Production Of Aromatic Compounds Research Articles

Synergistic regulation of dual thresholds: Hydroxyl occupancy and carbon species in the targeted catalytic hydrocracking of lignite

The preparation of carbon-based catalyst supports from low-grade lignite, followed by its self-catalytic hydrocracking to produce lignite-derived aromatic compounds, is crucial for achieving efficient lignite utilization and expanding aromatic compound sources. During lignite catalytic hydrocracking, the uncontrolled diffusive migration of active hydrogen (H*) and insufficient protection of aromatic rings reduce the yield of aromatic compounds. Using Heishan lignite as the raw material, we employed a relay process of thermal-induced self-assembly and oxidation-mediated carbon distortion for fabricating the Co3O4/AC&GC-S-600 composite material, which features an optimal hydroxyl occupancy ratio and a balanced combination of amorphous carbon/graphite carbon (AC/GC) types. The optimal hydroxyl occupancy threshold balances Co3O4 dispersion and hydrophilicity, facilitating the efficient formation and directional migration of H* through synergistic interaction between Co3O4 and H2O. The adequate threshold of AC/GC ratio regulates substrate adsorption, activation, and inhibition of aromatic hydrogenation, enhancing selective C–O bridge bond cleavage and preserving the unsaturation of aromatic rings. The synergistic regulation of dual thresholds promotes the rapid formation and the directional migration of H*, enabling efficient conversion of Heishan lignite to aromatic compounds (45.8% conversion, 80.8% selectivity) under mild conditions. Characterization techniques, experimental analyses, kinetic studies, and density functional theory calculations confirm that thermally induced self-assembly and oxidation-mediated carbon distortion are crucial for redistributing the carbon framework of the Heishan lignite matrix and regulating the optimal dual thresholds of hydroxyl occupancy and AC/GC types, which are essential for the catalytic hydrocracking of Heishan lignite to aromatic compounds. This strategy provides a scientific basis for selective catalytic production of lignite-based aromatic compounds, thereby supporting its clean and efficient utilization.

Filamentous fungi as emerging cell factories for the production of aromatic compounds.

Microbial production of aromatic compounds from renewable feedstocks has gained increasing interest as a means towards sustainable production of chemicals. The potential of filamentous fungi for production of aromatic compounds has nonetheless not yet been widely exploited. Notably, many filamentous fungi can naturally break down lignin and metabolize lignin-derived aromatic compounds. A few examples where a fungal cell factory, often of Aspergillus spp., is used to produce an aromatic compound, typically through the conversion of one compound to another, have already been reported. In this review, we summarize fungal biosynthesis of biotechnologically interesting aromatic compounds. The focus is on compounds produced from the shikimate pathway. Biorefinery-relevant efforts for valorizing residual biomass or lignin derived compounds are also discussed. The advancement in engineering tools combined with the increasing amounts of data supporting the discovery of new enzymes and development of new bioprocesses has led to an increased range of potential production hosts and products. This is expected to translate into a wider utilization of fungal cell factories for production of aromatic compounds.

Effects of Nitrogen Concentration in Nutrient Solution on Growth, Yield and Phytochemical and Aromatic Compounds of Persicaria minor Cultivated Using Hydroponics System

