Ketone Products Research Articles

High-performance benzyl alcohol oxidation catalyst: Au-Pd alloy with ZrO2 as promoter

Achieving the balance between the catalytic activity and product selectivity still remains a challenge in partial oxidation processes, because the products are prone to be over-oxidized. Lewis acids (such as AlCl3) have previously been identified to interact with CO groups, which can prevent the ketone products from further transformation. In this work, ZrO2 promoted Au-Pd/γ-Al2O3 catalyst was designed to enhance the benzaldehyde selectivity by generating more surface Lewis acid site on ZrO2-modified alumina. Results show that the introduction of ZrO2 (5%) resulted in the formation of more surface Lewis acid sites, which improved the benzaldehyde selectivity through the strengthened interaction between the Lewis acid sites and CO groups in benzaldehyde. Besides, the addition of small amount of ZrO2 enhanced the noble metal dispersion and led to the formation of more active sites to improve the oxygen transfer during the reaction.

Streamlined Catalytic Enantioselective Synthesis of α-Substituted β,γ-Unsaturated Ketones and Either of the Corresponding Tertiary Homoallylic Alcohol Diastereomers.

A widely applicable, practical, and scalable strategy for efficient and enantioselective synthesis of β,γ-unsaturated ketones that contain an α-stereogenic center is disclosed. Accordingly, aryl, heteroaryl, alkynyl, alkenyl, allyl, or alkyl ketones that contain an α-stereogenic carbon with an alkyl, an aryl, a benzyloxy, or a siloxy moiety can be generated from readily available starting materials and by the use of commercially available chiral ligands in 52-96% yield and 93:7 to >99:1 enantiomeric ratio. To develop the new method, conditions were identified so that high enantioselectivity would be attained and the resulting α-substituted NH-ketimines, wherein there is strong C═N → B(pin) coordination, would not epimerize before conversion to the derived ketone by hydrolysis. It is demonstrated that the ketone products can be converted to an assortment of homoallylic tertiary alcohols in 70-96% yield and 92:8 to >98:2 dr-in either diastereomeric form-by reactions with alkyl-, aryl-, heteroaryl-, allyl-, vinyl-, alkynyl-, or propargyl-metal reagents. The utility of the approach is highlighted through transformations that furnish other desirable derivatives and a concise synthesis route affording more than a gram of a major fragment of anti-HIV agents rubriflordilactones A and B and a specific stereoisomeric analogue.

Synthesis of Aromatic Polyether Ketones by Electrophilic Substitution

This article presents a scientific review of the literature on the production of polyether ketones and copolymers of various structures with a complex of valuable properties. Particular attention is paid to the synthesis of polyether ketones by electrophilic substitution by the Friedel-Crafts reaction mechanism.

Ruthenium-Catalyzed α-Alkylation of Ketones Using Secondary Alcohols to β-Disubstituted Ketones.

An assortment of aromatic ketones was successfully functionalized with a variety of unactivated secondary alcohols that serve as alkylating agents, providing β-disubstituted ketone products in good to excellent yields. Remarkably, challenging substrates such as simple acetophenone derivatives are effectively alkylated under this ruthenium catalysis. The substituted cyclohexanol compounds displayed product-induced diastereoselectivity. Mechanistic studies indicate the involvement of the hydrogen-borrowing pathway in these alkylation reactions. Notably, this selective and catalytic C-C bond-forming reaction requires only a minimal load of catalyst and base and produces H2O as the only byproduct, making this protocol attractive and environmentally benign.

