Production Of Higher Alcohols Research Articles

Active learning streamlines development of high performance catalysts for higher alcohol synthesis

Developing efficient catalysts for syngas-based higher alcohol synthesis (HAS) remains a formidable research challenge. The chain growth and CO insertion requirements demand multicomponent materials, whose complex reaction dynamics and extensive chemical space defy catalyst design norms. We present an alternative strategy by integrating active learning into experimental workflows, exemplified via the FeCoCuZr catalyst family. Our data-aided framework streamlines navigation of the extensive composition and reaction condition space in 86 experiments, offering >90% reduction in environmental footprint and costs over traditional programs. It identifies the Fe65Co19Cu5Zr11 catalyst with optimized reaction conditions to attain higher alcohol productivities of 1.1 gHA h−1 gcat−1 under stable operation for 150 h on stream, a 5-fold improvement over typically reported yields. Characterization reveals catalytic properties linked to superior activities despite moderate higher alcohol selectivities. To better reflect catalyst demands, we devise multi-objective optimization to maximize higher alcohol productivity while minimizing undesired CO2 and CH4 selectivities. An intrinsic trade-off between these metrics is uncovered, identifying Pareto-optimal catalysts not readily discernible by human experts. Finally, based on feature-importance analysis, we formulate data-informed guidelines to develop performance-specific FeCoCuZr systems. This approach goes beyond existing HAS catalyst design strategies, is adaptable to broader catalytic transformations, and fosters laboratory sustainability.

Transcriptomic and metabolomic correlation analysis: effect of initial SO2 addition on higher alcohol synthesis in Saccharomyces cerevisiae and identification of key regulatory genes.

Higher alcohols are volatile compounds produced during alcoholic fermentation that affect the quality and safety of the final product. This study used a correlation analysis of transcriptomics and metabolomics to study the impact of the initial addition of SO2 (30, 60, and 90 mg/L) on the synthesis of higher alcohols in Saccharomyces cerevisiae EC1118a and to identify key genes and metabolic pathways involved in their metabolism. Transcriptomics and metabolomics correlation analyses were performed and differentially expressed genes (DEGs) and differential metabolites were identified. Single-gene knockouts for targeting genes of important pathways were generated to study the roles of key genes involved in the regulation of higher alcohol production. We found that, as the SO2 concentration increased, the production of total higher alcohols showed an overall trend of first increasing and then decreasing. Multi-omics correlation analysis revealed that the addition of SO2 affected carbon metabolism (ko01200), pyruvate metabolism (ko00620), glycolysis/gluconeogenesis (ko00010), the pentose phosphate pathway (ko00030), and other metabolic pathways, thereby changing the precursor substances. The availability of SO2 indirectly affects the formation of higher alcohols. In addition, excessive SO2 affected the growth of the strain, leading to the emergence of a lag phase. We screened the ten most likely genes and constructed recombinant strains to evaluate the impact of each gene on the formation of higher alcohols. The results showed that ADH4, SER33, and GDH2 are important genes of alcohol metabolism in S. cerevisiae. The isoamyl alcohol content of the EC1118a-ADH4 strain decreased by 21.003%; The isobutanol content of the EC1118a-SER33 strain was reduced by 71.346%; and the 2-phenylethanol content of EC1118a-GDH2 strain was reduced by 25.198%. This study lays a theoretical foundation for investigating the mechanism of initial addition of SO2 in the synthesis of higher alcohols in S. cerevisiae, uncovering DEGs and key metabolic pathways related to the synthesis of higher alcohols, and provides guidance for regulating these mechanisms.