Persicaria minor, locally known as kesum and belonging to the family Polygonaceae, is a widely used aromatic herb in Malaysia. Cultivating kesum hydroponically using a deep-water culture (DWC) system presents an alternative method for growers to enhance crop yields. This system delivers a liquid fertilizer solution directly to the plant roots, eliminating the need for a growth medium or water flow. Kesum contains phytochemical compounds such as quercetin-3-glucuronide and quercitrin, which have medicinal properties. The primary objective of this study was to assess the effects of nitrogen concentration on the growth, yield, phytochemical (quercetin-3-glucuronide and quercitrin) and aromatic (aldehyde and caryophyllene) content of kesum cultivated in a hydroponic system. Plants were grown under four nitrogen concentration regimes: 200 mg/L, 100 mg/L, 50 mg/L, and 0 mg/L. The experiment was conducted under a side-netted rain shelter and arranged in a Randomized Complete Block Design (RCBD) with four replications. The plants were harvested eight weeks after planting. The result indicted those supplemented with 100 mg/L of nitrogen exhibited the best growth performance and biomass yield, along with the highest levels of aromatic compounds (aldehyde C-10: 5.80% and aldehyde C-12: 12.23%). Plants treated with 50 mg/L of nitrogen produced the highest amounts of quercetin-3-glucuronide (98.261 µg/mL) and quercitrin (61.367 µg/mL) compared to other treatments. Additionally, plants receiving 200 mg/L of nitrogen had the highest caryophyllene content (12.53%). In conclusion, the deep-water culture system in hydroponics can effectively cultivate kesum, allowing for adjustments in nitrogen concentration to achieve optimal yields, phytochemical levels, or aromatic compound production based on specific objectives.

Bifunctional Catalytic Performance of Zn/ZSM-5 in the Aromatization of LPG and the Conversion of Pyrolytic Gases from Recycled Polypropylene

Zn-modified ZSM-5 zeolites with different zinc contents were successfully prepared by the impregnation method and compared with unmodified ZSM-5. Their potential for LPG (liquefied petroleum gas) aromatization and the conversion of pyrolysis gases obtained from recycled polypropylene was subsequently evaluated. In this process, various characterization tests were performed on the prepared catalysts, including SEM-EDS (scanning electron microscopy with energy-dispersive spectroscopy), TPD-NH₃ (temperature-programmed desorption of ammonia), and FTIR (Fourier-transform infrared spectroscopy). Under optimized conditions, the best results were obtained with 2% Zn/ZSM-5, which generated a higher production of BTX (benzene, toluene, and xylene) isomers, which are major components of gasoline. Likewise, in catalytic pyrolysis of recycled polypropylene, this catalyst generated a higher production of aromatic compounds. Therefore, this catalyst showed excellent performance in generating valuable hydrocarbons of great industrial interest, particularly aromatics.

Combined analysis of transcriptome and metabolome reveals the effects of novel aroma-producing Naumovozyma castellii on Feng-flavor Baijiu

Feng-flavor Baijiu has an elegant and pleasant aroma and is one of the four traditional famous liquors in China. A strain of Naumovozyma castellii XF0241 with excellent fermentation performance and rich aroma compounds was isolated and screened from the Feng-flavor fermented grains. Metabolomic analysis showed that the main flavor compounds of XF0241 are esters, terpenes, and heterocyclic compounds, which are important aroma and flavor compounds in Feng-flavor Baijiu. Compared with the model strain N. castellii CBS4309, the yeast's ester, terpenes and heterocyclic compounds were up-regulated by 168.99 ± 45.31 %, 103.54 ± 28.45% and 108.46 ± 36.78% respectively. After adding additional XF0241 to the Feng-flavor fermented grains, the flavor compounds became more abundant, among which the ester showed the highest increase, followed by terpenoids and heterocyclic compounds. Transcriptomic analysis showed that 1134 genes were differentially expressed. The combined analysis of transcriptome and metabolome revealed that 10 enzymes related to ester production and 3 enzymes related to terpenoid biosynthesis, and 1 enzyme related to heterocyclic formation were significantly upregulated. We believe that XF0241 is one of the core yeasts of Feng-flavor Baijiu. Its production of rich aroma compounds plays an important role in the formation of the special aroma of liquor.

Alkaline treatment for targeted lignin breakdown in rice straw: Maximizing phenolic content and product characterization