Primary amine coupling on nanocarbon catalysts: Reaction mechanism and kinetics via fluorescence probe analysis

Non-metallic nanocarbon materials catalyzed coupling reactions of primary amines to produce imine is an efficient, green and sustainable synthetic route, which has a wide application prospect in fine chemicals or pharmaceutical molecules. In the present study, we show firstly the relatively high catalytic activity of graphene oxide in the reaction of oxidative coupling of benzylamine (OCB), which is even comparable with typical metal-based catalysts, indicating the great potential of nanocarbon materials in this reaction system. More importantly, a novel two-photon fluorescence probe molecule (N-propyl-4-hydrazinyl-1, 8-naphthalimide, NA) with special chemical structure of hydrazine functionality was synthesized. The probe NA could selectively react with aldehyde or ketone compounds, leading to the photoluminescence enhancement via inhibition of photo induced electron transfer (PET) process. The synthesized NA was applied as probe in carbon catalyzed OCB system to predict the existence of reaction intermediate benzaldehyde (BA), indicating the reaction pathway of oxidation-deamination-condensation in nanocarbon catalyzed OCB process. The proposed luminescence-probe strategy for revealing the kinetics and mechanism may also shed light in other reaction systems concerning the intermediates or products of ketones or aldehydes.

Manipulation of thick‐walled PEEK bushing crystallinity and modulus via instrumented compression molding

AbstractAn instrumented hot compression molding apparatus was fabricated to allow real‐time monitoring and precise temperature control during the compaction and consolidation of large polyether ether ketone (PEEK) products. The objective was to determine the impact of controlled variables on the properties of the molded article. Four different strategies were designed to control the mold thermal profiles. The average crystallinity in a commercial molding process is restricted due to large thermal masses with low thermal conductivity. In contrast, this research was able to reduce the crystallinity range from 33% to 6% by developing a special controlled apparatus and implementing new processing methodologies. In this study, PEEK showed a significant increase in the modulus compared to typical values measured on commercially produced analogs, and a higher degree of property uniformity. In a single commercially molded PEEK billet, compressive modulus variability was 13% at room temperature, and 21% at 225°C. Properties of billets produced using the laboratory apparatus showed a reduction in variability to 2%.

Ketonization of xylose over CeO2 to produce mono-functional ketones

Ketonization of biomass-derived oxygenates provides an efficient way for bio-oil upgrading. However, little information on the ketonization of oxygen-rich sugars has been reported, leaving the deep deoxygenation of biomass an unsolved challenge. To address the problem, this paper investigated the catalytic pyrolysis of xylose over nano-CeO2 using an analytical pyrolyzer. Results showed that upon the addition of CeO2, multi-functional oxygenated compounds from xylose pyrolysis were majorly reformed to mono-functional ketonic products, resulting in a 5-fold increase in peak area of ketones. Among them, acetone and 2-butanone presented the highest selectivity of 51% with the CeO2 to xylose ratio of 10:1 at the temperature of 600 °C. Meanwhile, the short-chain oxygenates, i.e. C2-C3 aldehydes and alcohols, had been converted into C3-C5 ketones, indicating an outstanding ability of chain-increasing over CeO2. Both the catalyst dosage and the pyrolysis temperature play a vital role during the ketonization process. The reaction mechanism was proposed according to the experimental results, in which three major reaction pathways were analyzed. This study demonstrates that ketonization of biomass-derived sugars is a promising method for oxygen removal and carbon chain increase, thus improving the bio-oil quality.

Monitoring of Energy Metabolism by Organic Acid Profiling Analysis in Plasma of Type 2 Diabetic Mice

Objective:: This study was conducted to investigate energy metabolism based on changes in organic acids in diabetes and to establish a correlation between metabolites or bone microarchitecture and the glucose index in type 2 diabetic mice. Method:: Seven-week-old male C57BL/6 mice were randomly divided into a non-diabetic group and a diabetic group. The diabetic group was fed a high-fat diet (HFD) that induced insulin resistance for 5 weeks. Afterwards, diabetes was induced by a single streptozotocin injection. Both the groups were fed a normal diet and HFD diet for 9 weeks. Results:: The fasting blood glucose level glycosylated hemoglobin (HbA1c) significantly increased in diabetic mice. Bone-alkaline phosphatase activity decreased in the diabetic group. Diabetes increased the levels of ketone bodies, including 3-hydroxybutyric, acetoacetic and butyric acid, whereas it decreased Krebs cycle components, including succinic acid and malic acid, as well as levels of glycolytic products, including lactic acid. Diabetes also induced a shortage of trabecular bone mineral density (BMD) by the regulation of trabecular morphometric parameters in the femur and tibia. Correlation analysis indicated that BMD, Krebs cycle components and lactic acid levels were negatively correlated with HbA1c, whereas ketone bodies were positively correlated with HbA1c. Conclusion: : This research suggested that uncontrolled HbA1c can affect bone loss, production of ketone bodies and utilization of glucose metabolites for energy production in type 2 diabetes.

