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Alkyl esters of sinapic acid were enzymatically synthesized by using hexanol CH3(CH2)5OH and palmitoyl chloride CH3(CH2)14COCl as acyl donors. The lipid oxidation retarding activities of these conjugates were determined using different methods in two lipid media; bulk flaxseed oil and its fatty acid methyl esters (FAME). Palmitoyl sinapate more efficiently slowed down the formation of primary and secondary oxidation products in both lipid media. In terms of DPPH radical scavenging activity, β‐carotene bleaching and TEAC assays, it provided higher activity compared to hexyl ester in FAME. Hexyl ester was more active in bulk oil in terms of antioxidant activity analyses. The alkyl side chain length of these molecules had an impact on their antioxidative activity and this effect differed according to the environment in which they were used. The conjugates remained more stable on storage compared to the phenolic compounds originally found in the oil samples. [ABSTRACT FROM AUTHOR]

Utilizing syngas components CO, CO2, and H2 to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, and the creation of cost-effective media are crucial. This study compared syngas fermentation capabilities of three novel strains (Clostridium carboxidivorans P20, C. ljungdahlii P14, and C. muellerianum P21) with existing strains (C. ragsdalei P11 and C. carboxidivorans P7) in three medium formulations. Fermentations in 250-mL bottles were conducted at 37 °C using H2:CO2:CO (30:30:40) using P11, P7, and corn steep liquor (CSL) media. Results showed that P11 and CSL media facilitated higher cell mass, alcohol titer, and gas conversion compared to the P7 medium. Strains P7, P14, and P20 formed 1.4- to 4-fold more total alcohols in the CSL medium in comparison with the P7 medium. Further, strain P21 produced more butanol (0.9 g/L) and hexanol (0.7 g/L) in the medium with CSL, offering cost advantages over P7 and P11 media containing yeast extract. Enhancing strain activity and selectivity in converting syngas into C4 and C6 alcohols requires further development, medium formulation improvements, and characterization, particularly for the new strain P21. [ABSTRACT FROM AUTHOR]

Hexanol is a volatile alcohol and a major component of plant essential oils (EOs). However, the antibacterial activity of hexanol vapor has not been well studied. This study aimed to evaluate the antibacterial activity of hexanol. In this study, seven food-related bacteria were exposed to 1-, 2- or 3-hexanol vapor on agar media to evaluate their growth. Additionally, the total viable counts in three vegetables when exposed to 1-hexanol vapor were measured. The results showed that 1-hexanol exhibited antibacterial effects against Gram-negative bacteria but did not affect Gram-positive bacteria. However, compounds 2- and 3-hexanol did not show antimicrobial activity against any bacteria. For the vegetables, exposure to 1-hexanol vapor decreased the total viable bacterial counts in cabbage and carrot and inhibited bacterial growth in eggplants. In cabbage, 1-hexanol vapor at concentrations over 50 ppm decreased the total viable count within 72 h, and 25 ppm of vapor showed bacteriostatic activity for 168 h. However, 1-hexanol vapor also caused discoloration in cabbage. In summary, 1-hexanol has the potential to act as an antibacterial agent, but further studies are required for practical use. Moreover, the study results may help determine the antimicrobial activity of various EOs in the future. [ABSTRACT FROM AUTHOR]

Abstract Background The replacement of fossil fuels and petrochemicals with sustainable alternatives is necessary to mitigate the effects of climate change and also to counteract diminishing fossil resources. Acetogenic microorganisms such as Clostridium spp. are promising sources of fuels and basic chemical precursors because they efficiently utilize CO and CO2 as carbon source. However the conversion into high titers of butanol and hexanol is challenging. Results Using a metabolic engineering approach we transferred a 17.9-kb gene cluster via conjugation, containing 13 genes from C. kluyveri and C. acetobutylicum for butanol and hexanol biosynthesis, into C. ljungdahlii. Plasmid-based expression resulted in 1075 mg L−1 butanol and 133 mg L−1 hexanol from fructose in complex medium, and 174 mg L−1 butanol and 15 mg L−1 hexanol from gaseous substrate (20% CO2 and 80% H2) in minimal medium. Product formation was increased by the genomic integration of the heterologous gene cluster. We confirmed the expression of all 13 enzymes by targeted proteomics and identified potential rate-limiting steps. Then, we removed the first-round selection marker using CRISPR/Cas9 and integrated an additional 7.8 kb gene cluster comprising 6 genes from C. carboxidivorans. This led to a significant increase in the hexanol titer (251 mg L−1) at the expense of butanol (158 mg L−1), when grown on CO2 and H2 in serum bottles. Fermentation of this strain at 2-L scale produced 109 mg L−1 butanol and 393 mg L−1 hexanol. Conclusions We thus confirmed the function of the butanol/hexanol biosynthesis genes and achieved hexanol biosynthesis in the syngas-fermenting species C. ljungdahlii for the first time, reaching the levels produced naturally by C. carboxidivorans. The genomic integration strain produced hexanol without selection and is therefore suitable for continuous fermentation processes.

