Glycerol Feeding Research Articles

Reducing Organic Load From Industrial Residual Process Brine With a Novel Halophilic Mixed Culture: Scale-Up and Long-Term Piloting of an Integrated Bioprocess.

Integrating bioprocess solutions for treatment and subsequent reuse of saline residual process brine into industrial processes could increase the sustainability of production chains. However, such bioprocesses require large-scales and a robust operation over a prolonged period. Consequently, the aim of this study was to analyze scale-up equivalence as well as continuous and stable process performance of a previously established lab scale process for the degradation of organic contaminants (formate and aromatic compounds) in an industrial context. To that end, a pilot-scale bubble column bioreactor system equipped with a membrane-based cell retention system for process intensification was integrated at an industrial production site. The process was successfully scaled-up and continuously operated for more than 210days. Overall, the process proved to be robust towards changing compositions of the residual process brine stream and degradation rates for organic contaminants were close to 100%. Interestingly, due to the unsterile process conditions, the original Haloferax mediterranei culture was replaced by a novel halophilic bacterial community consisting of three bacterial genera. To further improve process economics and productivity, an optimization of the co-substrate feeding strategy for glycerol is required, as results indicated a potential correlation between glycerol feeding and formate degradation rates. To that end, decoupling of the glycerol feeding from the residual process brine feed is a potential way to increase process control options and allow for easy adaptation of the process to changing residual process brine compositions. Ultimately, the process described here could be a promising alternative for chemical or physical methods of treating residual process brine and once more underlines the potential to exploit natural microbial diversity for industrial purposes.

Direct control of recombinant protein production rates in E. coli fed-batch processes by nonlinear feedback linearization

Biotechnological cultivation processes aim for high and long lasting productivities. In this paper, a method to directly control the productivity of a recombinantly produced protein in an E. coli fed-batch process is introduced. After modeling the process using a nonlinear kinetic model, which includes the degeneration of the product formation capacities, a controller was derived by feedback linearization. The derived control law presents an improved and novel approach to directly influence the process parameter associated with the biomass specific product formation rate. In order to deal with observed model-plant mismatches a Two-Degrees-of-Freedom controller was implemented. A simulation study using different model parameters derived from calibration and validation data sets and two realistic measurement scenarios was carried out to demonstrate the potential of the presented method in comparison to a constant substrate addition. Compared to optimized, constant glycerol feed rates the simulations with controlled productivities led to significantly higher specific titers with the same amount of fed glycerol. The feeding rates given by the developed controller minimize the metabolic load as well as product release and therefore stabilizes the productivity for a prolonged, potentially continuous, production process.

EFFECT OF CRUDE GLYCEROL SUPPLEMENTATION VIA DRINKING WATER ON LAMBS PERFORMANCE, SOME BLOOD HAEMATOLOGY, AND BIOCHEMICAL METABOLITES

EFFECT OF CRUDE GLYCEROL SUPPLEMENTATION VIA DRINKING WATER ON LAMBS PERFORMANCE, SOME BLOOD HAEMATOLOGY, AND BIOCHEMICAL METABOLITES

Generic model based control of different specific rates in recombinant E. coli Fed-batch processes

In addition to often reported control of the specific growth rate we show in this contribution a novel method to control the biomass specific substrate uptake as well as the protein production rate during the production phase of microbial fed-batch cultures. The control laws base on a calibrated process model including experimental data sets with different constant glycerol feed rates. The model includes changing growth and production behaviour in function of the induced metabolic stress. Based on the method of non-linear feedback linearization, the control laws were derived from the model, using the glycerol feed rate as the manipulable variable. Considering comparable setpoints at three different levels the effectiveness of the controller as well as their potential to improve the production phase was assessed by simulations. The direct control of product formation rates enables to ensure constant production performance and therefore to reach highest product levels in short time. As a drawback, the controller needs high feed adaption towards the end to counteract the advancing decay of the attainable production rates. This, to a lesser extend, also applies for the growth rate. A constant substrate uptake rate resulted in a valuable alternative to a uncontrolled, constant feed rate during the production phase of recombinant protein production processes.

Glycerol Hydrogenolysis to Produce 1,2-Propanediol in Absence of Molecular Hydrogen Using a Pd Promoted Cu/MgO/Al2O3 Catalyst