Selective aerobic oxidation of allyl phenyl ether to methyl ketone by palladium–polyoxometalate hybrid catalysts

In this study, we report that selective aerobic oxidation of allyl phenyl ethers is attained by a Pd catalyst/polyoxometalate hybrid system to yield corresponding methyl ketones in water-enriched acetonitrile. The Pd(OAc)2/H5PV2Mo10O40 system exhibits higher conversions and yields of corresponding methyl ketone by Wacker-type oxidation of allyl phenyl ether as compared with the conventional PdCl2/CuCl2 system. The higher yields are attributed to the efficient re-oxidation of Pd0 to Pd2+ by H5PV2Mo10O40 using O2 as an oxidant as evidenced by electrochemical measurements. A reduced species of H5PV2Mo10O40 by Pd0 during the catalytic oxidation is revealed by UV–vis spectral measurements. The use of PdCl2 in place of Pd(OAc)2 in combination with [PV2Mo10O40]5− bearing tetraalkylammonium counter cations has also exhibited comparable conversions and product yields in the Wacker-type oxidation of allyl phenyl ethers. Para-substituted allyl phenyl ether derivatives are successfully oxidized in the Pd catalyst/polyoxometalate system to yield corresponding methyl ketones. The initial rate of products of para-substituted methyl ketones depended on the electronic effect of the substituents in which allyl phenyl ethers with electron-donating groups have accelerated the initial rate in the Pd catalyst/polyoxometalate system.

Mechanism and Origin of Chemoselectivity of Ru-Catalyzed Cross-Coupling of Secondary Alcohols to β-Disubstituted Ketones.

Ru-catalyzed cross-coupling of secondary alcohols with only byproducts H2 and H2O provides a green synthetic strategy to prepare β-disubstituted ketones. Density functional theory (DFT) calculations were performed with the coupling of 1-phenylethanol and cyclohexanol as a model reaction to gain deeper mechanistic insights herein. The mechanistic details of the main reaction and the key steps of possible side reactions were clarified, and the obtained results are consistent with reported selectivity. Hydrogenation of α,β-unsaturated ketones and dehydrogenation of ruthenium hydride intermediate are direct chemoselectivity-determining stages. The hydrogenation via 1,4-addition generates more stable intermediates, being favored over that via 1,2-addition, and thus avoids the formation of alkene products. The conjugation and π-π stacking effects of phenyl and the weak electronic effect of alkyls explain the dominance of specific ketone products in the hydrogenation stage. Hydrogenation of ketone products is kinetically operative but not exergonic enough to stop the irreversible dihydrogen release in an open reaction system, and thus alcohol products are absent. Furthermore, water evaporation in aldol condensation is found to be a double-edged sword, as it can accelerate the hydrogenation stage to prevent α,β-unsaturated ketones from being the main products but decrease the selectivity therein from thermodynamics overall.

Effects of Propylene Glycol on Negative Energy Balance of Postpartum Dairy Cows.