Hexanol is a volatile alcohol and a major component of plant essential oils (EOs). However, the antibacterial activity of hexanol vapor has not been well studied. This study aimed to evaluate the antibacterial activity of hexanol. In this study, seven food-related bacteria were exposed to 1-, 2- or 3-hexanol vapor on agar media to evaluate their growth. Additionally, the total viable counts in three vegetables when exposed to 1-hexanol vapor were measured. The results showed that 1-hexanol exhibited antibacterial effects against Gram-negative bacteria but did not affect Gram-positive bacteria. However, compounds 2- and 3-hexanol did not show antimicrobial activity against any bacteria. For the vegetables, exposure to 1-hexanol vapor decreased the total viable bacterial counts in cabbage and carrot and inhibited bacterial growth in eggplants. In cabbage, 1-hexanol vapor at concentrations over 50 ppm decreased the total viable count within 72 h, and 25 ppm of vapor showed bacteriostatic activity for 168 h. However, 1-hexanol vapor also caused discoloration in cabbage. In summary, 1-hexanol has the potential to act as an antibacterial agent, but further studies are required for practical use. Moreover, the study results may help determine the antimicrobial activity of various EOs in the future.

Since their first industrial application in the acetone-butanol-ethanol (ABE) fermentation in the early 1900s, Clostridia have found large application in biomass biorefining. Overall, their fermentation products include organic acids (e.g., acetate, butyrate, lactate), short chain alcohols (e.g., ethanol, n-butanol, isobutanol), diols (e.g., 1,2-propanediol, 1,3-propanediol) and H 2 which have several applications such as fuels, building block chemicals, solvents, food and cosmetic additives. Advantageously, several clostridial strains are able to use cheap feedstocks such as lignocellulosic biomass, food waste, glycerol or C1-gases (CO 2 , CO) which confer them additional potential as key players for the development of processes less dependent from fossil fuels and with reduced greenhouse gas emissions. The present review aims to provide a survey of research progress aimed at developing Clostridium -mediated biomass fermentation processes, especially as regards strain improvement by metabolic engineering., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Ponsetto, Sasal, Mazzoli, Valetti and Gilardi.)

Background: The replacement of fossil fuels and petrochemicals with sustainable alternatives is necessary to mitigate the effects of climate change and also to counteract diminishing fossil resources. Acetogenic microorganisms such as Clostridium spp. are promising sources of fuels and basic chemical precursors because they efficiently utilize CO and CO2 as carbon source. However the conversion into high titers of butanol and hexanol is challenging. Results: Using a metabolic engineering approach we transferred a 17.9-kb gene cluster via conjugation, containing 13 genes from C. kluyveri and C. acetobutylicum for butanol and hexanol biosynthesis, into C. ljungdahlii. Plasmid-based expression resulted in 1075 mg L−1 butanol and 133 mg L−1 hexanol from fructose in complex medium, and 174 mg L−1 butanol and 15 mg L−1 hexanol from gaseous substrate (20% CO2 and 80% H2) in minimal medium. Product formation was increased by the genomic integration of the heterologous gene cluster. We confirmed the expression of all 13 enzymes by targeted proteomics and identified potential rate-limiting steps. Then, we removed the first-round selection marker using CRISPR/Cas9 and integrated an additional 7.8 kb gene cluster comprising 6 genes from C. carboxidivorans. This led to a significant increase in the hexanol titer (251 mg L−1) at the expense of butanol (158 mg L−1), when grown on CO2 and H2 in serum bottles. Fermentation of this strain at 2-L scale produced 109 mg L−1 butanol and 393 mg L−1 hexanol. Conclusions: We thus confirmed the function of the butanol/hexanol biosynthesis genes and achieved hexanol biosynthesis in the syngas-fermenting species C. ljungdahlii for the first time, reaching the levels produced naturally by C. carboxidivorans. The genomic integration strain produced hexanol without selection and is therefore suitable for continuous fermentation processes. [ABSTRACT FROM AUTHOR]

Background: The replacement of fossil fuels and petrochemicals with sustainable alternatives is necessary to mitigate the effects of climate change and also to counteract diminishing fossil resources. Acetogenic microorganisms such as Clostridium spp. are promising sources of fuels and basic chemical precursors because they efficiently utilize CO and CO2 as carbon source. However the conversion into high titers of butanol and hexanol is challenging. Results: Using a metabolic engineering approach we transferred a 17.9-kb gene cluster via conjugation, containing 13 genes from C. kluyveri and C. acetobutylicum for butanol and hexanol biosynthesis, into C. ljungdahlii. Plasmid-based expression resulted in 1075 mg L−1 butanol and 133 mg L−1 hexanol from fructose in complex medium, and 174 mg L−1 butanol and 15 mg L−1 hexanol from gaseous substrate (20% CO2 and 80% H2) in minimal medium. Product formation was increased by the genomic integration of the heterologous gene cluster. We confirmed the expression of all 13 enzymes by targeted proteomics and identified potential rate-limiting steps. Then, we removed the first-round selection marker using CRISPR/Cas9 and integrated an additional 7.8 kb gene cluster comprising 6 genes from C. carboxidivorans. This led to a significant increase in the hexanol titer (251 mg L−1) at the expense of butanol (158 mg L−1), when grown on CO2 and H2 in serum bottles. Fermentation of this strain at 2-L scale produced 109 mg L−1 butanol and 393 mg L−1 hexanol. Conclusions: We thus confirmed the function of the butanol/hexanol biosynthesis genes and achieved hexanol biosynthesis in the syngas-fermenting species C. ljungdahlii for the first time, reaching the levels produced naturally by C. carboxidivorans. The genomic integration strain produced hexanol without selection and is therefore suitable for continuous fermentation processes. [ABSTRACT FROM AUTHOR]