Lignin is a significant renewable source for the production of phenolics and aromatic compounds for use as functional materials. Rice straw (RS), a lignocellulosic biomass was given alkaline treatment, to breakdown lignin into methoxyphenols and heterocyclic compounds, leaving behind carbohydrate rich residue. Process parameters such as NaOH (M), time (min) and liquid to solid (L:S) ratio (mL/g) were optimized using Response Surface Methodology (RSM) to enhance the extraction of phenolics. The maximum phenolic content (13.98 mg/g RS) was obtained after treatment with 3 M NaOH for 30 min with L: S ratio of 20:1 mL/g at 121°C. GC-MS revealed the presence of 14 compounds, primarily methoxyphenols like acetosyringone (32.44 %), 2-methoxy-4-vinyl phenol (23.71 %), vanillin (1.25 %) and 2, 6-dimethoxyphenol (1.49 %). Additionally, a significant proportion of a heterocyclic compound, 2, 3-dihydrobenzofuran (31.72 %), was also present. The extract exhibited considerable levels of 2, 2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC50 (half-maximal inhibitory concentration) = 0.45 mg/mL) radical scavenging activity, which was comparable to ascorbic and gallic acids. With substantial conversion (60.17 %) of rice straw lignin to phenols and simultaneous recovery of both cellulose (45.7 %) and hemicellulose (14.6 %), this process can be useful in biorefining of lignocellulosic biomass to phenolic chemicals for application in food and pharmaceutical industry.

Molecular cloning, expression, and biochemical characterization of carotenoid cleavage dioxygenase 1 (LbCCD1) from Lycium barbarum

Carotenoid cleavage dioxygenases (CCDs) play a pivotal role in the biosynthesis of volatile apocarotenoids, which have significant industrial applications due to their aromatic and bioactive properties. This study focuses on the molecular cloning and biochemical characterization of the LbCCD1 from Lycium barbarum. The LbCCD1 gene was successfully cloned and heterologously expressed in Escherichia coli and several carotenoids were using as substrates for investigate its specificity by in vitro and in vivo experiment. The LbCCD1 protein was able to cleave a variety of carotenoids including β-carotene, zeaxanthin, astaxanthin, and β-apo-8′-carotenal, at the 9, 10 (9′, 10′) double bond to produce β-ionone, 3‑hydroxy-4-oxo-β-ionone, and 3‑hydroxy-β-ionone, respectively in vitro. LbCCD1 could also cleave zeaxanthin and β-carotene at the 9, 10 (9′, 10′) double bond to produce β-ionone, respectively, in E. coli accumulating carotenoids. Interestingly, LbCCD1 did not exhibit cleavage activity on lycopene either in vivo or in vitro unlike other CCD1 family enzymes.In the previous experiment, it was confirmed that LbCCD1 exhibits cleavage activity towards β-apo-8′-carotenal in vitro, so we used β-apo-8′-carotenal as the substrate for characterizing the enzymatic properties. The expression of LbCCD1 was optimized at such conditions (temperature 24 °C, IPTG 0.1 mM, induction time 24 h). The biochemical characterization of LbCCD1 revealed the optimal activities were at pH 9 and 55 °C. The addition of 10 % ethanol could increase enzyme activity to above 15 %. However, the concentration of Fe2+ has a minimal effect on enzyme activity. The Vmax for β-apo-8′-carotenal was 8.6 U/mg, while the Km was 0.27 mM. To preliminarily verify the potential of LbCCD1 as a biological component for β-ionone production. By introducing LbCCD1 into the β-carotene-high-producing chassis cell and optimizing the conditions (temperature 30 °C, IPTG 0.01 mM, Fe2+ concentration 0.05 mM), the β-ionone yield reached 21.45 mg/L. This study focused on one of the CCDs derived from woody plants, which have been relatively underexplored. It lays the groundwork for expanding the CCD enzyme library, identifying suitable CCDs, and investigating the structure-function relationship of CCDs. Furthermore, it sets the stage for engineering novel CCD genes and developing advanced applications of CCDs as biocatalysts and platforms for synthetic biology. These advancements will enable the efficient production of volatile aroma compounds from carotenoids.