Simple SummaryAfter calving, the milk production of dairy cows increases rapidly, but the nutrient intake cannot meet the demand for milk production, forming a negative energy balance. Dairy cows in a negative energy balance have an increased risk of developing clinical or subclinical ketosis. The ketosis in dairy cows has a negative impact on milk production, dry matter intake, health, immunity, and reproductive performance. Propylene glycol can be used as an important gluconeogenesis in ruminants and can effectively inhibit the formation of ketones. Supplementary propylene glycol to dairy cows during perinatal is an effective method to alleviate the negative energy balance. This review summarizes the reasons and consequences of negative energy balance as well as the mechanism and effects of propylene glycol in inhibiting a negative energy balance in dairy cows. In addition, the feeding levels and methods of using propylene glycol to alleviate negative energy balance are also discussed.With the improvement in the intense genetic selection of dairy cows, advanced management strategies, and improved feed quality and disease control, milk production level has been greatly improved. However, the negative energy balance (NEB) is increasingly serious at the postpartum stage because the intake of nutrients cannot meet the demand of quickly improved milk production. The NEB leads to a large amount of body fat mobilization and consequently the elevated production of ketones, which causes metabolic diseases such as ketosis and fatty liver. The high milk production of dairy cows in early lactation aggravates NEB. The metabolic diseases lead to metabolic disorders, a decrease in reproductive performance, and lactation performance decline, seriously affecting the health and production of cows. Propylene glycol (PG) can alleviate NEB through gluconeogenesis and inhibit the synthesis of ketone bodies. In addition, PG improves milk yield, reproduction, and immune performance by improving plasma glucose and liver function in ketosis cows, and reduces milk fat percentage. However, a large dose of PG (above 500 g/d) has toxic and side effects in cows. The feeding method used was an oral drench. The combination of PG with some other additives can improve the effects in preventing ketosis. Overall, the present review summarizes the recent research progress in the impacts of NEB in dairy cows and the properties of PG in alleviating NEB and reducing the risk of ketosis.

High titer methyl ketone production with tailored Pseudomonas taiwanensis VLB120

High titer methyl ketone production with tailored <i>Pseudomonas taiwanensis</i> VLB120

Pretreatment with saturated and unsaturated fatty acids regulates fatty acid oxidation in Madin-Darby bovine kidney cells

Metabolic fates of fatty acids in tissue may be influenced by extracellular concentration and profile of fatty acids. Previous work has demonstrated the ability of C18:3n-3 cis to ameliorate the effects of C16:0- or C18:0-induced depression of pyruvate carboxylase (PC) mRNA expression. Pyruvate carboxylase catalyzes oxaloacetate synthesis and connects gluconeogenesis from lactate and fatty acid metabolism. Our objective was to determine the effects of co-presence of saturated and unsaturated fatty acids on cellular partitioning of [1-14C]C16:0 metabolism to CO2 or acid-soluble products (ASP) in Madin-Darby bovine kidney cells and the role of PC in this relationship. We hypothesized that the ratio of saturated to unsaturated fatty acid pretreatments regulates [1-14C]C16:0 partitioning to CO2 or ASP. Cells were exposed for 21 h to either individual fatty acids, C16:0, C18:0, C18:1n-9 cis, or C18:3n-3 cis, or to fatty acid combinations in 10:90, 25:75, 50:50, 75:25, or 90:10 ratios for 3 combinations: C16:0/C18:3n-3 cis, C18:0/C18:3n-3 cis, or C18:1n-9 cis/C18:3n-3 cis. Total fatty acid concentration was 1.0 mM during the 21-h pretreatment phase. Following the 21-h incubation phase with fatty acid combinations, cells were incubated in the presence of 1.0 mM [1-14C]C16:0 for 3 h to determine the rate of metabolism to CO2 and ASP collection (per µg DNA-1·h-1). Pretreatment with either C16:0 or C18:0 alone significantly depressed subsequent oxidation of [1-14C]C16:0 to ASP by 62.7 and 41.2%, respectively, compared with C18:3n-3 cis pretreatment. Similar patterns were observed for [1-14C]C16:0 oxidation to CO2. Expression of PC mRNA was significantly decreased with exposure to either C16:0 or C18:0 compared with expression after exposure to either C18:3n-3 cis or control 1% BSA in Dulbecco's modified Eagle's medium. Expression of cytosolic phosphoenolpyruvate carboxykinase (PCK1) mRNA followed a similar pattern. Fatty acid treatments containing C18:1n-9 cis did not alter PC or PCK1 expression from control or C18:3n-3 cis results. Pearson coefficient correlations were determined for PC mRNA expression and rate of [1-14C]C16:0 metabolism to CO2 or ASP, including ketones, and for PCK1 mRNA expression and rate of [1-14C]C16:0 metabolism to CO2 or ASP. Production of CO2 from [1-14C]C16:0 was positively correlated (r = 0.63) with PC expression, whereas ASP production from [1-14C]C16:0 only tended to positively correlate (r = 0.51) with PC mRNA expression. Production of CO2 or ASP from [1-14C]C16:0 were both positively correlated (r = 0.80 and r = 0.69, respectively) with PCK1 expression. Results show a regulation of ketone production by Madin-Darby bovine kidney cells in response to saturated and unsaturated fatty acid pretreatments.

