C. beijerinckii XH 29 is an excellent BI producer with great potential for industrial applications.Graphical

Biobutanol production from pruned vine shoots

This research aimed to demonstrate the feasibility of producing biobutanol by acetone-butanol-ethanol (ABE) fermentation on vine shoots at laboratory scale. In order to avoid a detoxification process prior to fermentation, an alkaline pretreatment and its posterior enzymatic hydrolysis were optimized through a response surface methodology (RSM) approach to minimize the concentration of phenolic inhibitors and maximize the amount of fermentable sugars. This vine shoots hydrolysate was directly fermented by 11 solventogenic Clostridium strains, reaching butanol concentrations over 8.0 g/L with C. beijerinckii CECT 508 and DSM 6423. The strain CECT 508 was selected to tune up a fermentation medium with the minimum possible amount of nutrients through a Plackett-Burman experimental design, thus reducing the cost of the fermentation broth while ensuring a high ABE solvent production. Finally, it was also shown that CaCO3 could be substituted by eggshell powder as buffering agent, maintaining a biobutanol production over 7 g/L. This study demonstrates, for the first time, that biobutanol production from vine shoots is possible and that cost reduction based on alternative strategies of nutrient supplementation is viable.

Research on the combustion and emissions of an SI engine with acetone-butanol-ethanol (ABE) port injection plus gasoline direct injection

Recently, more attention has been paid to the application of biobutanol in spark ignition (SI) engines due to its superior properties among the biofuels. However, the high energy consumption and low efficiency of recovering biobutanol from ABE solution during the fermentation process lead to the high price of biobutanol, which limits its popularization in vehicles. Using ABE directly can solve the problem of high price of bio-butanol. This research explored the performance of an SI engine with ABE port injection (ABEPI) plus gasoline direct injection (GDI) at different excess air ratio (λ = 0.9, 1.0, 1.1, 1.2) and ABE port injection ratio (ABEPIr = 0, 25%, 50%, 75%, 100%). The results show that CA10-90 declines with increasing ABEPIr. CA0-10 and CA0-90 decrease with ABEPIr increasing at λ = 0.9, and first descend and then rise at λ = 1.0, 1.1 and 1.2. The coefficient of variations of IMEP (CoVIMEP) reaches the minimum value at ABEPIr = 75%. As ABEPIr increases, the peak in-cylinder pressure (Pmax), indicated mean effective pressure (IMEP) and brake thermal efficiency (BTE) increase at λ = 0.9 while first increase and then decrease at λ = 1.0, 1.1 and 1.2, reaching the maximum values at ABEPIr = 75%. Hydrocarbon (HC) reaches the minimum value at ABEPIr = 50%. Particle number decreases dramatically as ABEPIr increases from 0% to 50% and remains at an extremely low level when ABEPIr is greater than 50%. In summary, ABE is suitable for SI engine as an alternative fuel and fuels with high ABE ratio (≥50%) can effectively improve the combustion and particle emissions by ABEPI + GDI combined injection.

Enhancement of acetone-butanol-ethanol fermentation from eucalyptus hydrolysate with optimized nutrient supplementation through statistical experimental designs

Eucalyptus has been previously suggested as a potential substrate for acetone-butanol-ethanol (ABE) production without nutrient supplementation; however, incomplete sugar consumption has prevented improvement of ABE production. Cellulase loading with 35 FPU g−1 was first optimized in terms of high hydrolysis efficiency (95%). However, only 0.43 g L−1 ABE production and 3.44% glucose consumption rate were achieved. To improve ABE production from eucalyptus hydrolysate, supplementation of 6 nutrients in common tryptone-yeast extract (TY) medium were investigated by statistical approaches. Three nutrients including yeast extract, tryptone, and FeSO4·7H2O were screened as significant nutrients for ABE production. Subsequently, use of a modified TY medium (MTY medium: yeast extract 3.04 g L−1, tryptone 7.64 g L−1, FeSO4·7H2O 15.3 mg L−1), which was subsequently predicted by Plackett-Burman and Box-Behnken designs to stimulate ABE production, resulted in ca. 40-fold increase in ABE concentration (16.9 g L−1) and a glucose consumption rate of 100%. We first examined previously uninvestigated nutrition combinations using Plackett-Burman and Box-Behnken designs for high ABE production from eucalyptus hydrolysate. This study shows that statistical method would be a powerful tool for the optimization and enhancement of ABE production from eucalyptus hydrolysate.