Optimizing the fermentation parameters in the Lactic Acid Fermentation of Legume-based Beverages– a statistically based fermentation

BackgroundThe market for beverages is highly changing within the last years. Increasing consumer awareness towards healthier drinks led to the revival of traditional and the creation of innovative beverages. Various protein-rich legumes were used for milk analogues, which might be also valuable raw materials for refreshing, protein-rich beverages. However, no such applications have been marketed so far, which might be due to unpleasant organoleptic impressions like the legume-typical “beany” aroma. Lactic acid fermentation has already been proven to be a remedy to overcome this hindrance in consumer acceptance.ResultsIn this study, a statistically based approach was used to elucidate the impact of the fermentation parameters temperature, inoculum cell concentration, and methionine addition on the fermentation of lupine- and faba bean-based substrates. A total of 39 models were found and verified. The majority of these models indicate a strong impact of the temperature on the reduction of aldehydes connected to the “beany” impression (e.g., hexanal) and on the production of pleasantly perceived aroma compounds (e.g., β-damascenone). Positively, the addition of methionine had only minor impacts on the negatively associated sulfuric compounds methional, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide. Moreover, in further fermentations, the time was added as an additional parameter. It was shown that the strains grew well, strongly acidified the both substrates (pH ≤ 4.0) within 6.5 h, and reached cell counts of > 9 log10 CFU/mL after 24 h. Notably, most of the aldehydes (like hexanal) were reduced within the first 6–7 h, whereas pleasant compounds like β-damascenone reached high concentrations especially in the later fermentation (approx. 24–48 h).ConclusionsOut of the fermentation parameters temperature, inoculum cell concentration, and methionine addition, the temperature had the highest influence on the observed aroma and taste active compounds. As the addition of methionine to compensate for the legume-typical deficit did not lead to an adverse effect, fortifying legume-based substrates with methionine should be considered to improve the bioavailability of the legume protein. Aldehydes, which are associated with the “beany” aroma impression, can be removed efficiently in fermentation. However, terminating the process prematurely would lead to an incomplete production of pleasant aroma compounds.

Unlocking the potential of Kluyveromyces marxianus in the definition of aroma composition of cheeses.

The cheese microbiota is very complex and is made up of technologically-relevant, spoilage, opportunistic and pathogenic microorganisms. Among them lactic acid bacteria and yeasts are the main ones. One of the most interesting dairy yeasts is Kluyveromyces marxianus because of its technological properties including the ability to produce aroma compounds. This study investigated the contribution of Kluyveromyces marxianus to the gross composition and aroma profile of cow cheeses. Experimental cheeses were prepared by inoculating a co-culture of K. marxianus FM09 and a commercial strain of Lacticaseibacillus casei and compared with cheeses obtained with only L. casei. The gross composition was determined by a FoodScan™ 2 Dairy Analyser, and free amino acids were evaluated at 507 nm after reaction with Cd-ninhydrin. The volatile organic compounds were extracted by head-space solid phase micro-extraction and analyzed by gas chromatography-mass spectrometry coupled with odor activity values. qRT-PCR was applied to determine the expression of genes involved in esters synthesis and degradation. The inoculation of K. marxianus induced an increase of pH and a reduction of protein content of cheeses, in agreement with the stronger proteolysis detected in these cheeses. K. marxianus influenced the content of aroma compounds both quantitatively and qualitatively. In particular, an increase of higher alcohols, esters and organic acids was observed. Moreover, 12 compounds were detected only in cheeses obtained with the co-culture. These differences were in agreement with the odor activity values (OAV). In fact, only 11 compounds showed OAV > 1 in cheeses obtained with the commercial strain, and 24 in those obtained with the co-culture. The qPCR analysis revealed an over expression of ATF1, EAT1, and IAH1 genes. Kluyveromyces marxianus could act as an important auxiliary starter for cheese production through the development and diversification of compounds related to flavor in short-aged cow cheeses.