Impact of Pure, Co-, and Sequential Fermentations with Hanseniaspora sp. and Saccharomyces cerevisiae on the Volatile Compounds of Ciders

Pure, co-, and sequential fermentations of Hanseniaspora uvarum, H. guilliermondii, and Saccharomyces cerevisiae strains were evaluated to improve the aromatic quality of ciders. In sequential fermentations, Hanseniaspora strains were used as starter, followed by S. cerevisiae inoculation succeeding one, two, and three days of fermentation. Kinetics, physicochemical parameters, and volatile compounds were assessed during 10 days of fermentation. The headspace technique was used to capture the volatile compounds from the ciders obtained in each experiment and analyzed by gas chromatography. Fermentations with pure strains of Hansenisaspora sp. showed a high population (>1010 CFU/mL) but had a low fermentation rate (2.3–3.8 CO2 g/L/d), low consumption of amino acids (20–40 mg/L) with a high residual content, high sugar consumption (80–90 g/L), and low alcohol content (<2.0% v/v). The H. uvarum strain produced a notably high ester content (245 mg/L). In the co-fermentations, H. guilliermondii with S. cerevisiae highlighted a significant production of higher alcohols, similar to that produced by S. cerevisiae alone (152–165 mg/L). In general, the maximum fermentation rate of the sequential inoculations was lower than co-fermentations but showed low residual nitrogen content (<69 mg/L) and good conversion of sugars into ethanol (4.3–5.7% v/v). The highest concentrations of volatile compounds were observed in treatments involving the two non-conventional strains: H. uvarum with S. cerevisiae inoculation after three days (564 mg/L) and H. guilliermondii after just one day (531 mg/L) of fermentation. These differences stemmed from the metabolic activity of the strains. H. uvarum was influenced by the presence of Saccharomyces, whereas H. guilliermondii did not exhibit this effect. Thus, a pure H. uvarum inoculum has the potential to produce a demi-sec cider with low alcohol content and high content of esters, contributing to a fruity aroma. In addition, ciders with sequential inoculation were the most promising for dry cider processing concerning fermentation parameters and bioaroma enrichment.

Tailoring the microenvironment of MOF-derived Co nanoparticles for efficient higher alcohol production via Fischer-Tropsch synthesis

Alcohols are considered as high value-added products from Fischer–Tropsch synthesis (FTS). Efficient conversion of syngas into higher alcohols (C2+OH, HA) is of great significance but poses grand challenges. Herein, a series of nitrogen-doped carbon confined Co catalysts (Co@NC and K-Co@NC) have been prepared via pyrolysis of different Co-containing ZIF-67 and K addition by ball milling. After K addition for modulation of the microenvironment of Co-containing catalysts, the K-Co@NC catalysts display an enhanced HA selectivity in FTS, with a maximum HA selectivity up to ∼30 % and a space time yield of HA (STYC2+OH) of 58 mg·gcat−1·h−1, reflecting the highest HA productivities for Co-based heterogeneous catalysts under similar FTS conditions. Comprehensive characterization studies reveal that K addition, could not only modulate the surface basicity for suppressing the side reactions, but also act as electron donors for promoting the formation of Co2C species during the FTS process, facilitating CO non-dissociative adsorption and CO insertion for improving alcohol formation in FTS. This work provides a feasible strategy for the design of highly efficient Co-based FTS catalysts for production of HA by utilizing MOF materials as the scaffolds.

Enhancement of higher alcohols selectivity in Fischer-Tropsch synthesis using Walnut and Almond shell derived biochars as Copper/Cobalt catalyst support

The production of higher alcohols from synthesis gas using biochar-supported copper-cobalt catalysts is investigated. Biochars were prepared via pyrolysis of Walnut shells and Almond shells and were subsequently activated through physical and chemical methods. A 15 wt% Copper and 5 wt% Cobalt was loaded on the activated biochars via the impregnation technique. The chemical and physical properties of the catalysts were studied using various methods. The catalytic performance of the catalysts was assessed in a fixed-bed microreactor at 20 bars, 320 °C, and, an H2/CO ratio of 2, and the results were compared with the γ-Alumina supported catalyst. Strong interaction between cobalt and copper particles and the formation of bimetallic CuCo2O4 species were observed. The catalysts' reducibility was enhanced by a factor of 1.42. The catalytic studies revealed a significant enhancement in the rate of carbon monoxide hydrogenation. The catalyst supported on low-cost Almond shell-derived biochar demonstrated the best performance. The total alcohol selectivity increased from 22.2 wt% to 34.2 wt%, and the C2+ alcohol selectivity rose from 78.3 wt% to 91.1 wt%, as compared to the industrial catalyst supported on alumina. However, the selectivity for C5+ liquid hydrocarbons decreased to 16.8 wt%. Notably, biochar-supported catalysts also exhibited good stability.