Improvement of acetone–butanol–ethanol (ABE) production from switchgrass pretreated with a radio frequency-assisted heating process

Radio frequency (RF) heating assisted alkaline pretreatment was evaluated as an emerging technology to generate hydrolysates for acetone–butanol–ethanol (ABE) fermentation. Traditional water bath (WB) heating was utilized as a control. ABE fermentation was conducted with Clostridium beijerinckii 8052 using the hydrolysates as carbon sources with or without yeast extract (YE, as supplemented complex nitrogen sources). Results indicated that the hydrolysates generated through RF pretreatment (RFH) performed consistently better for ABE fermentation than the hydrolysates generated through WB (WBH), with or without yeast extract (YE) supplementation. Without YE addition, fermentation with RFH generated 50% higher ABE than that with WBH. YE supplementation (up to 5g/L) enhanced fermentation under all conditions and diminished the difference among performances of fermentations. ABE production with 1 and 2g/L YE supplementation increased by 15% and 107% than those without YE for WBH, while for RFH the increase were 1% and 55%, respectively. Supplementation of 5g/L YE brought the final solvent production to be very close to each other with either WBH or RFH. Therefore, we concluded that RFH contained more nutrients than WBH which made a big difference for the ABE fermentation. RF could be explored as an efficient method for biomass pretreatment. This study provided valuable references for developing a sustainable system to convert lignocellulosic biomass into bioenergy in an economically efficient manner.

Periodic peristalsis increasing acetone–butanol–ethanol productivity during simultaneous saccharification and fermentation of steam-exploded corn straw

The acetone-butanol-ethanol (ABE) fermentation of lignocellulose at high solids content has recently attracted extensive attention. However, the productivity of high solids ABE fermentation of lignocellulose is typically low in traditional processes due to the lack of efficient intensifying methods. In the present study, periodic peristalsis, a novel intensifying method, was applied to improve ABE production by the simultaneous saccharification and fermentation (SSF) of steam-exploded corn straw using Clostridium acetobutylicum ATCC824. The ABE concentration and the ABE productivity of SSF at a solids content of 17.5% (w/w) with periodic peristalsis were 17.1g/L and 0.20g/(Lh), respectively, which were higher than those obtained under static conditions (15.2g/L and 0.14g/(Lh)). The initial sugar conversion rate over the first 12h with periodic peristalsis was 4.67g/(Lh) at 10 FPU/g cellulase dosage and 15% (w/w) solids content, an increase of 49.7% compared with the static conditions. With periodic peristalsis, the period of batch fermentation was shortened from 108h to 84h. The optimal operating regime was a low frequency (6h-1) of periodic peristalsis in the acid-production phase (0-48h) of SSF. Therefore, periodic peristalsis should be an effective intensifying method to increase the productivity of ABE fermentation at high solids content.

High acetone–butanol–ethanol production in pH-stat co-feeding of acetate and glucose

We previously reported the metabolic analysis of butanol and acetone production from exogenous acetate by (13)C tracer experiments (Gao etal., RSC Adv., 5, 8486-8495, 2015). To clarify the influence of acetate on acetone-butanol-ethanol (ABE) production, we first performed an enzyme assay in Clostridium saccharoperbutylacetonicum N1-4. Acetate addition was found to drastically increase the activities of key enzymes involved in the acetate uptake (phosphate acetyltransferase and CoA transferase), acetone formation (acetoacetate decarboxylase), and butanol formation (butanol dehydrogenase) pathways. Subsequently, supplementation of acetate during acidogenesis and early solventogenesis resulted in a significant increase in ABE production. To establish an efficient ABE production system using acetate as a co-substrate, several shot strategies were investigated in batch culture. Batch cultures with two substrate shots without pH control produced 14.20g/L butanol and 23.27g/L ABE with a maximum specific butanol production rate of 0.26g/(gh). Furthermore, pH-controlled (at pH 5.5) batch cultures with two substrate shots resulted in not only improved acetate consumption but also a further increase in ABE production. Finally, we obtained 15.13g/L butanol and 24.37g/L ABE at the high specific butanol production rate of 0.34g/(gh) using pH-stat co-feeding method. Thus, in this study, we established a high ABE production system using glucose and acetate as co-substrates in a pH-stat co-feeding system with C.saccharoperbutylacetonicum N1-4.