High titer methyl ketone production with tailored Pseudomonas taiwanensis VLB120

Methyl ketones present a group of highly reduced platform chemicals industrially produced from petroleum-derived hydrocarbons. They find applications in the fragrance, flavor, pharmacological, and agrochemical industries, and are further discussed as biodiesel blends. In recent years, intense research has been carried out to achieve sustainable production of these molecules by re-arranging the fatty acid metabolism of various microbes. One challenge in the development of a highly productive microbe is the high demand for reducing power. Here, we engineered Pseudomonas taiwanensis VLB120 for methyl ketone production as this microbe has been shown to sustain exceptionally high NAD(P)H regeneration rates. The implementation of published strategies resulted in 2.1 g Laq−1 methyl ketones in fed-batch fermentation. We further increased the production by eliminating competing reactions suggested by metabolic analyses. These efforts resulted in the production of 9.8 g Laq−1 methyl ketones (corresponding to 69.3 g Lorg−1 in the in situ extraction phase) at 53% of the maximum theoretical yield. This represents a 4-fold improvement in product titer compared to the initial production strain and the highest titer of recombinantly produced methyl ketones reported to date. Accordingly, this study underlines the high potential of P. taiwanensis VLB120 to produce methyl ketones and emphasizes model-driven metabolic engineering to rationalize and accelerate strain optimization efforts.

Oxidative dehydrogenation of ethanol on gold: Combination of kinetic experiments and computation approach to unravel the reaction mechanism

Selective alcohol dehydrogenation on heterogeneous catalysts is a key industrial reaction for production of aldehydes, ketones, and carboxylic compounds. Design of catalysts with improved activity and selectivity requires understanding of the reaction mechanism and kinetics. Herein, experiments, density functional theory (DFT) and kinetic modelling were combined to elucidate the mechanism and kinetics of ethanol oxidative dehydrogenation to acetaldehyde on gold catalysts. Catalytic experiments clearly emphasized the role of oxygen in this reaction. Ethanol conversion was rather independent on the gold cluster size. Formation of minor products, acetic acid and ethyl acetate was structure sensitive as on smaller clusters ethanol is less prone to oxidation reacting more efficiently with acetic acid to ethyl acetate. DFT calculations indicated that the activation of molecular oxygen is facilitated by the hydrogen bond donor e.g., ethanol, leading to hydrogen abstraction from the bond donor and formation of an OOH intermediate followed by its facile dissociation. Furthermore, the calculations show that ethanol oxidation along such pathway is thermodynamically feasible on smooth Au(111) facets. The kinetic model developed based on the concept of ethanol mediated activation of oxygen derived from DFT studies, qualitatively and quantitatively by data fitting reproduces experimental observations on ethanol oxidative dehydrogenation over gold on alumina catalyst. The concentration profiles in the catalyst particle were calculated numerically to evaluate the role of diffusion in the catalyst pores. Combining experiments and DFT with kinetic modelling provides a powerful way to unravel the mechanisms and kinetics of heterogeneous catalytic reactions.

Mechanical Insights into the Enzymatic Cleavage of Double C-C Bond in Poly(cis-1,4-isoprene) by the Latex Clearing Protein.