Directed evolution and metabolic engineering generate an Escherichia coli cell factory for de novo production of 4-hydroxymandelate

4-hydroxymandelate is a high-value aromatic compound used in the medicine, cosmetics, food, and chemical industry. However, existing natural extraction and chemical synthesis methods are costly and lead to environmental pollution. This study employed metabolic engineering and directed evolution strategies for de novo 4-hydroxymandelate biosynthesis. Two key challenges were addressed: insufficient precursor supply and limited activity of crucial enzymes. Through gene overexpression and multi-level gene interference using CRISPRi, An Escherichia coli chassis capable of producing the key precursor 4-hydroxyphenylpyruvate and the titer reached 5.05 mM (0.91 g/L). A mutant clone was obtained, HmaSV152G, which showed a 5.13-fold improvement in the catalytic rate. During fermentation, a high production of 194.87 mM (32.768 g/L) 4-hydroxymandelate was achieved in 76 h with a batch supply of glucose in a 5-L bioreactor. This study demonstrated the great potential of biosensors in protein engineering and provides a reference for large-scale production of other high-value aromatic compounds.

Efficient selective cleavage of C−C bonds in lignin under visible light enabled by the Fe-doped mesoporous graphitic carbon nitride photocatalyst

To obtain high-valued aromatic products, it is paramount to cleave the Cα−Cβ bonds in lignin under mild conditions selectively. Nevertheless, this task remains daunting due to the formidable dissociation energies and steric hindrance associated with these bonds. Herein, a facile, efficient and cost-effective strategy for selectively breaking the Cα−Cβ bond in lignin with visible-light irradiation and room temperature is proposed, facilitated by the utilization of the ferric-doped mesoporous graphitic carbon nitride (Fe/mpg-CN) photocatalyst. Collective contributed by the reduced band gap and photoluminescence, combined with intensified visible-light absorption and enhanced photocurrent, the effectiveness in photocatalytic activity of Fe/mpg-CN is offered. Specifically, a high conversion rate (98 %) of the lignin model compound (2-phenoxy-1-phenylethanol), coupled with an excellent selectivity of 98 % in cleaving the Cα−Cβ bonds is achieved by Fe/mpg-CN. Photogenerated holes are indicated as the main active species through comprehensive mechanistic investigations. Additionally, the successful photocatalytic depolymerization of the complex dimer model compound (conversion rate ∼ 96 %) and pine kraft lignin further corroborate the satisfying photocatalytic activity and selectivity of Fe/mpg-CN. This study introduces a promising and viable strategy for the selective breaking of lignin through photocatalysis, offering significant implications for the sustainable production of valuable aromatic compounds.

Integrated approach for co-production of bioethanol and light aromatics from lignocellulose through polyethylene glycol-aided acidic glycerol pretreatment

Acid-catalyzed glycerol organosolv (GO) pretreatment is a promising method for lignocellulosic biomass (LCB) fractionation. However, this method often leads to lignin repolymerization, intensifying lignin's inhibitory effects on subsequent enzymatic hydrolysis and limiting the production of highly active lignin, thereby hindering its valorization. This study explored incorporating polyethylene glycol (PEG) into acidic-catalyzed GO to improve bioethanol and bio-oil yields, with a focus on improving the yield of light aromatics, from LCB. Optimized PEG-aided GO pretreatment achieved a significantly higher bioethanol yield (23.7 g/L) compared to GO (17 g/L) and dilute acid (DA: 11.3 g/L) pretreatments. This improvement is attributed to the ability of PEG to mitigate lignin inhibition and modify the physicochemical properties of the pretreated substrate. Furthermore, thermal pyrolysis of PEG-aided GO lignin, obtained after the fermentation process, resulted in a substantially increased bio-oil yield (45.5 %) compared to GO (19 %) and DA (12 %). The enhanced bio-oil yield from PEG-aided GO lignin is ascribed to the promotion of β-O-4 linkages and the formation of β-O-4′ linkages. Characterization of the pyrolysis bio-oil revealed that light aromatic compounds were the dominant fraction, with their relative abundance significantly increasing from DA (5.9 %) to GO (9.7 %) and PEG-aided GO lignin (24.9 %). The PEG-aided GO method achieved an energy output of 8.85 MJ/kg, exceeding that of the GO and DA methods by 31 % and 57 %, respectively. The energy conversion efficiency of the PEG-aided GO method was 70 %, demonstrating a significant improvement compared to GO (57 %) and DA (51 %). This approach promotes the circular economy by upcycling LCB for bioethanol and valuable light aromatic compound production.