The catalytic process of glycerol hydrogenolysis to produce 1,2-propandiol (1,2-PD) in the absence of external hydrogen addition has been investigated. The methanol present in the crude glycerol from a biodiesel production process is used to provide in situ hydrogen produced via methanol steam reforming for the glycerol hydrogenolysis process. This process can reduce the additional cost for the transportation and storage of molecular hydrogen and also reduce the safety risks related to using high hydrogen pressure. It was found that the introduction of Pd onto a Cu/MgO/Al2O3 catalyst significantly improved the glycerol conversion and 1,2-PD selectivity. The pseudo-first-order kinetic results suggested that the promoting effect of Pd is primarily attributed to the enhanced activity for the hydrogenation of acetol, which is the intermediate formed via glycerol dehydration. A 27−3 fractional factorial design experiment was carried out to investigate the impacts of seven single factors and their binary effects on two responses, namely 1,2-PD selectivity and glycerol conversion. The results showed that the glycerol feed concentration has the most significant effect on the 1,2-PD selectivity, such that the 1,2-PD selectivity is lower if a more concentrated glycerol is used as the feedstock; stirring speed, inert gas pressure and water to methanol molar ratio have insignificant effects on the reaction system. The addition of Pd, higher temperature and higher catalyst loading are the essential factors in order to obtain a high selectivity of 1,2-PD and a high glycerol conversion.

Impact of glycerol feeding profiles on STEAP1 biosynthesis by Komagataella pastoris using a methanol-inducible promoter.

Currently, the lack of reliable strategies for the diagnosis and treatment of cancer makes the identification and characterization of new therapeutic targets a pressing matter. Several studies have proposed the Six Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) as a promising therapeutic target for prostate cancer. Although structural and functional studies may provide deeper insights on the role of STEAP1 in cancer, such techniques require high amounts of purified protein through biotechnological processes. Based on the results presented, this work proposes the application, for the first time, of a fed-batch profile to improve STEAP1 biosynthesis in mini-bioreactor Komagataella pastoris X-33 Mut+ methanol-induced cultures, by evaluating three glycerol feeding profiles-constant, exponential, and gradient-during the pre-induction phase. Interestingly, different glycerol feeding profiles produced differently processed STEAP1. This platform was optimized using a combination of chemical chaperones for ensuring the structural stabilization and appropriate processing of the target protein. The supplementation of culture medium with 6 % (v/v) DMSO and 1 M proline onto a gradient glycerol/constant methanol feeding promoted increased biosynthesis levels of STEAP1 and minimized aggregation events. Deglycosylation assays with peptide N-glycosidase F showed that glycerol constant feed is associated with an N-glycosylated pattern of STEAP1. The biological activity of recombinant STEAP1 was also validated, once the protein enhanced the proliferation of LNCaP and PC3 cancer cells, in comparison with non-tumoral cell cultures. This methodology could be a crucial starting point for large-scale production of active and stable conformation of recombinant human STEAP1. Thus, it could open up new strategies to unveil the structural rearrangement of STEAP1 and to better understand the biological role of the protein in cancer onset and progression.

Culture conditions affect Lactobacillus reuteri DSM 17938 ability to perform glycerol bioconversion into 3-hydroxypropionic acid

The platform molecule 3-hydroxypropionic acid (3-HP) can be produced using Lactobacillus reuteri through a two-step bioprocess that involves a growth phase followed by a bioconversion phase. The bioproduction is performed by resting cells that convert glycerol into 3-HP and 1,3-propanediol in fed-batch mode. This work aimed at studying the effect of the growth conditions of L.reuteri DSM 17938 during the first step, on the glycerol bioconversion into 3-HP during the second step. A Plackett and Burman design was carried out to test, in controlled bioreactors, the effect of 11 growth conditions simultaneously, at fixed bioconversion conditions. The supplementation of the growth medium with vitamin B12 and cysteine displayed a negative effect on the 3-HP bioproduction. The addition of glucose, phytone peptone, Tween 80, 1,2-propanediol and betaine in the growth medium, together with a low temperature and an optimal pH of 6.0 during the growth phase increased the bioconversion duration from 56h to 89hat a glycerol feeding rate of 0.5g·h-1. A validating experiment displayed that the 3-HP titer, 3-HP production yield and 3-HP specific production rate were significantly improved by 25 %, 150 % and 61 %, respectively.

The uncoupled microbial fed-batch fermentation optimization based on state-dependent switched system

In the actual microbial fermentation process, excessive or insufficient substrate can produce inhibitory effects on cells growth. The artificial substrate feeding rules by past experiences have great blindness to keep substrate concentration in a given appropriate range. This paper considers that alkali feed depends on pH value of the solution and glycerol feed depends on glycerol concentration of the solution in the uncoupled microbial fed-batch fermentation process, and establishes a state-dependent switched system in which the flow rates of glycerol and alkali, the number of mode switches, the mode sequence and the switching times are prior unknown. To maximize the yield of target product 1,3-Propanediol (1,3-PD), we formulate a switching optimal control problem with the flow rates of glycerol and alkali, the number of mode switches, the mode sequence and the switching times as decision variables, which is a mixed-integer dynamic programming problem. For solving the mixed-integer dynamic programming problem, the control parametrization technique, the time scaling transformation and the embedded system technology are used to obtain an approximate parameter optimization problem. By using a parallel optimization algorithm, we obtain the optimal control strategies. Under the obtained optimal control strategies, the 1,3-PD yield at the terminal time is increased significantly compared with the previous results.

