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Butanol has recently gained increasing interest due to escalating prices in petroleum fuels and concerns on the energy crisis. However, the butanol production cost with conventional acetone–butanol–ethanol fermentation by Clostridium spp. was higher than that of petrochemical processes due to the low butanol titer, yield, and productivity in bioprocesses. In particular, a low butanol titer usually leads to an extremely high recovery cost. Conventional biobutanol recovery by distillation is an energy-intensive process, which has largely restricted the economic production of biobutanol. This article thus reviews the latest studies on butanol recovery techniques including gas stripping, liquid–liquid extraction, adsorption, and membrane-based techniques, which can be used for in situ recovery of inhibitory products to enhance butanol production. The productivity of the fermentation system is improved efficiently using the in situ recovery technology; however, the recovered butanol titer remains low due to the limitations from each one of these recovery technologies, especially when the feed butanol concentration is lower than 1 % (w/v). Therefore, several innovative multi-stage hybrid processes have been proposed and are discussed in this review. These hybrid processes including two-stage gas stripping and multi-stage pervaporation have high butanol selectivity, considerably higher energy and production efficiency, and should outperform the conventional processes using single separation step or method. The development of these new integrated processes will give a momentum for the sustainable production of industrial biobutanol.

Under high ambient pressure (5 MPa) and different injection pressures (90, 120, and 150 MPa), a high‐speed imaging technique was carried out to comparatively investigate the macroscopic spray characteristics of diesel with three different types of blended fuel in a constant volume chamber. The oxygenated fuels were n‐butanol (B), pine oil (P), and 2,5‐dimethylfuran (DMF). All their blending ratio with diesel were 20%. Results showed that less viscosity could be improved the spray characteristics of the fuel in the range of experimental conditions. Then, the tested fuels had a longer penetration and a greater spray area with increasing the injection pressure from 90 to 150 MPa. On the other hand, the percentage increases in the mean spray cone angle of D100, B20, P20, and DMF20 were 3%, 4.4%, 2.4%, and 2.9%, respectively. At the same experimental condition, the spray penetrations of DMF20 and P20 were larger than that of D100, but the spray penetration of B20 was basically similar to D100. Besides, the performance of the spray cone angle and spray area were D100 < B20 < P20 < DMF20. In addition, the comprehensive influence was that blending oxygenated fuels would be a benefit for developing fuel atomization and the air–fuel mixture of conventional diesel fuel. There are only very few efforts focused on macroscopic spray characteristics of various oxygenated diesel fuels and perhaps no investigation simultaneously involved in the n‐butanol, pine oil, 2,5‐dimethylfuran, and diesel blended fuels through experimental measurement with the combined effect of fuel property and injection pressure. With that in mind, the objective of this study is seeking to bridge the gap identified in the literature. The investigation confirmed the benefit of oxygenated fuel addition as a useful means to improve spray development which strengthens the combustion more effectively and rapidly.

To improve the exhaust emissions of n-butanol/diesel blends fueled HCCI engines, the influence of intake temperature (T in ) on the HC, CO, and NO x emissions was studied by bench tests on λ of 2.5, engine speed of 1000 r/min under the conditions with the blending ratio of B50 and B90. Experimental results show that the HC and CO decline as T in rises. At the same T in , the CO and HC of B90 are lower than B50. When the intake temperature is lower than 150°C, the NO x emissions are almost zero.

Biobutanol is a promising biofuel due to the close resemblance of its fuel properties to gasoline, and it is produced via acetone-butanol-ethanol (ABE) fermentation using Clostridium species. However, lignin in the crystalline structure of the lignin-cellulose-hemicellulose biomass complex is not readily consumed by the Clostridium; thus, pretreatment is required to degrade this complex. During pretreatment, some fractions of cellulose and hemicellulose are converted into fermentable sugars, which are further converted to ABE. However, a major setback resulting from common pretreatment processes is the formation of sugar and lignin degradation compounds, including weak acids, furan derivatives, and phenolic compounds, which have inhibitory effects on the Clostridium. In addition, butanol concentration above 13 g/L in the fermentation broth is itself toxic to most Clostridium strain(s). This review summarizes the current state-of-the-art knowledge on the formation of microbial inhibitors during the most common lignocellulosic biomass pretreatment processes. Metabolic effects of inhibitors and their impacts on ABE production, as well as potential solutions for reducing inhibitor formation, such as optimizing pretreatment process parameters, using inhibitor tolerant strain(s) with high butanol yield ability, continuously recovering butanol during ABE fermentation, and adopting consolidated bioprocessing, are also discussed.