Performance of fed-batch acetone–butanol–ethanol (ABE) fermentation coupled with the integrated in situ extraction-gas stripping process and the fractional condensation

In this study, fed-batch acetone–butanol–ethanol (ABE) fermentation was coupled with the integrated in situ extraction-gas stripping process. The total glucose consumptions were 255 and 310 g/L at the gas flow rates of 0.5 and 1.0 liter per minute (lpm), respectively. The ABE productivity and yield were 0.65 g/L/h and 0.43 g-solvent/g-glucose at the gas flow rates of 0.5 lpm. When the gas flow rates increased from 0.5 to 1.0 lpm, the ABE productivity and yield became 0.69 g/L/h and 0.48 g-solvent/g-glucose, respectively. The fractional condensation was operated by using two different cold traps where temperatures for the first and second one were 2 and −196°C, respectively. It was found that 71–81 and 64–73% of total stripped water was condensed in the 2 °C cold trap at gas flow rates of 0.5 and 1.0 lpm, respectively. Therefore, high ABE concentrations of 360–460 g/L were found in the second cold trap. The overall separation factor for butanol was calculated to be up to 34 where the raffinate solution is the fermentation broth and the extract solution is the condensate in the −196 °C cold trap.

Feasibility of acetone–butanol–ethanol fermentation from eucalyptus hydrolysate without nutrients supplementation

The economic feasibility of acetone–butanol–ethanol (ABE) fermentation is greatly affected by the type of raw material used. The easy availability of eucalyptus from marginal environments is an alternative feedstock for use as raw material to reduce the production cost. In this study, hydrolyzed eucalyptus was used for ABE production without any nutrients supplementation. Increasing the solid concentration in the eucalyptus slurry from 6.7% (w-dry matter/v) to 25% led to an increase in the initial glucose concentration from 33.7g/L to 86.7g/L after enzymatic hydrolysis. Dosed cellulases not only hydrolyzed cellulose but also supplied nitrogen source for ABE producing strain. However, ABE production from the obtained hydrolysate decreased when the solid concentration was increased to more than 10%. The maximum ABE of 12.3g/L was obtained at 10% solid concentration, with an initial glucose concentration of approximately 40g/L. In addition, the fermentation capability of eucalyptus hydrolysate was found to be improved by diluting the hydrolysate, which prevented inhibition by substrate and fermentation inhibitors. Finally, ABE concentration was improved to 13.1g/L by diluting the hydrolysate from the initial solid concentration of 25% to an initial glucose concentration of 45g/L, which resulted in ABE productivity of 0.109g/L/h and ABE yield of 0.413g/g. Thus, the high ABE production from eucalyptus makes it a potential feedstock for biofuel production.

Continuous Acetone–Butanol–Ethanol (ABE) Fermentation with in Situ Solvent Recovery by Silicalite-1 Filled PDMS/PAN Composite Membrane

The pervaporation (PV) performance of a thin-film silicalite-1 filled PDMS/PAN composite membrane was investigated in the continuous acetone–butanol–ethanol (ABE) production by a fermentation–PV coupled process. Results showed that continuous removal of ABE from the broth at three different dilution rates greatly increased both the solvent productivity and the glucose utilization rate, in comparison to the control batch fermentation. The high solvent productivity reduced the acid accumulation in the broths because most acids were reassimilated by cells for ABE production. Therefore, a higher total solvent yield of 0.37 g/g was obtained in the fermentation–PV coupled process, with a highly concentrated condensate containing 89.11–160.00 g/L ABE. During 268 h of the fermentation–PV coupled process, the PV membrane showed a high ABE separation factor of more than 30 and a total flux of 486–710 g/m2h. Membrane fouling was negligible for the three different dilution rates. The solution-diffusion model, especially the mass transfer equation, was proved to be applicable to this coupled process.

Production of Acetone, Butanol and Ethanol as Bioenergy Source Materials by Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) using Different Substrates

In the effort of developing bioenergy source materials, a laboratorium study was performed to investigate the effects of substrate types and concentrations on the production of acetone-butanol-ethanol (ABE) from various substrates by Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) in defined TYA (Tryptone-Yeast extract-Acetate) media. The results demonstrated that the ABE ratios produced by the strain N1-4 were greatly influenced by the types of substrate and the concentrations being used. It was also shown that fermentation of disaccharides (cellobiose and dextrin) by the strain N1-4 could give relatively as high butanol and ABE yields as glucose fermentation after 24 h fermentation time. The strain N1-4 was also found to be able to ferment xylans from birchwood sources producing a relatively high ABE concentration, especially at a prolonged incubation time (after 48 h incubation period). A subsequent experiment using several different concentrations of glucose or cellobiose revealed that the higher the concentration of the substrate being used, then the higher the total ABE concentration or productivity could be obtained but not necessarily in the same increasing ratio. To the best of our knowledge, there was no other previous study about the effect of substrate type and concentration on the ABE ratio by C. saccharoperbutylacetonicum N1-4 (ATCC 13564) using various substrates in defined TYA media, specifically by using xylans and dextrin substrates.