Higher Alcohol Synthesis from CO2 Hydrogenation through a CO2/H2O Co-Transport Membrane Reactor

With the rapid development of renewable energy, direct CO2 hydrogenation (CHR) to liquid fuels and value-added chemicals has attracted considerable attention worldwide. Among them, converting the greenhouse gas CO2 into higher alcohols (HAs) is of great significance due to their potential applications as fuel additive and fine chemical intermediates. However, owing to the chemical inertness of CO2 molecules and uncontrollability of C-C coupling, this reaction still suffers from low CO2 conversion, poor HA selectivity and product rate. In this presentation, we show a CO2/H2O co-transport membrane reactor in the presence of multifunctional catalysts to capture CO2 and store H2 in HAs in one step. The results explicitly show that the captured CO2 from flue gas at retentate side can directly react with a sweeping H2 at the permeate side to form liquid chemicals such as HAs with specific catalysts. Due to transportability of H2O, a product of the CHR, from permeate side to retentate side of membrane reactor, the CHR conversion is expected to be shifted towards desirable HAs production. Besides, through gradual addition of CO2 into H2 stream along the membrane length, the tubular CO2/H2O co-transport membrane reactor can create CHR-favorable, high local H2/CO2 ratio for improved CO2 reduction into the reactive C1-species, which is highly desirable to facilitate subsequent C-C coupling and OH insertion to form the wanted HAs.

Yeast strains do have an impact on the production of cured cocoa beans, as assessed with Costa Rican Trinitario cocoa fermentation processes and chocolates thereof.

The microbiological and metabolic outcomes of good cocoa fermentation practices can be standardized and influenced through the addition of starter culture mixtures composed of yeast and bacterial strains. The present study performed two spontaneous and 10 starter culture-initiated (SCI) cocoa fermentation processes (CFPs) in Costa Rica with local Trinitario cocoa. The yeast strains Saccharomyces cerevisiae IMDO 050523, Hanseniaspora opuntiae IMDO 020003, and Pichia kudriavzevii IMDO 060005 were used to compose starter culture mixtures in combination with the lactic acid bacterium strain Limosilactobacillus fermentum IMDO 0611222 and the acetic acid bacterium strain Acetobacter pasteurianus IMDO 0506386. The microbial community and metabolite dynamics of the cocoa pulp-bean mass fermentation, the metabolite dynamics of the drying cocoa beans, and the volatile organic compound (VOC) profiles of the chocolate production were assessed. An amplicon sequence variant approach based on full-length 16S rRNA gene sequencing instead of targeting the V4 region led to a highly accurate monitoring of the starter culture strains added, in particular the Liml. fermentum IMDO 0611222 strain. The latter strain always prevailed over the background lactic acid bacteria. A similar approach, based on the internal transcribed spacer (ITS1) region of the fungal rRNA transcribed unit, was used for yeast strain monitoring. The SCI CFPs evolved faster when compared to the spontaneous ones. Moreover, the yeast strains applied did have an impact. The presence of S. cerevisiae IMDO 050523 was necessary for successful fermentation of the cocoa pulp-bean mass, which was characterized by the production of higher alcohols and esters. In contrast, the inoculation of H. opuntiae IMDO 020003 as the sole yeast strain led to underfermentation and a poor VOC profile, mainly due to its low competitiveness. The P. kudriavzevii IMDO 060005 strain tested in the present study did not contribute to a richer VOC profile. Although differences in VOCs could be revealed in the cocoa liquors, no significant effect on the final chocolates could be obtained, mainly due to a great impact of cocoa liquor processing during chocolate-making. Hence, optimization of the starter culture mixture and cocoa liquor processing seem to be of pivotal importance.

