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Preparation of Furfural From Xylose Catalyzed by Diimidazole Hexafluorophosphate in Microwave.

ABSTRACT: In this work, functionalized alkyl imidazolium hexafluorophosphate ILs were synthesized and characterized; then, they were applied in the conversion of xylose to furfural under the microwave method. The results showed that when C_nMF was used as a catalyst, an acidic environment was provided to promote the formation of furfural. In addition, the heating method, the solvent, and the different structures of cations in the ionic liquid influenced their catalytic activity. In an aqueous solution, the yield of furfural obtained using the microwave method was better than that of the conventional heating method, and the catalytic activity of diimidazole hexafluorophosphate was better than that of monoimidazole. Meanwhile, for the diimidazole hexafluorophosphate, the change of the carbon chain length between the imidazole rings also slightly influenced the yield. Finally, the optimal yield of 49.76% was obtained at 205°C for 8 min using 3,3'-methylenebis(1-methyl-1H-imidazol-3-ium), C₁MF, as a catalyst. Mechanistic studies suggested that the catalytic activity of C₁MF was mainly due to the combined effect of POF_n (OH)_3-n and imidazole ring. Without a doubt, the catalytic activity of C₁MF was still available after five cycles, which not only showed its excellent catalytic activity in catalyzing the xylose to prepare the biomass platform compound furfural but also could promote the application of functionalized ionic liquids.

SUBMITTER: Huang T

PROVIDER: S-EPMC8440960 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundPretreatment of lignocellulosic biomass generates a number of undesired degradation products that can inhibit microbial metabolism. Two of these compounds, the furan aldehydes 5-hydroxymethylfurfural (HMF) and 2-furaldehyde (furfural), have been shown to be an impediment for viable ethanol production. In the present study, HMF and furfural were pulse-added during either the glucose or the xylose consumption phase in order to dissect the effects of these inhibitors on energy state, redox metabolism, and gene expression of xylose-consuming Saccharomyces cerevisiae.ResultsPulsed addition of 3.9 g L-1 HMF and 1.2 g L-1 furfural during either the glucose or the xylose consumption phase resulted in distinct physiological responses. Addition of furan aldehydes in the glucose consumption phase was followed by a decrease in the specific growth rate and the glycerol yield, whereas the acetate yield increased 7.3-fold, suggesting that NAD(P)H for furan aldehyde conversion was generated by acetate synthesis. No change in the intracellular levels of NAD(P)H was observed 1 hour after pulsing, whereas the intracellular concentration of ATP increased by 58%. An investigation of the response at transcriptional level revealed changes known to be correlated with perturbations in the specific growth rate, such as protein and nucleotide biosynthesis. Addition of furan aldehydes during the xylose consumption phase brought about an increase in the glycerol and acetate yields, whereas the xylitol yield was severely reduced. The intracellular concentrations of NADH and NADPH decreased by 58 and 85%, respectively, hence suggesting that HMF and furfural drained the cells of reducing power. The intracellular concentration of ATP was reduced by 42% 1 hour after pulsing of inhibitors, suggesting that energy-requiring repair or maintenance processes were activated. Transcriptome profiling showed that NADPH-requiring processes such as amino acid biosynthesis and sulfate and nitrogen assimilation were induced 1 hour after pulsing.ConclusionsThe redox and energy metabolism were found to be more severely affected after pulsing of furan aldehydes during the xylose consumption phase than during glucose consumption. Conceivably, this discrepancy resulted from the low xylose utilization rate, hence suggesting that xylose metabolism is a feasible target for metabolic engineering of more robust xylose-utilizing yeast strains.