Recovery of energy from waste is appealing as it meets the energy demand and minimize the problems associated with waste management. Biodiesel derived from waste cooking oil was used in this study along with 1-propanol and 1-hexanol to make a comparative assessment of the alcohol addition on different diesel engine characteristics. Experimental trials were carried out by utilizing two ternary blends with 20% by volume of higher alcohols (propanol & hexanol), 30% by volume of biodiesel and 50% by volume of diesel. Later, the results were compared with binary blend of 50% by volume of diesel and 50% by volume of biodiesel (D50B50), pure diesel (D100) and biodiesel (B100). Results divulge that ignition delay period got longer for both Pr20 blend and HX20 blend which resulted in a 2% and 1% increase in peak cylinder pressure and 26% and 15% increase in peak heat release rate respectively against D50B50 blend operation. In comparison with the binary blend, the engine brake thermal efficiency improved by 3% and deteriorated by 2% against hexanol and propanol blend respectively. The NOx emission aggravated with ternary blends, nearly 8% higher NOx emission was observed for propanol blend when compared to hexanol blend. Both smoke opacity and carbon monoxide emission reduced, while unburnt hydrocarbon emission was on the higher side with the introduction of alcohol. It is concluded from the observations that the HX20 blend was found to be optimal in terms of improved engine performance and emission characteristics. [ABSTRACT FROM AUTHOR]

The production of hexanol from syngas by acetogens has gained attention as a replacement for petroleum-derived hexanol, which is widely used in the chemical synthesis and plastic industries. However, acetogenic bacteria generally produce C2 compounds (e.g., acetate and ethanol) as the main products. In this study, the gas fermentation conditions favorable for hexanol production were investigated at different temperatures (30–37°C) and CO gas contents (30–70%) in batch gas fermentation. Hexanol production increased from 0.02 to 0.09 g/L when the cultivation temperature was lowered from 37 to 30°C. As the CO content increased from 30 to 70%, the CO consumption rate and hexanol production (yield, titer, and ratio of C6 compound to total products) increased with the CO content. When 70% CO gas was repeatedly provided by flushing the headspace of the bottles at 30°C, the total alcohol production increased to 4.32 g/L at the expense of acids. Notably, hexanol production (1.90 g/L) was higher than that of ethanol (1.20 g/L) and butanol (1.20 g/L); this is the highest level of hexanol produced in gas fermentation to date and the first report of hexanol as the main product. Hexanol production was further enhanced to 2.34 g/L when 2 g/L ethanol was supplemented at the beginning of 70% CO gas refeeding fermentation. Particularly, hexanol productivity was significantly enhanced to 0.18 g/L/day while the supplemented ethanol was consumed, indicating that the conversion of ethanol to acetyl-CoA and reducing equivalents positively affected hexanol production. These optimized culture conditions (gas fermentation at 30°C and refeeding with 70% CO gas) and ethanol supplementation provide an effective and sustainable approach for bio-hexanol production.

Studies on the usage of gasoline–alcohol blends as an alternative fuel in spark-ignition engines have recently gained momentum. In the present research, energy, exergy, environmental, enviroeconomic, exergoenvironmental, and exergoenviroeconomic analyses were conducted with the performance and emission values acquired by utilizing gasoline, gasoline–heptanol, and gasoline–hexanol fuels (G100, HEX5-20, and HP5-20) as a fuel under different powers at a constant speed of 1600 rpm in a single-cylinder four-stroke spark-ignition engine. As the ratio of alcohol in fuel blends increases, fuel consumption also increases. NOX emission is higher, and CO and HC emissions are lower in alcohol-based fuel blends than G100 fuel. The highest thermal efficiency is 41.09% in G100 fuel at a power of 5 kW. As the ratio of alcohol in fuel blends increases, thermal efficiency decreases. The highest exergy destruction and entropy generation were determined to be 6.25 kW and 0.02134 kW/K, respectively, in HP20 fuel at a power of 5 kW. Entropy generation increases with an increase in the ratio of alcohol in alcohol-based fuels. HEX20 and HP20 fuels produce 25% and 30% more entropy, respectively, compared to G100 fuel. The mass and financial costs of the damage caused by the CO2 emission of fuels to the environment were determined by conducting four different analyses using energy and exergy analysis data. According to the exergoenvironmental and exergoenviroeconomic analyses, HP20 fuel reached the highest environmental pollution values of 4538.19 kg CO2/month and 65.804 $/month, respectively. The environmental cost of the CO2 emission released from the exhaust to the atmosphere is higher in alcohol-based fuels than G100 fuel. As a result of all analyses, it was concluded that hexanol and heptanol could be alternative fuels in spark-ignition engines under particular conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • PdCu, Pd and Cu nanoparticles were fabricated on the Al 2 O 3 surface. • The M0-Al 2 O 3 sites are active in conversion of ethanol to α-alcohols. • Cu0-Al 2 O 3 sites possess low activity and high stability. • Pd0-Al 2 O 3 sites possess high activity and low stability. • Cu0-Pd0-Al 2 O 3 sites possess high activity and stability. PdCu/Al 2 O 3 (Pd = 0.1 wt.%, Cu = 0.1 wt.%) catalyst and its monometallic analogues (Pd/Al 2 O 3 and Cu/Al 2 O 3) were prepared by combination of deposition-precipitation and impregnation methods. The structure of the catalysts was studied by means of XRD, TEM, EDS, TPD-NH 3 , and DRIFTS. In a standard run (275 ○C, 5 h), Cu/Al 2 O 3 converts 11 % of ethanol to α-alcohols with 0.6 % selectivity, whereas Pd/Al 2 O 3 converts 24 % of ethanol to α-alcohols with 70 % selectivity. The high performance of Pd/Al 2 O 3 was attributed to the catalysis on the Pd°-Al 2 O 3 interfaces. After 3 sequential runs, the activity of Pd/Al 2 O 3 decreases by 98 %. It was explained by blocking of Pd° sites in Pd/Al 2 O 3 by CO molecules produced in side reactions. Modification of Pd/Al 2 O 3 with Cu species results in the formation of PdCu/Al 2 O 3 catalyst containing PdCu alloy particles with the size of 4 nm. This leads to an increased durability of bimetallic sample, because of suppressing CO sorption on Pd° sites in alloy particles. As a result, for the PdCu/Al 2 O 3 catalyst, sustained and high conversion (41 %) accompanied by high selectivity to α-alcohols (91 %) was observed in 20 sequential runs. [ABSTRACT FROM AUTHOR]