Understanding the formation of higher alcohols in the liquid-phase ethanol condensation over copper-loaded hydrotalcite-derived mixed oxides

The production of higher alcohols (C≥4) via ethanol liquid-phase condensation over different Cu-based catalysts is studied in this work. Experimental results demonstrate that dehydrogenation steps are more relevant than hydrogenation steps, according to the lack of improvement in activity when a bimetallic (Pd-Cu) catalyst. Thus, the sequential hydrogenation via Meerwein-Ponndorf-Verley (MPV) and surface-mediated H-transfer is identified as active enough to obtain the desired alcohols. The best results were obtained with a 20 % Cu/MgAl catalyst, showing more than 10 % of ethanol conversion (free solvent conditions) and 60 % selectivity to higher alcohols (16 % to C6 and C8 ones). Experiments with different feed compositions, including C4 alcohols and acetaldehyde, and a comprehensive analysis of all the results in terms of a mechanistic oligomerization model, demonstrate that the C-C coupling follows a step-growth model where the condensation between monomers coexists with the one involving oligomers.

Characterization and Correlation of Microbiota and Higher Alcohols Based on Metagenomic and Metabolite Profiling during Rice-Flavor Baijiu Fermentation.

Higher alcohol, as an inevitable product of fermentation, plays an important role in the flavor and quality of Baijiu. However, the relationship between the complex microbial metabolism and the formation of higher alcohols in rice-flavor Baijiu was not clear. To investigate the relationship between microorganisms and higher alcohol production, two fermentation mashes inoculated with starters from Heyuan Jinhuangtian Liquor Co., Ltd. (Heyuan, China) as JM and Guangdong Changleshao Co., Ltd. (Meizhou, China) as CM, respectively, with significant differences in higher alcohol profiles during rice-flavor Baijiu fermentation were selected. In general, higher alcohols presented a rapid accumulation during the early fermentation stages, especially in JM, with higher and faster increases than those in CM. As for their precursors including amino acids, pyruvic acid and ketoacids, complex variations were observed during the fermentation. Metagenomic results indicated that Saccharomyces cerevisiae and Rhizopus microsporus were the microorganisms present throughout the brewing process in JM and CM, and the relative abundance of R. microsporus in JM was significantly higher than that in CM. The results of higher alcohol metabolism in JM may contribute to the regulation of higher alcohols in rice-flavor Baijiu.

Microbial Community Dynamics and the Correlation between Specific Bacterial Strains and Higher Alcohols Production in Tartary Buckwheat Huangjiu Fermentation.

Tartary buckwheat is a healthy grain rich in nutrients and medicinal ingredients and consequently is commonly used for Huangjiu brewing. In order to reveal the correlation between microbial succession and higher alcohols production, in this study, Huangjiu fermentation was conducted using Tartary buckwheat as the raw material and wheat Qu as the starter culture. Microbial community dynamics analysis indicated that the bacterial diversity initially decreased rapidly to a lower level and then increased and maintained at a higher level during fermentation. Lactococcus was the dominant bacteria and Ralstonia, Acinetobacter, Cyanobacteria, and Oxalobacteraceae were the bacterial genera with higher abundances. In sharp contrast, only 13 fungal genera were detected during fermentation, and Saccharomyces showed the dominant abundance. Moreover, 18 higher alcohol compounds were detected by GC-MS during fermentation. Four compounds (2-phenylethanol, isopentanol, 1-hexadecanol, and 2-phenoxyethanol) were stably detected with high concentrations during fermentation. The compound 2-ethyl-2-methyl-tridecanol was detected to be of the highest concentration in the later period of fermentation. Correlation analysis revealed that the generation of 2-phenylethanol, isopentanol, 1-hexadecanol, and 2-phenoxyethanol were positively correlated with Granulicatella and Pelomonas, Bacteroides, Pseudonocardia and Pedomicrobium, and Corynebacterium, respectively. The verification fermentation experiments indicated that the improved wheat Qu QT3 and QT4 inoculated with Granulicatella T3 and Acidothermus T4 led to significant increases in the contents of 2-phenylethanol and pentanol, as well as isobutanol and isopentanol, respectively, in the Tartary buckwheat Huangjiu. The findings benefit understanding of higher alcohols production and flavor formation mechanisms in Huangjiu fermentation.