Global energy and environmental problems have stimulated increased efforts towards synthesizing biofuels from renewable resources. Compared to the traditional biofuel, ethanol, higher alcohols offer advantages as gasoline substitutes because of their higher energy density and lower hygroscopicity. In addition, branched-chain alcohols have higher octane numbers compared with their straight-chain counterparts. However, these alcohols cannot be synthesized economically using native organisms. Here we present a metabolic engineering approach using Escherichia coli to produce higher alcohols including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol from glucose, a renewable carbon source. This strategy uses the host's highly active amino acid biosynthetic pathway and diverts its 2-keto acid intermediates for alcohol synthesis. In particular, we have achieved high-yield, high-specificity production of isobutanol from glucose. The strategy enables the exploration of biofuels beyond those naturally accumulated to high quantities in microbial fermentation.

The results indicated that the aldehydes and ketones were more inhibitory than the corresponding acids and alcohols.[...]the identification and detoxification of aldehydes and ketones in the prehydrolysates are critically needed in biofuels fermentation.[...]a combination approach is needed to detoxify the prehydrolysates for ABE fermentation.[...]integration of overliming and AC treatment could be more effective to remove both furans and phenolic compounds (aromatic monomers and dimers).According to the HPLC analysis, the prehydrolysates contained glucose (10.85 g L−1), xylose (8.93 g L−1), galactose (1.04 g L−1), arabinose (0.64 g L−1), mannose (1.94 g L−1), and sugar degradation compounds including formic acid (1.15 g L−1), acetic acid (6.08 g L−1), levulinic acid (1.12 g L−1), HMF (0.63 g L−1) and furfural (4.94 g L−1).

The global energy crisis and limited supply of petroleum fuels have rekindled the interest in utilizing a sustainable biomass to produce biofuel. Butanol, an advanced biofuel, is a superior renewable resource as it has a high energy content and is less hygroscopic than other candidates. At present, the biobutanol route, employing acetone–butanol–ethanol (ABE) fermentation in Clostridium species, is not economically competitive due to the high cost of feedstocks, low butanol titer, and product inhibition. Based on an analysis of the physiological characteristics of solventogenic clostridia, current advances that enhance ABE fermentation from strain improvement to product separation were systematically reviewed, focusing on: (1) elucidating the metabolic pathway and regulation mechanism of butanol synthesis; (2) enhancing cellular performance and robustness through metabolic engineering, and (3) optimizing the process of ABE fermentation. Finally, perspectives on engineering and exploiting clostridia as cell factories to efficiently produce various chemicals and materials are also discussed.

Clostridium spp. produce n-butanol in the acetone/butanol/ethanol process. For sustainable industrial scale butanol production, a number of obstacles need to be addressed including choice of feedstock, the low product yield, toxicity to production strain, multiple-end products and downstream processing of alcohol mixtures. This review describes the use of lignocellulosic feedstocks, bioprocess and metabolic engineering, downstream processing and catalytic refining of n-butanol.

At present, diminishing oil resources and increasing environmental concerns have led to a shift toward the production of alternative biofuels. In the last few decades, butanol, as liquid biofuel, has received considerable research attention due to its advantages over ethanol. Several studies have focused on the production of butanol through the fermentation from raw renewable biomass, such as lignocellulosic materials. However, the low concentration and productivity of butanol production and the price of raw materials are limitations for butanol fermentation. Moreover, these limitations are the main causes of industrial decline in butanol production. This study reviews butanol fermentation, including the metabolism and characteristics of acetone-butanol-ethanol (ABE) producing clostridia. Furthermore, types of butanol production from biomass feedstock are detailed in this study. Specifically, this study introduces the recent progress on the efficient butanol production of “designed” and modified biomass. Additionally, the recent advances in the butanol fermentation process, such as multistage continuous fermentation, metabolic flow change of the electron carrier supplement, continuous fermentation with immobilization and recycling of cell, and the recent technical separation of the products from the fermentation broth, are described in this study.

N-butanol is well known to be a flammable and harmful liquid that is a potential threat to human health and property. Therefore, it is important to monitor the concentration of n-butanol in the surroundings. The need for highly efficient toxic gas detection is urgent and has been driving the research on gas sensors for practical applications. Molybdenum disulfide (MoS 2 ) has been attracting significant interest for gas detection at room temperature. Herein, we report biofunctionalized magnetic nanoparticles incorporated MoS 2 for sensing n-butanol. The biosynthesized magnetite nanoparticles (CT-Fe 3 O 4 ) were synthesized by the addition of Cinnamomum Tamala (CT) leaf extract, and subsequently, the nanocomposite was synthesized using a hydrothermal method. Highly sensitive sensors based on MoS 2 -CT-Fe 3 O 4 were fabricated and tested for sensing different concentrations of n-butanol. The nanocomposites showed a good sensing performance ( Δ R/R air %) of 72% towards 20 ppm of n-butanol, indicating the potential use of MoS 2 -CT-Fe 3 O 4 nanocomposite for sensing n-butanol at room temperature.