Microbial production of aromatic compounds and synthesis of high-performance bioplastics.

Microbial fermentation has provided fermented foods and important chemicals such as antibiotics, amino acids, and vitamins. Metabolic engineering of synthetic microbes has expanded the range of compounds produced by fermentation. Petroleum-derived aromatic compounds are widely used in industry as raw materials for pharmaceuticals, dyes, and polymers and are in great demand. This review highlights the current efforts in the microbial production of various aromatic chemicals such as aromatic amines, cinnamic acid derivatives, and flavoring aromatics, including their biosynthesis pathways. In addition, the unique biosynthetic mechanism of pyrazine, a heterocyclic compound, from amino acids is described to expand the use of biomass-derived aromatic compounds. I also discuss our efforts to develop high-performance bioplastics superior to petroleum plastics from the aromatic compounds produced by microbial fermentation.

Identification of promising lactic acid bacteria for the fermentation of lupine‐ and faba bean‐based substrates to produce refreshing protein‐rich beverages—A strain screening

AbstractLupines and faba beans are rising stars among legumes as sources of valuable, vegan plant‐based proteins. To enter new application areas like the production of protein‐rich refreshing beverages, the typical beany aroma impression has to be overcome, and the sensory appearance has to be improved, as it can be accomplished with lactic acid fermentation. An extensive strain screening of 70 lactic acid bacteria from 16 genera was performed to identify suitable strains to transform substrates made from lupines and faba beans into refreshing beverages and to improve their sensory characteristics. By analyzing carbohydrate utilization, production of organic acids and aroma compounds, and sensory appearance, 22 strains for lupine and eight strains for faba bean were preselected. Subsequently, the most suitable strains (five for lupine and three for faba beans) were identified by a trained sensory panel, and finally their growth kinetics were discussed. Generally, the aroma profile varied highly with the utilized strain. However, by selecting suitable strains, the beany impression can be highly reduced and pleasant aroma impressions (e.g., fruity and buttermilk) can be added. Most strikingly, it was proven that using germinated lupines and faba beans instead of raw ones can bypass the usual growth restriction, and the strain selection can be focused exclusively on sensory aspects. This opens the option to use strains usually excluded for the fermentation of legumes due to their lack of utilization of the legume‐typical α‐galactosides.

Influence of Cheese Composition on Aroma Content, Release, and Perception.

The quality of a cheese is determined by the balance of aroma compounds primarily produced by microorganisms during the transformation of milk into ripened cheese. The microorganisms, along with the technological parameters used in cheese production, influence aroma formation. The perception of these compounds is further influenced by the composition and structure of the cheese. This study aimed to characterize how cheese composition affects aroma compound production, release, and perception. Sixteen cheeses were produced under controlled conditions, followed by a quantitative descriptive analysis post ripening. Aroma composition was analyzed using HS-SPME-GC-MS, and a dynamic sensory evaluation (TCATA) was combined with nosespace analysis using PTR-ToF-MS. Image analysis was also conducted to characterize cheese structure. Cheese fat and whey lactose contents were identified as key factors in the variability of sensory attributes. GC-MS analyses identified 27 compounds correlated with sensory attributes. In terms of aroma compound release, 23 ions were monitored, with fat, salt, and lactose levels significantly affecting the release of most compounds. Therefore, cheese fat, salt, and whey lactose levels, as well as the types of microbial strains, play a role in influencing the composition, structure, release of aroma compounds, and sensory perception.

Biomass Valorization through Catalytic Pyrolysis Using Metal-Impregnated Natural Zeolites: From Waste to Resources.