Energy hotspots for the production of vanillin from Kraft lignin are identified and process improvements are proposed and rigorously simulated. The hotspots identified and addressed are related to the flowrate of methanol used as solvent and recycled in the process. Several alternative process designs containing fewer distillation columns and able to reduce the overall energy consumption are proposed. Recycling aqueous methanol, a distillation column is not required and the overall energy consumption is halved compared to the available literature (i.e. 42 %). In addition, based on a literature review and the screening of suitable solvents used for the liquid-liquid extraction of vanillin from the main product stream, the use of aliphatic alcohols such as hexanol is proposed as an optimal and underexplored solution. Their physicochemical properties allow for the elimination of the acidification step that takes place during the feed preparation stage at the beginning of the process. In this way, the process design can be simplified further. Two distillation columns are not required and the overall energy consumption of the process is reduced to 23% compared to previous studies. The proposed Kraft-lignin-based vanillin production process improvements contribute to the development and competitiveness enhancement of biomass-based vanillin production processes, which are currently in need of further refinement compared to the more mature petrochemical-based processes, but at the same time have the potential to be more sustainable, cleaner and energetically efficient.

[Display omitted] By combining the experimental small- and wide-angle x-ray scattering (SWAXS) method with molecular dynamics simulations and the theoretical 'complemented-system approach' it is possible to obtain detailed information about the intra- and inter-molecular structure and dynamics of the solvation and hydration of the surfactant in organic and mixed solvents, e.g. , of the nonionic surfactant Brij 35 (C 12 E 23) in alcohols and aqueous alcohol-rich ternary systems. This first application of the complemented-system approach to the surfactant system will promote the use of this powerful methodology that is based on experimental and calculated SWAXS data in studies of colloidal systems. By applying high-performance computing systems, such an approach is readily available for studies in the colloidal domain. SWAXS experiments and MD simulations were performed for binary Brij 35/alcohol and ternary Brij 35/water/alcohol systems with ethanol, n -butanol and n -hexanol as the organic solvent component at 25 °C. We confirmed the presence of solvated Brij 35 monomers in the studied organic media, revealed their preferential hydration and discussed their structural and dynamic features at the intra- and inter-molecular levels. Anisotropic effective surfactant molecular conformations were found. The influence of the hydrophobicity of the organic solvent on the hydration phenomena of surfactant molecules was explained. [ABSTRACT FROM AUTHOR]

Background and Aims: The presence of matter other than grapes (MOG) is common in the winemaking process when sorting equipment is not utilised. Experimental wines were made to examine the effect of MOG on the sensory profile and chemical composition of wine. Methods and Results: A Shiraz wine made without MOG was compared to fermentations with grape leaves, grape stalks (rachis) and peduncles (the stalk connecting the bunch to the vine) added at amounts at or slightly above those found in a commercial harvest bin. Fifty‐one volatile aroma compounds were quantified in the wines, and sensory descriptive analysis was applied. The wine made with leaves added was rated by the sensory panel similar to the Control and was significantly higher only in positive aromas such as 'confectionery' and 'red fruit' likely due to a higher concentration of hexanol and (Z)‐3‐hexen‐1‐ol. The addition of peduncles slightly enhanced 'green' aroma and flavour. The rachis treatment was high in 'green capsicum/green stalks' attributes, as well as astringency, and was high in methoxypyrazines. Conclusions: The inclusion of different types of MOG during fermentation can alter the sensory profile and chemical composition of Shiraz wines in varying ways, including extraction of methoxypyrazines from the rachis, resulting in notable 'green' attributes. Significance of the Study: The inclusion of MOG is unavoidable in common winemaking practices, especially with the use of mechanical harvesting. Determining the influence of MOG on the volatile composition of the finished wine is an important step in manipulating wine style. [ABSTRACT FROM AUTHOR]