Project description:BackgroundPretreatment of biomass for lignocellulosic ethanol production generates compounds that can inhibit microbial metabolism. The furan aldehydes hydroxymethylfurfural (HMF) and furfural have received increasing attention recently. In the present study, the effects of HMF and furfural on redox metabolism, energy metabolism and gene expression were investigated in anaerobic chemostats where the inhibitors were added to the feed-medium.ResultsBy cultivating the xylose-utilizing Saccharomyces cerevisiae strain VTT C-10883 in the presence of HMF and furfural, it was found that the intracellular concentrations of the redox co-factors and the catabolic and anabolic reduction charges were significantly lower in the presence of furan aldehydes than in cultivations without inhibitors. The catabolic reduction charge decreased from 0.13(±0.005) to 0.08(±0.002) and the anabolic reduction charge decreased from 0.46(±0.11) to 0.27(±0.02) when HMF and furfural were present. The intracellular ATP concentration was lower when inhibitors were added, but resulted only in a modest decrease in the energy charge from 0.87(±0.002) to 0.85(±0.004) compared to the control. Transcriptome profiling followed by MIPS functional enrichment analysis of up-regulated genes revealed that the functional group "Cell rescue, defense and virulence" was over-represented when inhibitors were present compared to control cultivations. Among these, the ATP-binding efflux pumps PDR5 and YOR1 were identified as important for inhibitor efflux and possibly a reason for the lower intracellular ATP concentration in stressed cells. It was also found that genes involved in pseudohyphal growth were among the most up-regulated when inhibitors were present in the feed-medium suggesting nitrogen starvation. Genes involved in amino acid metabolism, glyoxylate cycle, electron transport and amino acid transport were enriched in the down-regulated gene set in response to HMF and furfural. It was hypothesized that the HMF and furfural-induced NADPH drainage could influence ammonia assimilation and thereby give rise to the nitrogen starvation response in the form of pseudohyphal growth and down-regulation of amino acid synthesis.ConclusionsThe redox metabolism was severely affected by HMF and furfural while the effects on energy metabolism were less evident, suggesting that engineering of the redox system represents a possible strategy to develop more robust strains for bioethanol production.

Project description:Background: Lignocellulosic biomass is a promising renewable feedstock for the microbial production of fuels. To release the major fermentable sugars such as glucose and xylose, pretreatment, hydrolysis, and subsequent conditioning of biomass feedstock are needed. During this process, many toxic compounds are produced or introduced which subsequently inhibit microbial growth and in many cases the production titer and rate. An understanding of the toxic effects of compounds found in hydrolysate on the fermentation microorganism is critical to improving biofuel yields in the process. One of the inhibitory compounds is furfural, liberated from hemicelluloses, which strongly inhibits the cell growth and ethanol production especially from xylose. Zymomonas mobilis is a capable ethanologenic bacterium with high ethanol productivity and high levels of ethanol tolerance. The development of robust biocatalyst to tolerate the lignocellulosic pretreatment inhibitors is one of the key elements for economic biofuel production. Results: In this study, the molecular responses of Z. mobilis to furfural, one major pretreatment inhibitor, were investigated using transcriptomic approaches of chip-based microarray. Furfural shock time course experiment with 3 g/L furfural supplemented when cells reach exponential phase and stress response experiment in the presence of 2 g/L furfural from the beginning of fermentation were carried out to study the short and long-term effect of furfural on 8b physiological and transcriptional profiles. The presence and supplementation of furfural negatively affect 8b growth in terms of final biomass and the fermentation time. Transcriptomic studies indicated that the response of 8b to furfural is dynamic, complex and differences exist between short-term shock response and long-term stress response. However, the gene function categories are similar with most downregulated genes related to translation and biosynthesis, while the furfural-upregulated genes were mostly related to cellular processes of general stress response and energy metabolism. Conclusions: Similar to previous report that acetate inhibited the growth of Z. mobilis 8b in RM using glucose or xylose as carbon source, the existence or supplementation of another major hydrolysate inhibitor furfural also inhibited 8b growth with slowing the substrate utilization and ethanol production. The difference between carbon sources is more dramatic than that of the major hydrolysate inhibitors of both NH4OAc (GSE57553) and furfural (this study). Several gene targets have been selected for genetic studies with promising preliminary results.

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Preparation of Furfural From Xylose Catalyzed by Diimidazole Hexafluorophosphate in Microwave.

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