Catalytic biomass pyrolysis is one of the most promising routes for obtaining bio-sustainable products that replace petroleum derivatives. This study evaluates the production of aromatic compounds (benzene, toluene, and xylene (BTX)) from the catalytic pyrolysis of lignocellulosic biomass (Pinus radiata (PR) and Eucalyptus globulus (EG)). Chilean natural zeolite (NZ) was used as a catalyst for pyrolysis reactions, which was modified by double ion exchange (H2NZ) and transition metals impregnation (Cu5H2NZ and Ni5H2NZ). The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), ammonium programmed desorption (TPD-NH3), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) allowed us to study the influence of natural and modified zeolite catalysts on BTX production. XRD analysis confirmed the presence of metal oxides (CuO and NiO) in the zeolite framework, and SEM-EDS confirmed successful metal impregnation (6.20% for Cu5H2NZ and 6.97% for Ni5H2NZ). Py-GC/MS revealed a reduction in oxygenated compounds such as esters, ketones, and phenols, along with an increase in aromatic compounds in PR from 2.92% w/w (without catalyst) to 20.89% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/5, and in EG from 2.69% w/w (without catalyst) to 30.53% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/2.5. These increases can be attributed to acidic sites within the catalyst pores or on their surface, facilitating deoxygenation reactions such as dehydration, decarboxylation, decarbonylation, aldol condensation, and aromatization. Overall, this study demonstrated that the catalytic biomass pyrolysis process using Chilean natural zeolite modified with double ion exchange and impregnated with transition metals (Cu and Ni) could be highly advantageous for achieving significant conversion of oxygenated compounds into hydrocarbons and, consequently, improving the quality of the condensed pyrolysis vapors.

Efficient and selective cleavage of lignin C–C bonds under visible light facilitated by the Zn(II)-doped mesoporous graphitic carbon nitride photocatalyst

Despite the promise of photocatalysis for extracting aromatic compounds from renewable lignin feedstocks, the selective cleavage of Cα–Cβ bonds in lignin under mild conditions poses a persistent challenge, primarily due to their elevated dissociation energies and steric hindrance. Herein, an efficient photocatalytic strategy for selectively breaking the Cα–Cβ bonds of lignin with visible-light irradiation and room temperature is proposed, facilitated by the Zn(II)-doped porous graphitic carbon nitride (Zn/CN) photocatalyst. Reduced energy band gap and photoluminescence, along with intensified visible-light absorption and enhanced photocurrent of Zn/CN, contribute to its efficacy in photocatalytic activity. Consequently, the lignin model compound (2-phenoxy-1-phenylethanol) achieves a conversion rate of 99 %, demonstrating a notable selectivity of 97 % in specifically breaking the Cα–Cβ bonds. Mechanistic investigations identify that photogenerated holes play a pivotal role during the photocatalytic conversion. Additionally, the activity and selectivity of Zn/CN photocatalyst are further confirmed by the successful photocatalytic conversion of pine kraft lignin, yielding high-value chemicals such as benzoic acid and vanillin. This research proposes an economical, efficient, and facile method for utilizing renewable lignin feedstocks under photocatalysis, thus advancing the production of high-value aromatic compounds.

Eugenol transport and biosynthesis through grafting in aromatic plants of the Ocimum genus.

Aromatic compounds play essential roles in plant physiology and various industries because of their unique fragrances and beneficial properties. In this study, we investigated the transport and biosynthesis of eugenol, a prominent aromatic compound, within the Ocimum genus, using grafting experiments. Grafting sweet basil (Ocimum basilicum) scions onto diverse rootstocks, including tobacco (Nicotiana benthamiana) and thyme (Thymus vulgaris), revealed that eugenol is transported from the shoot to the root across distinct plant species. Furthermore, grafting within the Ocimum genus, which includes O. basilicum, O. tenuiflorum, and O. americanum, resulted in variations in eugenol transport and accumulation. The eugenol content in the shoots remained constant across all combinations, whereas the root eugenol levels varied depending on the scion-rootstock pair. To elucidate the biosynthetic capabilities of eugenol in Ocimum roots, we performed in vitro enzyme assays using crude protein extracts from roots, which revealed that eugenol can be synthesized in roots in addition to being transported. Expression analysis of eugenol synthase (EGSs) genes showed that EGS4 expression was influenced by grafting in O. basilicum roots, suggesting compensation by other EGSs. Our results suggest that eugenol transport and biosynthesis are multifaceted processes influenced by the interactions between different species and tissues. The potential to engineer eugenol levels in rootstocks lacking biosynthetic capacity has potential applications in agriculture and industry. This study reveals the dynamic interplay between eugenol transport and biosynthesis in the Ocimum genus, providing insights into the manipulation of aromatic compound production in plants.