The oils extracted from the waste plastic can be an admirable alternate for the compression ignition engines nevertheless they capitulate upper smoke emissions along with deprived performance when compared with diesel. The extraction of waste plastic oil (WPO) is attained through pyrolysis. The impact of accumulating a constituent hexanol (H), a biologically available biofuel is assessed. Three ternary mixtures, DE50%-WPO40%-H10%, DE50%-WPO30%- H20% and DE50%-WPO20%-H30% has been deliberately primed for utilizing mutually a cast-off element (WPO maximum of 40%) along with a non-conventional part (hexanol maximum of 30%). The performance characteristics and emission factors of C.I engine fuelled with the above mix were assessed. The output specifies that hexanol inclusion makes significant reduction in smoke emission in addition to privileged HC emission in contrast to diesel. Inclusion of 10% hexanol in volume with WPO and diesel mixture retards the NOx emission considerably whilst match up to WPO as well as diesel individually. In spite of this, NOx emission is superior than the subsequent WPO with increased degree of hexanol converges. Brake thermal efficiency of the engine increases by way of escalating the hexanol portion in the blend while comparing with WPO. The fuel spending of concoction has been established to be reduced while compared to WPO. DE50%-WPO40%-H10% concoction showed a reduced amount of NOx as well as smoke emission. [ABSTRACT FROM AUTHOR]

In this study, three-dimensional Bödewadt hybrid nanofluid flow has been investigated. Base fluids are water and hexanol which contain Fe 3 O 4 and MoS 2 . The governing nonlinear PDEs are converted into nonlinear ODEs and the nonlinear equations are solved by the homotopy perturbation method (HPM). The effects of nanoparticle volume fraction, Eckert number, base fluid and shape factor on entropy generation, Nusselt number, skin friction coefficient and Bejan number have been studied. Entropy generation is increased with an increment in Eckert number; while, it is decreased by growth in nanoparticle volume fraction and shape factor. In a similar situation, hexanol has higher rate of irreversibility, higher Bejan number and higher Nusselt number than water. The skin friction coefficient is not a function of the Eckert number and shape factor, but it is an increasing function of nanoparticle volume fraction. In this paper, by averaging the differences of Nusselt number and skin friction coefficient between water and hexanol, it can be observed that the Nusselt number and skin friction coefficient for hexanol are 11% and 5% more than water, respectively. Indeed, in a fixed situation, hexanol-based fluid flows have higher heat transfer and drag than water-based fluid flows. [ABSTRACT FROM AUTHOR]

• Mixed metal oxide derived from hydrotalcites was explored for hexanol conversion. • Mg-Cr-Mo oxide showed both hydrogenated and dehydrated products. • MgAlMo600 and MgFeMo600 yield more than 80 % of the dehydrated product. • Uniform dispersion of active sites on MgFeMo600 showed 85 % conversion of hexanol. • Catalysts showed steady state conversion with a time-on-stream of more than 8 hr. A series of mixed metal oxides derived from hydrotalcites (HT) were explored for the dehydration of hexanol in the vapour phase. The influence of framework cations (MgFe, MgAl, and MgCr), interlayer anions (carbonate, molybdate), and calcination temperature on the acid-base and textural properties of hydrotalcites was systematically followed. The powder XRD confirmed the formation of a uniformly dispersed mixed metal oxide phase. The incorporation of iron or chromium in the framework leads to a decrease in surface acidity compared to aluminium, as evident from temperature-programmed desorption of ammonia (NH 3 -TPD) profiles. The incorporation of molybdate ions leads to moderate basicity with an increase in the number of basic sites, as evident from the CO 2 -TPD. The developed molybdate-free and molybdate-intercalated HT materials were investigated for the hexanol dehydration process. Among the molybdate-free materials, MgAl600 showed better conversion (77 %) with 89 % selectivity to hexene at 350 °C. The calcined molybdate containing MgFe (MgFeMo600) showed an improved conversion of 85 % with 83 % selectivity to hexene. The uniform dispersion of active sites on the surface of HT and the moderate acid-base properties of MgFeMo600 facilitate better activity and stability over a time on stream of 5 h. [Display omitted] [ABSTRACT FROM AUTHOR]

Anaerobic fermentation technology enables the production of medium chain carboxylates and alcohols through microbial chain elongation. This involves steering reactor microbiomes to yield desired products, with CO 2 supply playing a crucial role in controlling ethanol-based chain elongation and facilitating various bioprocesses simultaneously. In the absence of CO 2 supply (Phase I), chain elongation predominantly led to n-caproate with a high selectivity of 96 Cmol%, albeit leaving approximately 80% of ethanol unconverted. During this phase, C. kluyveri and Proteiniphilum -related species dominated the reactors. In Phase II, with low CO 2 input (2.0 NmL L -1  min -1 ), formation of n-butyrate, butanol, and hexanol was stimulated. Increasing CO 2 doses in Phase III (6 NmL L -1  min -1 ) led to CO 2 utilization via homoacetogenesis, coinciding with the enrichment of Clostridium luticellarii , a bacterium that can use CO 2 as an electron acceptor. Lowering CO 2 dose to 0.5 NmL L -1  min -1 led to a shift in microbiome composition, diminishing the dominance of C. luticellarii while increasing C. kluyveri abundance. Additionally, other Clostridia , Proteiniphilum , and Lactobacillus sakei -related species became prevalent. This decrease in CO 2 load from 6 to 0.5 NmL L -1  min -1 minimized excessive ethanol oxidation from 30%-50% to 0%-3%, restoring a microbiome favoring net n-butyrate consumption and n-caproate production. The decreased ethanol oxidation coincided with the resurgence of hydrogen formation at partial pressures above 1%. High concentrations of butyrate, caproate, and ethanol in the reactor, along with low acetate concentration, promoted the formation of butanol and hexanol. It is evident that CO 2 supply is indispensable for controlling chain elongation in an open culture and it can be harnessed to stimulate higher alcohol formation or induce CO 2 utilization as an electron acceptor., Competing Interests: Author DL was employed by the ChainCraft B.V. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from ChainCraft B.V. The funder had the following involvement in the study: study design, collection, analysis, interpretation of data and the writing of this article., (Copyright © 2024 de Leeuw, van Willigen, Vrauwdeunt and Strik.)