The b-type cytochrome LcpK30 is a latex clearing protein (Lcp), which acts as an endotype dioxygenase to catalyze the extracellular cleavage of the chemically inert aliphatic polymer poly(cis-1,4-isoprene), producing oligo-isoprenoids with different terminal carbonyl groups (aldehyde and ketone, -CH2-CHO and -CH2-COCH3). On the basis of the fact that the muteins of E148A, E148Q, and E148H have substantially reduced reactivity, and the E148-initiated reaction mechanism has been previously proposed, in which a cyclic dioxetane intermediate or an epoxide intermediate may be involved, however, open questions still remain. In this paper, on the basis of the crystal structure of LcpK30, the enzyme-substrate reactant model was constructed, and the cleavage mechanism of the central double bond of poly(cis-1,4-isoprene) was elucidated by performing quantum mechanics/molecular mechanics calculations. Our calculation results revealed that the oxidative cleavage reaction is triggered by the addition of the heme-bound dioxygen to the double bond of the polymer, and E148 does not act as the catalytic base to extract the allylic proton to assist the reaction as previously suggested. Of the two considered pathways, the pathway that involves the dioxetane intermediate was calculated to be more favorable. During the catalysis, the distal oxygen first adds to the double bond of the substrate to form a radical intermediate, and then the Fe-O1 (proximal oxygen) bond cleaves to generate the dioxetane intermediate, which can easily collapse affording the final ketone and aldehyde products. In general, the cleavage mechanism of double C-C bond catalyzed by LcpK30 is similar to those of indoleamine 2,3-dioxygenase, tryptophan 2,3-dioxygenase, and the nonheme stilbene cleavage oxygenase NOV1 that all depend on the iron-bound dioxygen to initiate the cleavage reaction.

Loss of HMGCS2 Enhances Lipogenesis and Attenuates the Protective Effect of the Ketogenic Diet in Liver Cancer.

Hepatocellular carcinoma (HCC) is the most common primary malignant liver tumor with limited treatment. The ketogenic diet (KD) emerged as a metabolic therapy for cancer; however, the antitumor effect on HCC remains controversial. We previously reported that the ketogenesis rate-limiting enzyme, 3-hydroxymethylglutaryl-CoA synthase 2 (HMGCS2), was downregulated in most patients with HCC. The knockdown of HMGCS2 enhanced the proliferation and metastasis ability of HCC cells. However, the role of HMGCS2 in affecting KD-mediated metabolic effects remains unclear. Here, we report that KD feeding upregulates HMGCS2 expression and inhibits HCC tumor growth, while a reverse correlation between tumor size and HMGCS2 expression was observed. We found that HCC cells with HMGCS2 downregulation possess altered lipid metabolism that increases fatty acid, triglyceride, and cholesterol synthesis. Under KD feeding, a higher tumor growth rate was observed in HMGCS2 knockdown tumors, which had increased lipid synthesis-related marker expression and a positive correlation between lipid quantity and tumor weight. In conclusion, these results demonstrate that the downregulation of HMGCS2 attenuates the protective effect of the KD by shifting ketone production to enhance de novo lipogenesis in HCC. Our study elucidates a new molecular mechanism underlying the crosstalk between HMGCS2 expression and the KD in cancer treatment, which provides more information for precision medicine in developing personalized treatment strategies.

Unique Medium Chain Triglyceride Product Rapidly Enhances Brain Function: A Pilot Investigational Study