Effect of Hanseniaspora vineae and Saccharomyces cerevisiae co-fermentations on aroma compound production in beer

In recent years, the boom of the craft beer industry refocused the biotech interest from ethanol production to diversification of beer aroma profiles. This study analyses the fermentative phenotype of a collection of non-conventional yeasts and examines their role in creating new flavours, particularly through co-fermentation with industrial Saccharomyces cerevisiae. High-throughput solid and liquid media fitness screening compared the ability of eight Saccharomyces and four non-Saccharomyces yeast strains to grow in wort. We determined the volatile profile of these yeast strains and found that Hanseniaspora vineae displayed a particularly high production of the desirable aroma compounds ethyl acetate and 2-phenethyl acetate. Given that H. vineae on its own can't ferment maltose and maltotriose, we carried out mixed wort co-fermentations with a S. cerevisiae brewing strain at different ratios. The two yeast strains were able to co-exist throughout the experiment, regardless of their initial inoculum, and the increase in the production of the esters observed in the H. vineae monoculture was maintained, alongside with a high ethanol production. Moreover, different inoculum ratios yielded different aroma profiles: the 50/50 S. cerevisiae/H. vineae ratio produced a more balanced profile, while the 10/90 ratio generated stronger floral aromas. Our findings show the potential of using different yeasts and different inoculum combinations to tailor the final aroma, thus offering new possibilities for a broader range of beer flavours and styles.

Enhanced Gene Expression in the Biosynthetic Pathway of 2-Acetyl-1-pyrroline in “Hom Bon” Fragrant Native Rice in Response to Varied Light Wavelength Conditions

The development of the Automated Agricultural Cabinet (AAC) prototype was driven by the goal of improving the aromatic qualities of locally grown rice. This compact prototype, designed with attention, employed Arduino programming to investigate genes related to the production of aromatic compounds in rice seedlings under different light conditions, including red, blue and white light. To ensure the reliability of experiments, a controlled environment was maintained at 25 °C and 75 % humidity, and rigorous testing confirmed precise light intensity measurements within the AAC. Results indicated specific light values: 9.25 ± 0.602 for red light, 11.47 ± 0.055 for blue light and 0.91 ± 0.027 µmol·m−²·s−¹ for white light. The study focused on up-regulated genes in 7-day-old ‘Hom Bon’ rice seedlings, revealing a significant increase in P5CS and 1Δ-pyrroline gene expression. These genes are crucial in the biosynthesis pathway of 2-acetyl-1-pyrroline (2-AP), with P5CS acting as a precursor and 1Δ-pyrroline as the final step. Interestingly, the study discovered that when 7-day-old ‘Hom Bon’ rice seedlings were exposed to both red and blue light, gene expression rose dramatically, contrasting when exposed to white light. This finding demonstrates that the wavelength of light exposure influences gene expression in the 2-acetyl-1-pyrroline (2-AP) biosynthetic pathway of ‘Hom Bon’ rice seedlings throughout the 7-day growth stage. This study demonstrates the feasibility of improving the smell of indigenous rice varieties by changing pre-planting light conditions, giving a promising avenue for increased commercial appeal. Furthermore, this project aims to improve the local community’s financial well-being by supporting better farming methods. HIGHLIGHTS The Automated Agricultural Cabinet (AAC) prototype has the capability to select the optimal light wavelength, inducing the up-regulation of genes associated with the 2-AP biosynthetic pathway in “Hom Bon” a fragrant native rice variety In the fragrant native rice variety “Hom Bon” the up-regulated gene in the direct 2-AP pathway, P5CS, exhibited an expression level that was twice as high as that of the housekeeping gene The red and blue wavelengths directly elevated the expression of up-regulated genes associated with the 2-AP biosynthetic pathway GRAPHICAL ABSTRACT