Reducing higher alcohols by integrating indigenous Saccharomyces cerevisiae, nitrogen compensation, and chaptalization methods during fermentation of kiwifruit wine

The concentration of higher alcohols in kiwifruit wine is often excessive, posing the risk of toxic effects on the health of drinkers. To lower the higher alcohol content in kiwifruit wine, this study tested five indigenous S. cerevisiae strains, two types of nitrogen sources (inorganic and organic), and five chaptalization methods. The results showed that the total higher alcohol production of three versions of resulting kiwifruit wines: (i) fermented by S. cerevisiae LFN524, (ii) adding 300 mg/L diammonium phosphate (DAP), using the Th-Tw-S chaptalization strategy, were decreased by 32%, 43%, and 26%, respectively. Integrating the above technologies, that is, fermentation by S. cerevisiae LFN524, the addition of 300 mg/L DAP, and use of Th-Tw-S chaptalization strategy, for pilot-scale kiwifruit wine production, showed a 52% reduction in total higher alcohol production (222.00 ± 24.91 mg/L) and a 14% reduction in total acidity production (13.32 ± 0.06 g/L). In pilot-scale kiwifruit wine, sensory analysis showed that with the reduction of higher alcohol content, the typical aromas of kiwifruit wine became more prominent, resulting in a purer aroma of kiwifruit wine. Taken together, the results of this research provide a viable means for producing lower-higher-alcohol kiwifruit wines.

Approaching Study on the Relationship Between Saccharomyces cerevisiae Production of Tyrosol, Hydroxytyrosol, and Melatonin with Volatile Compounds in Fermented Must

Yeasts are feasible and effective bioreactors and, therefore, there is a great interest in their industrial employment for the production of a wide range of molecules. In this study, the production by Saccharomyces cerevisiae of bioactive compounds such as hydroxytyrosol (HT), tyrosol (TYR) and melatonin (MEL) vs. volatile compounds in fermented must was studied. The concentration of the bioactive compounds HT and MEL in fermented must employing different yeast strains revealed that the higher the concentrations, the lower the amount of volatile compounds determined. This inverse correlation was especially remarkable with respect to the production of higher alcohols, especially 2-phenylethanol (2-PE) and esters. Furthermore, the employment of a modified Aro4pK229LS. cerevisiae QA23 yeast strain which overproduces HT, gave rise to fermented must also higher in 2-PE and their corresponding esters but with an outstanding less presence of other important esters such as ethyl hexanoate and ethyl octanoate. Both premises could point out that S. cerevisiae might have different approaches to handling cell stress/toxicity due to their nitrogen metabolism. One detoxifying pathway could be through the production of higher alcohols and these in turn to esters and the other be more related to synthesizing antioxidant molecules such as MEL and HT.

CO2 hydrogenation for the production of higher alcohols: Trends in catalyst developments, challenges and opportunities

Higher alcohol (HA) synthesis via the hydrogenation of CO2 constitutes a relatively new and exciting field of research that has the potential to help towards the de-carbonization of the energy sector. The process poses formidable challenges, as it demands the formation of at least one C-C bond, when CO2 is thermodynamically stable, fully oxidized and kinetically inert. This work provides a comprehensive and critical literature review of the catalytic formulations that have been employed, in both fixed-bed and batch reactors, which include noble metal catalysts, transition metal-based systems, post-transition metal catalysts, bimetallic, multimetallic/multifunctional catalysts, Metal Organic Frameworks (MOFs), perovskite-, and zeolite-based catalysts. The critical role of promoters and supports and the effect that the reaction conditions have on performance are also discussed. Emphasis has been given to single atom catalysts (SACs), as the high specific activity of these systems seems to hold great promise for the reaction at hand. Breakthroughs made by employing the concept of tandem catalysis are also critically analyzed. This review paper also discusses the thermodynamic aspects of the reaction and the insights that have been gained regarding the reaction mechanism. Finally, it provides an overview of the direction that research may move to into the future.