Abstract In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel. Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10% (by volume) of hexanol and 90% (by volume) neat cashew nut shell biodiesel was referred to as CNSBD900H100 and fuel comprising 20% (by volume) of hexanol and 80% (by volume) of neat cashew nut shell biodiesel was referred to as CNSBD800H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at 10% and 20% (by volume) to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine.

Pentanol and Hexanol are two excellent biofuels that could be derived from lignocellulosic biomass feedstock without disturbing food-based sources. The present study utilizes these two alcohols as blend constituents with diesel by up to 30% by vol. (designated as Pen30 and Hex30) in a DI diesel engine subject to modifications in injection timing (early and late) and intake air dilution through EGR (up to 30%). The modifications were intended to obtain an optimum performance of the engine. The combustion and performance characteristics of this engine were analyzed with reference to diesel operation. The results indicated that Pen30 blend experienced longer ignition delays, higher peaks of pressure and heat release rates (HRR) than Hex30 at all conditions of EGR. The premixed combustion phasing with the blends were more enhanced followed by numerous HRR spikes during diffusion phasing indicating better combustion. Both the blends delivered better brake thermal efficiencies but with a penalty in fuel consumption. Pen30 delivered better BTE but consumed more than Hex30. NOx emissions of the blends were of the order: Diesel > Pen30 > Hex30. Smoke densities of the blends were of the order: Diesel > Hex30 > Pen30. HC emissions of the blends were of the order: Pen30 > Hex30 > Diesel. CO emissions of the blends followed the trends of smoke emissions. Both these alcohols could be excellent partial substitutes for diesel with minor modifications to the engine subject to long-term tests on durability. [ABSTRACT FROM AUTHOR]

The present work details the effects of injection of higher order alcohols, namely hexanol (Hex) and octanol (Oct) as secondary fuels in a CI engine. The last decade has seen an exponential increase in the carbon emission chief of which have been contributed by fossil fuels. Vegetable oils provide a viable alternative to the current scenario as they can be synthesized easily from nature and can be readily adapted for use in CI engines. Neem oil (NO) is non-edible and widely available and hence taken as a base fuel for this research. The poor properties of neem oil were improved by the addition of novel low viscous biofuel, namely wintergreen oil (WGO). During the course of this research work, a blend containing a mixture of 50% of neat neem oil and 50% of wintergreen oil (NO50-WGO50) was optimized based on trial tests and taken as pilot fuel while Hex and Oct were injected along with intake air as secondary fuels. The alcohols were injected into the engine successively in the 10%, 20%, and 30% (by mass) ratios. Experiments were conducted in a single-cylinder CI engine fabricating 5.2-kW power at a constant speed of 1500 rpm at varying load conditions. It is observed that inferior performance of NO led to more smoke, HC, and CO in comparison to diesel at all the loads and these are improved with NO50-WGO50 blend. Nevertheless, a minor increase in NOx emission was perceived with the blend. Addition of higher order alcohol promoted reduction of both NOx and smoke emission without affecting performance. Among the various combinations, NO50-WGO50 + Hex30 and Oct30 reduced NOx emission by 12% and 9.5% and smoke emission by 13% and 19% respectively. These results are on par with the diesel performance and emission characteristics. [ABSTRACT FROM AUTHOR]

The interest of using alternative fuels in Diesel engines has been accelerated exponentially due to a foreseen scarcity in world petroleum reserves and restrictions on exhaust emissions. Alcohol which is bio-based renewable and oxygenated fuel provides a suitable alternate fuel for internal combustion engines. In this regard, exploration of potential for higher alcohols in automotive application is needed. Long chain alcohols such as pentanol and hexanol despite their analogous properties have rarely been inspected. The n-hexanol, the longer chain alcohol is used to be fueled with diesel. These oxygenated additives allow the fuel to increase combustion efficiency due to the presence of oxygen. In the present investigation, two blends of hexanol and diesel were prepared. All the blends were found to be homogenous and stable. The brake thermal efficiency for all the blends was observed to be slightly higher in comparison to neat diesel. The maximum brake thermal efficiency was obtained with B20 blend. Similarly, minimum total fuel consumption was obtained for B20 blend while rest of the blend showed a reduction in total fuel consumption. The CO emissions were found to get reduced with increase in hexanol percentage in the blends. The HC emissions were observed to increase as the percentage of hexanol increases on the blend. The NOx emissions increased with increase in engine load for all test fuels. Finally, concluded that a blend of B20% hexanol in diesel will result in better engine performance and emissions of CO2, CO, and NOx. [ABSTRACT FROM AUTHOR]