PURPOSE: Medium Chain Triglyceride (MCT) compounds are purported to increase brain energy based upon the relationship between MCT products and ketone production, especially for older individuals or those on low-carbohydrate diets. Little evidence exists that MCT products positively affect brain function, short-term. In this pilot study, Intervention Group (IG )subjects were tested prior to ingestion of a proprietary MCT product, and then 90 minutes later using the same electro-encephalographic (EEG) device and compared to a control group (CG). METHODS: Eight (8) IG volunteers, aged 49-68 years old, (male = 5, female =3) were compared to three (3) CG volunteers, aged 48 to 68 years old, (male = 3). Study subjects completed standard EEG testing prior to ingestion of the compound, and 90 minutes after consuming the compound or placebo. Testing consisted of a P300 audio reaction time test and two visual decision making/reaction tests. RESULTS: The IG increased brain function as measured with evoke potentials, time to task and graphic representations compared to the control group. The decrease for the IG in the audio reaction time test was 340 milliseconds to 314 milliseconds. In addition, the tens of millivolt (μV) activation during the auditory reaction time test increased from 7.5 μV to 12.9 μV, indicating increased brain functional activity. The CG showed essentially no voltage changes. The IG decreased times in the first trail making test from 94 to 57 seconds, and decreased time to complete the second trail making test from 113 to 93 seconds. Descriptive statistics revealed the measures for the IG had statistical significance (P<0.5) for the second trail making test and strong positive trends for all other parameters. Topographic brain maps from the test revealed a representative picture of the changes from taking the supplement. CONCLUSIONS: In this pilot study, consumption of a proprietary MCT combination produced marked enhancement in brain activity 90 minutes after ingestion with significant increases in relation to topographical brain maps. Further investigation is warranted to determine optimal ingestion conditions and time to effect for this and similar products across various populations. EEG measurements show promise as assessment biomarkers for the effects of nutritional supplements on brain function.

Contribution of autochthonous yeasts with probiotic potential to the aroma profile of fermented Guajillo pepper sauce.

Three yeast strains with probiotic potential, Hanseniaspora opuntiae, Pichia kudriavzevii, and Wickerhamomyces anomalus were inoculated in the fermentation of Guajillo chilli pepper (Capsicum annuum L.) sauce, and the different aroma profiles were investigated. Using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis and gas chromatography-olfactometry (GCO), flavour compound production was evaluated during the fermentation of the Guajillo chilli pepper sauces. A total of 78 volatile compounds were identified during the yeast fermentation of the sauce. Most aldehydes and terpenes detected were present at the beginning of the fermentation, indicating a Guajillo chilli pepper origin. Among the 34 active aroma compounds detected by GCO, propanoic acid (cheesy), 3-methylbutanoic acid (sharp, cheese), ethyl 2-methylbutanoate (fruity), and 6-methyl-5-hepten-2-one (strong, citrus) were identified as key aroma contributors produced by the inoculation of the yeasts. A different aroma profile was produced by probiotic yeast. Hanseniaspora opuntiae produced an aroma profile with herbal and green notes based on high production of aldehydes, ketones, and acetic acid. Pichia kudriavzevii and W. anomalus produced fruity, green-herbal, and cheesy notes based on ester compounds, alcohol and branched-chain acids production although, the production of propanoic acid by W. anomalus increased the cheesy character in the sauces. The aroma profile of fermented chilli pepper sauces depends not only on the chili pepper varieties used but also on the fermentation process as a source of aroma compounds. The use of probiotic yeast can be used to improve and diversify the aroma profile of fermented chilli pepper sauces. © 2020 Society of Chemical Industry.

Biofuels and renewable chemicals production by catalytic pyrolysis of cellulose: a review

The rise of consumption of traditional fossil fuels has caused emissions of greenhouse gas and deterioration of air quality. Biomass is a promising substitute for fossil fuels because biomass provides biofuels and chemicals by thermochemical conversion such as pyrolysis. In particular, fast pyrolysis of biomass cellulose into chemicals and biofuels has recently drawn attention. Issues of commercialization of fast pyrolysis products include low heating value, low stability, and high oxygen content and acidity. Consequently, new catalysts for enhanced cellulose conversion are sought for. Here, we review the production of biofuel and renewable chemicals from cellulose pyrolysis using acidic and basic catalysts. Acidic catalysts are more suitable to produce biofuels containing about 50% aromatic hydrocarbons, compared to basic catalysts which give biofuels containing 15% aromatic hydrocarbons. Basic catalysts are preferred to produce renewables chemicals, particularly ketone compounds. We explain the mechanism of cellulose pyrolysis with acidic and basic catalysts. The strong acid sites on the catalyst facilitate high selectivity for aromatic compounds in the pyrolysis oil, whereas basic active sites induce double-bond migration, increase carbon-coupling reactions, and ketone production.