K–ZrO2 Interfaces Boost CO2 Hydrogenation to Higher Alcohols

Alkali metal promoters are widely used to modify active metal sites/interfaces of heterogeneous catalysts for numerous industrial processes. However, the interplay between an alkali metal and support, a crucial catalytic parameter, has been scarcely investigated in controlling the activation behaviors of intermediates and improving catalysis. Herein, we report that K–ZrO2 interfaces can boost the production of higher alcohols (HA) from CO2 hydrogenation over an amorphous ZrO2-supported K–Cu–Fe catalyst (KFeCu/a-ZrO2). In situ spectroscopy and chemisorption demonstrate that the strong interactions between K and ZrO2 induce the formation of surface Zrδ+ sites/oxygen vacancies at K–ZrO2 interfaces, thus providing plenty of nondissociative CO activation sites. The improved molecular CO adsorption capacity at the K–ZrO2 interfaces expedites the CO insertion reaction (*CHx + *CO → *CHx-CO) at Cu–Fe5C2 interfaces, thereby driving the HA synthesis reaction with nearly 4.6 times higher activity of HA in comparison to the KFeCu/SiO2 catalyst. At the optimal conditions of 320 °C, 4 MPa, and 12 L gcat–1 h–1, the KFeCu/a-ZrO2 catalyst shows the HA space time yield of 125.0 mg gcat–1 h–1, ranking the top level among the reported single-component catalysts in the literature. Most importantly, this work provides an in-depth insight into alkali promoter–support interactions for promoting catalytic performance.

Advances in biosynthesis of higher alcohols in Escherichia coli.

In recent years, the development of green energy to replace fossil fuels has been the focus of research. Higher alcohols are important biofuels and chemicals. The production of higher alcohols in microbes has gained attention due to its environmentally friendly character.Higher alcohols have been synthesized in model microorganism Escherichia coli, and the production has reached the gram level through enhancement of metabolic flow, the balance of reducing power and the optimization of fermentation processes. Sustainable bio-higher alcohols production is expected to replace fossil fuels as a green and renewable energy source. Therefore, this review summarizes the latest developments in producing higher alcohols (C3-C6) by E. coli, elucidate the main bottlenecks limiting the biosynthesis of higher alcohols, and proposes potential engineering strategies of improving the production of biological higher alcohols.This review would provide a theoretical basis for further research on higher alcohols production by E. coli.

Thiamine and Biotin: Relevance in the Production of Volatile and Non-Volatile Compounds during Saccharomyces cerevisiae Alcoholic Fermentation in Synthetic Grape Must.

Vitamins are major cofactors to numerous key metabolic pathways in enological yeasts, and both thiamine and biotin, notably, are believed to be essential to yeast fermentation and growth, respectively. In order to further assess and clarify their role in winemaking, and in the resulting wine, alcoholic fermentations of a commercial Saccharomyces cerevisiae active dried yeast were conducted in synthetic media containing various concentrations of both vitamins. Growth and fermentation kinetics were monitored and proved the essential character of biotin in yeast growth, and of thiamine in fermentation. The synthetic wine volatile compounds were quantified, and notable influences of both vitamins appeared, through a striking positive effect of thiamine on the production of higher alcohols, and of biotin on fatty acids. Beyond the evidence of this influence on fermentations and on the production of volatiles, this work proves, for the first time, the impact held by vitamins on wine yeasts' exometabolome, investigated through an untargeted metabolomic analysis. This highlighted chemical differences in the composition of synthetic wines through a notably marked influence of thiamine on 46 named S. cerevisiae metabolic pathways, and especially in amino acid-associated metabolic pathways. This provides, overall, the first evidence of the impact held by both vitamins on the wine.

Production of biofuels from C1 -gases with Clostridium and related bacteria-Recent advances.