• Hexanol is used as additives with Calophyllum Inophyllum biodiesel. • Hexanol concentration is varied as 10%, 15%, 20%, 30% and 40% on volume basis. • Hexanol shows improved efficiency with less fuel consumption for higher fractions. • Addition of higher alcohol reduces the HC, CO, NOx and smoke emissions. In the present work, an experiment on ternary blends made of n-hexanol, diesel and Calophyllum Inophyllum methyl ester was conducted to compare the emission, performance and combustion characteristics to that of pure diesel and Calophyllum Inophyllum methyl ester. In the present research work, all the ternary blends were prepared by keeping the diesel weight percentage as a constant at 50% by volume, the Calophyllum Inophyllum methyl ester and hexanol concentrations were varied by volume and the developed blends were used for the comprehensive analysis. The brake thermal efficiency was observed to be significantly higher for the hexanol blends; especially for 40% hexanol is closer to that of pure diesel at elevated brake mean effective pressures. Also, the brake specific fuel consumptions are observed to be lower than that of pure CIME. Emissions such as hydrocarbon, smoke opacity and carbon monoxide were found to be significantly lower than the diesel. However, the NOx and carbon dioxide emissions for alcohol blends remained marginally higher compared to diesel. A significant improvement in the combustion characteristics such as the in-cylinder pressures and net HRR figures were observed when compared to pure biodiesel. Therefore, from the results, it is recommended that the 30% and 40% of n-hexanol blends with further study can suitably be a potential alternative for pure diesel. [ABSTRACT FROM AUTHOR]

Higher order alcohols, such as 1-butanol and 1-hexanol, have a large number of applications but are currently prepared from non-renewable feedstocks. Here, the ability of Thermoanaerobacter pseudoethanolicus to reduce short-chain fatty acids to their corresponding alcohols using reducing potential generated by glucose catabolism with yields between 21.0 and 61.0%. 13C-labelled acetate, 1-propionate and 1-butyrate demonstrates that exogenously added fatty acids are indeed reduced to their corresponding alcohols. This mode of producing primary alcohols from fatty acids using a thermophilic anaerobe opens the door for the production of such alcohols from low-value materials using an inexpensive source of reducing potential. Image 1 • T. pseudoethanolicus converts C3-C6 fatty acids to their corresponding alcohols. • 33.0% of 1-propionate is converted to 1-propanol during glucose fermentation. • 55.6% of 1-butyrate is converted to 1-butanol during glucose fermentation. • 33.5% of 1-hexanoate is converted to 1-hexanol during glucose fermentation. • 13C1-labelled propionate and butyrate show conversion to 1-propanol and 1-butanol. [ABSTRACT FROM AUTHOR]

Highlights • Tungsten, Selenium and pH affect syngas fermentation and alcohols/acids production. • The absence of tungsten and selenium favours the accumulation of organic acids. • The presence of tungsten and selenium stimulates acids to alcohols bioconversion. • A high pH (6.2) is preferred for bacterial growth and the production of organic acids. Abstract Clostridium carboxidivorans produces alcohols from C1 gases (CO, CO 2), converting them first into fatty acids, and subsequently into alcohols. This research identified conditions that allow to selectively produce either fatty acids or alcohols. The conversion of gases into acids and then into alcohols is catalysed by metalloenzymes, stimulated by specific trace metals. Therefore, different bioreactors were set-up, either with or without addition of tungsten (W) or selenium (Se) and at different pHs. Combining the presence of those trace metals with a low pH (5.0) allowed to accumulate high amounts of alcohols as major end products (8038 mg/L total alcohols; 3027 mg/L total acids). Instead, maintaining a higher pH (6.2), in the absence of those trace metals, allowed to selectively produce organic acids (9577 mg/L) and almost no alcohols (676 mg/L). Omitting W, but not Se, at high pH (6.2), led to a still higher concentration of acids (11303 mg/L). [ABSTRACT FROM AUTHOR]

Abstract In this research work, the four ternary blends were prepared with 30% and 40% by volume of higher alcohol (decanol and hexanol) with biodiesel while maintain 50% of diesel concentration. All ternary blends of diesel-biodiesel-higher alcohols were used in single cylinder engine and the results were compared with binary blend of 50%–50% biodiesel, pure diesel and biodiesel. It was revealed that thermal efficiency of ternary blends was higher than biodiesel and in some cases it is closer to pure diesel. In contrary, specific fuel consumption is found to lower with increase in alcohol fractions in ternary blends. Moreover, hydrocarbon, smoke, carbon monoxide emissions from alcohol-infused fuel blends were observed to be lower than both biodiesel and pure diesel. Significant reduction in oxides of nitrogen (NOx) emissions was also observed by the addition of higher alcohols to the fuel blend when compared to biodiesel fuel. It is to be noted that decanol 40% addition with diesel and biodiesel blend has shown better results in emission characteristics. Furthermore, the heat release rate and in-cylinder pressure for biodiesel were significantly lower compared to pure diesel fuels. However, addition of 40% decanol with fuel blend improved the heat release rate and in-cylinder pressure. Highlights • Hexanol and Decanol are used as additives for ternary blends preparation. • Alcohol concentration has been varied in the proportion of 30% and 40% on volume basis. • Decanol shows improved efficiency with less fuel consumption for higher fractions. • Addition of higher alcohol reduces the HC, CO, NOx and smoke emissions. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A rich medium (yeast extract) and high pH (≥6) favours biomass growth on C1-gases. • Mainly fatty acids (C2–C6) but also some alcohols accumulate during biomass growth. • Production of fatty acids stopped once biomass growth levelled off. • After reaching maximum biomass accumulation fatty acids were converted to alcohols. Abstract An anaerobic granular sludge was acclimatized to utilise CO in a continuously gas-fed stirred tank bioreactor by applying operating conditions expected to stimulate solventogenesis, i.e. the production of alcohols, and allowing to enrich for solventogenic populations. A cycle of high (6.2) and low (4.9) pH was applied in order to produce volatile fatty acids first at high pH, followed by their bioconversion into alcohols at low pH. The addition of yeast extract stimulated biomass growth, but not necessarily solventogenesis. The highest concentrations of metabolites achieved were 6.18 g/L acetic acid (30th day), 1.18 g/L butyric acid (28th day), and 0.423 g/L hexanoic acid (32nd day). Subsequently, acids were metabolized at lower pH, producing alcohols at concentrations of 11.1 g/L ethanol (43rd day), 1.8 g/L butanol (41st day) and 1.46 g/L hexanol (42nd day), confirming the successful enrichment strategy. Similarly, the enriched sludge could also convert syngas into acids and alcohols. [ABSTRACT FROM AUTHOR]