Acetone–butanol–ethanol production with high productivity using Clostridium acetobutylicum BKM19

Conventional acetone-butanol-ethanol (ABE) fermentation is severely limited by low solvent titer and productivities. Thus, this study aims at developing an improved Clostridium acetobutylicum strain possessing enhanced ABE production capability followed by process optimization for high ABE productivity. Random mutagenesis of C. acetobutylicum PJC4BK was performed by screening cells on fluoroacetate plates to isolate a mutant strain, BKM19, which exhibited the total solvent production capability 30.5% higher than the parent strain. The BKM19 produced 32.5 g L(-1) of ABE (17.6 g L(-1) butanol, 10.5 g L(-1) ethanol, and 4.4 g L(-1) acetone) from 85.2 g L(-1) glucose in batch fermentation. A high cell density continuous ABE fermentation of the BKM19 in membrane cell-recycle bioreactor was studied and optimized for improved solvent volumetric productivity. Different dilution rates were examined to find the optimal condition giving highest butanol and ABE productivities. The maximum butanol and ABE productivities of 9.6 and 20.0 g L(-1) h(-1) , respectively, could be achieved at the dilution rate of 0.85 h(-1) . Further cell recycling experiments were carried out with controlled cell-bleeding at two different bleeding rates. The maximum solvent productivities were obtained when the fermenter was operated at a dilution rate of 0.86 h(-1) with the bleeding rate of 0.04 h(-1) . Under the optimal operational condition, butanol and ABE could be produced with the volumetric productivities of 10.7 and 21.1 g L(-1) h(-1) , and the yields of 0.17 and 0.34 g g(-1) , respectively. The obtained butanol and ABE volumetric productivities are the highest reported productivities obtained from all known-processes.

Enhancement of butanol production and reducing power using a two-stage controlled-pH strategy in batch culture of Clostridium acetobutylicum XY16

The effects of pH control on the process of acetone/butanol/ethanol (ABE) production in batch cultures of Clostridium acetobutylicum XY16 have been investigated. Based on the specific acid- and solvent-forming rates in batch fermentation at different pH values (from 4.3 to 6.0), a two-stage controlled-pH strategy was developed in which the pH was shifted from 5.5 to 4.9 after a dry cell weight of 0.5 g L(-1) was achieved. By applying this strategy, the maximum ABE concentration and productivity reached 20.3 g L(-1) and 0.63 g L(-1) h (-1), and were significantly improved by 12.2 and 40.1 %, respectively, compared with the process with no pH control. In addition, reducing power capability was significantly enhanced by this strategy. The two-stage controlled-pH strategy was a convenient and rapid method for high intensity ABE production.

Fermentation of sago starch to biobutanol in a batch culture using Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564)

Acetone–butanol–ethanol (ABE) was produced in Clostridium saccharoperbutylacetonicum N1-4 using sago starch as a substrate, and the effects of nutrient supplementation on ABE production were studied. Using sago starch as a substrate led to higher butanol production in C. saccharoperbutylacetonicum N1-4 when compared to other starchy materials as substrates. TYA medium supplemented with sago starch led to enhanced ABE and butanol production; however, P2 medium improved ABE production more than TYA medium. The highest ABE and butanol production was achieved with P2 medium supplemented with 70 g/L of sago starch. Using these fermentation conditions, ABE and butanol were produced at 16.65 and 9.83 g/L, respectively, and productivity was 0.15 g/L h for ABE and 0.09 g/L h for butanol. Using P2 medium supplemented with either 50 g/L enzymatically hydrolyzed sago starch or 70 g/L sago starch without hydrolysis, 9.81 and 9.83 g/L butanol were produced, respectively. These results reveal the importance of media formulation in the biobutanol fermentation of sago starch by C. saccharoperbutylacetonicum N1-4.