Clostridium spp. are suitable for the bioconversion of C1 -gases (e.g.,CO2 , CO and syngas) into different bioproducts. These products can be used as biofuels and are reviewed here, focusing on ethanol, butanol and hexanol, mainly. The production of higher alcohols (e.g., butanol and hexanol) has hardly been reviewed. Parameters affecting the optimization of the bioconversion process and bioreactor performance are addressed as well as the pathways involved in these bioconversions. New aspects, such as mixotrophy and sugar versus gas fermentation, are also reviewed. In addition, Clostridia can also produce higher alcohols from the integration of the Wood-Ljungdahl pathway and the reverse ß-oxidation pathway, which has also not yet been comprehensively reviewed. In the latter process, the acetogen uses the reducing power of CO/syngas to reduce C4 or C6 fatty acids, previously produced by a chain elongating microorganism (commonly Clostridium kluyveri), into the corresponding bioalcohol.

The synthesis of higher alcohols from CO2 hydrogenation over Mn-Cu-K modified Fe5C2 and CuZnAlZr tandem catalysts

The catalytic production of higher alcohols (HAs) is a promising path for converting CO2 into value-added chemical products. The application is still limited by the low selectivity of HAs (less than 10%) on most catalysts. Here, we report a tandem catalyst consisting of Mn-Cu-K modified iron carbide and CuZnAlZr catalyst. The modification of iron carbide with Mn, Cu and K promoters improves the formation of HAs (13.5% Sel.), and the construction of tandem catalysts with CuZnAlZr can further enhance the catalytic performance. By examining different catalyst filling methods and the filling ratio of the tandem catalyst, it was found that the powder mixing resulted in a higher selectivity of HAs with a mass ratio of the two components of 1:1, and a synergistic effect leads to a higher selectivity of HAs (15.5%) with about 40% of propanol and butanol among HAs.

Biocatalytic aminohydroxylation of styrenes for efficient synthesis of enantiopure β-amino alcohols

A general biocatalytic process of intermolecular aminohydroxylation of styrenes with aniline has been achieved for efficient one-pot preparation of enantiopure β-amino alcohols. The reaction involves first asymmetric epoxidation of alkene substrates by a heme-dependent monooxygenase (P450) or the FAD-dependent styrene monooxygenase, followed by the aminolysis of nascent epoxide intermediates with aniline in water solution. Hybrid cluster-continuum (HCC) model calculations reveal the mechanism of the aminolysis of epoxide with aniline as well as the critical role of the water in mediating such a reaction. In addition, the combined experiments with simulations demonstrate that the chirality of amino alcohol is determined by the absolute configuration of the epoxide formed in the enzymatic reaction. In conclusion, the developed biocatalytic process provides an efficient, environmentally friendly approach for production of high value-added enantiopure β-amino alcohols, starting from cheap and readily available alkenes.

Using transcriptomics to reveal the molecular mechanism of higher alcohol metabolism in Saccharomyces cerevisiae

High alcohols are important flavor compounds in alcoholic beverages, but high concentration of high alcohols is harmful to human health. Higher alcohol synthesis pathways in brewing microorganisms have been investigated, but the interactions between key genes remain to be explored, especially in industrial strains of Saccharomyces cerevisiae. The PDC1 gene was considered to be the main encoding gene of α-keto acid decarboxylase, and its deletion resulted in a 92.23% increase in isobutanol production and a 14.89% decrease in isoamyl alcohol production. Transcriptome sequencing was used to explore the effects of PDC1 gene deletion on global gene transcription levels, and deletion strategies were utilized to verify the effects of differential genes on higher alcohol production. Deletion of differential gene HMLALPHA2 increased isobutanol production by 26.23%, and decreased isoamyl alcohol and 2-phenylethanol production by 30.31% and 22.35%, respectively. The THI2, THI4, THI20 genes were proved to be related to n-propanol synthesis. In addition, HMRA2 and SIR3 genes were found to influence isoamyl alcohol synthesis pathways, and their deletion increased isoamyl alcohol production by 25.18% and 21.76%. Our discovery of new target genes is useful for elucidating the molecular mechanisms of higher alcohols and the construction of novel low-producing higher alcohol strains.