Activity of heterogeneous catalysts for synthesis of Guerbet alcohols from hexanol was evaluated. Commercial synthetic hydrotalcite (HT) was used in the aldol condensation reaction, which is a part of the Guerbet reaction network. HTs were calcined at different temperatures in order to modify their basicity and additionally, NaOH was applied in some experiments as a homogeneous base. The homogeneous base proved to be more efficient in aldol condensation experiments, while HT also performed in an acceptable way. Bi-functional metal containing HTs were synthesized by wet impregnation and co-precipitation methods employing different active metals. The materials were characterized with a number of methods, including CO2-TPD, pyridine-FTIR, nitrogen physisorption, transmission electron microscopy, SEM-EDX and XRD. Copper containing catalysts produced hexyl-hexanoate with a very high selectivity, while Ni-containing counterparts exhibited the highest selectivity towards the Guerbet alcohol. The co-precipitated catalysts were more active in the current study than the ones produced by wet-impregnation. Nevertheless, synthesis of Guerbet alcohols from hexanol with a one-pot method proved to be challenging, with the best yield of the Guerbet product in 24 h being 5%. This is proposed to be largely due to thermodynamic limitations, which was confirmed by calculations of thermodynamics. [ABSTRACT FROM AUTHOR]

This paper reports the results of an experimental investigation of heat transfer from a wickless finned heat pipe charged with different self-rewetting fluids. The geometry considered for the experiments comprises an evaporator section of length 200 mm, condenser section of length 200 mm and adiabatic section of length 100 mm. Six constant area fins are placed internally along the length of the condenser. The width of the fin is 5 mm and the thickness is 1 mm. Adding internal fins at the condenser wall gives more surface area to the vapor for heat transfer. This gives additional condensation that keeps the evaporator at safe temperatures and extends the dry out condition. Additionally, fins break the condensed liquid film and augment heat transfer. The fill ratio considered in the present study is 50 % . The self rewetting fluids considered in this work are butanol, pentanol, hexanol, and heptanol aqueous solutions. The concentrations of the self rewetting fluids are changed to study the thermal behavior of a heat pipe and the results are compared with those for water charged devices presented in literature. The thermosyphon is tested between power levels of 150 W (heat flux = 9182 W/ m 2 ) and 350 W (heat flux = 21424 W/ m 2 ). Results confirm superior thermal performance of self rewetting fluids compared to water. [ABSTRACT FROM AUTHOR]

In this study, the effect of doping hexanol into biodiesel which is from neat cashew nut shell biodiesel oil on the emissions and the performance characteristics was studied in a constant speed diesel engine. The main purpose of this work is to reduce various emissions and also to improve the performance of the diesel engine when fueled with blends of hexanol and neat cashew nut shell biodiesel. Cashew nut shell oil is not edible, and hence it can be used as a viable alternative to diesel. Cashew nut shell biodiesel is prepared by conventional transesterification. Hexanol with 99.2% purity was employed as an oxygenated additive. Experimental studies were conducted by fueling diesel as a baseline and by fueling hexanol and neat cashew nut shell biodiesel mixture. A fuel comprising 10% (by volume) of hexanol and 90% (by volume) neat cashew nut shell biodiesel was referred to as CNSBD900H100 and fuel comprising 20% (by volume) of hexanol and 80% (by volume) of neat cashew nut shell biodiesel was referred to as CNSBD800H200. This study also investigated the possibility of using pure biofuel in an unmodified naturally aspirated diesel engine. The outcome of this study showed that adding hexanol at 10% and 20% (by volume) to cashew nut shell biodiesel results in a reduction in emissions. In addition, a significant improvement in brake thermal efficiency and reduction in brake-specific fuel consumptions were achieved. Hence, it could be concluded that hexanol could be a viable and promising additive for improving the drawbacks of biodiesel when it was used to fuel an unmodified diesel engine. [ABSTRACT FROM AUTHOR]

Some clostridia produce alcohols (ethanol, butanol, hexanol) from gases (CO, CO 2 , H 2 ) and others from carbohydrates ( e.g ., glucose). C. carboxidivorans can metabolize both gases as well as glucose. However, its bioconversion profile on glucose had not been reported. It was observed that C. carboxidivorans does not follow a typical solventogenic stage when grown on glucose. Indeed, at pH 6.2, it produced first a broad range of acids (acetic, butyric, hexanoic, formic, and lactic acids), several of which are generally not found, under similar conditions, during gas fermentation. Medium acidification did not allow the conversion of fatty acids into solvents. Production of some alcohols from glucose was observed in C. carboxidivorans but at high pH rather than under acidic conditions, and the total concentration of those solvents was low. At high pH, formic acid was produced first and later converted to acetic acid, but organic acids were not metabolized at low pH. [ABSTRACT FROM AUTHOR]