Exergy analysis of glycerol steam reforming in a heat recovery reactor

A detailed exergy analysis was performed for the steam reforming process of glycerol by means of a series of experiments in a bench scale apparatus. The reforming was conducted in a fixed bed reactor, which operated in heat recovery mode by extracting the demanded energy from hot exhaust gases provided by a diesel engine. In order to determine the role of the main operational parameters into the exergy efficiency of the studied process, the experiments were carried out with glycerol feed concentrations in water ranging from 10% up to 90% weight, whereas the outlet reactor temperature was varied from 600 °C up to 800 °C. Detailed exergy balances revealed a compromise between the exergy destruction within the reforming reactor and liquid separator versus the exergy losses associated to the tar and char outputs. This trade-off was favourable to the 50% and 70% glycerol feed concentration regimes and plateaus of about 74% exergy efficiency and 24 MJ/kg dry syngas exergy content were verified from 650 to 800 °C reactor temperatures.

Enhanced human lysozyme production by Pichia pastoris via periodic glycerol and dissolved oxygen concentrations control.

In human lysozyme (hLYZ) production by Pichia pastoris, the glycerol fed-batch phase was generally implemented under the environment of "oxygen sufficient-glycerol limited" to achieve high cell-density cultivation during the cell growth phase. However, the structural and functional components in P. pastoris cells were irreversible damaged with more and more reactive oxygen species (ROS) accumulation when cells were exposed to the oxygen sufficient environments for long time, leading to a failure of hLYZ expression. In this study, a novel periodic glycerol and dissolved oxygen concentration (DO) control strategy was proposed to solve these problems. This strategy periodically switched the cultivation environments from "oxygen sufficient-glycerol limited" to "oxygen limited-glycerol sufficient" for 5 cycles. When using this strategy: (1) the highest dry cell weight (DCW) of 143.02 g-DCW/L and the lowest distribution of glycerol towards to cell maintenance (0.0400 1/h) were achieved during the glycerol feeding phase by maintaining ROS levels below 48.39 Fluorescence intensity/g-DCW; (2) the adaption time of P. pastoris cells to methanol induction environments was shortened for about 50%; (3) P. pastoris cell metabolic activities reflected by the activities of alcohol oxidase, formaldehyde dehydrogenase, formate dehydrogenase, and methanol consumption rate, etc., in the successive induction phase were largely enhanced; (4) hLYZ activity reached the highest level of 2.45 × 105 IU/mL, which was about 2-fold than that obtained with the strategy of "oxygen sufficient-glycerol limited," when the same methanol induction strategy was adopted. KEY POINTS: • A novel periodic glycerol feeding strategy proposed/used for P. pastoris cell growth. • Higher cell density was obtained by controlling ROS at low level via this strategy. • The highest hLYZ activity was achieved when initiating induction at higher cell density.

Enhancement of polyhydroxyalkanoate production by co-feeding lignin derivatives with glycerol in Pseudomonas putida KT2440

BackgroundEfficient utilization of all available carbons from lignocellulosic biomass is critical for economic efficiency of a bioconversion process to produce renewable bioproducts. However, the metabolic responses that enable Pseudomonas putida to utilize mixed carbon sources to generate reducing power and polyhydroxyalkanoate (PHA) remain unclear. Previous research has mainly focused on different fermentation strategies, including the sequential feeding of xylose as the growth stage substrate and octanoic acid as the PHA-producing substrate, feeding glycerol as the sole carbon substrate, and co-feeding of lignin and glucose. This study developed a new strategy—co-feeding glycerol and lignin derivatives such as benzoate, vanillin, and vanillic acid in Pseudomonas putida KT2440—for the first time, which simultaneously improved both cell biomass and PHA production.ResultsCo-feeding lignin derivatives (i.e. benzoate, vanillin, and vanillic acid) and glycerol to P. putida KT2440 was shown for the first time to simultaneously increase cell dry weight (CDW) by 9.4–16.1% and PHA content by 29.0–63.2%, respectively, compared with feeding glycerol alone. GC–MS results revealed that the addition of lignin derivatives to glycerol decreased the distribution of long-chain monomers (C10 and C12) by 0.4–4.4% and increased the distribution of short-chain monomers (C6 and C8) by 0.8–3.5%. The 1H–13C HMBC, 1H–13C HSQC, and 1H–1H COSY NMR analysis confirmed that the PHA monomers (C6–C14) were produced when glycerol was fed to the bacteria alone or together with lignin derivatives. Moreover, investigation of the glycerol/benzoate/nitrogen ratios showed that benzoate acted as an independent factor in PHA synthesis. Furthermore, 1H, 13C and 31P NMR metabolite analysis and mass spectrometry-based quantitative proteomics measurements suggested that the addition of benzoate stimulated oxidative-stress responses, enhanced glycerol consumption, and altered the intracellular NAD+/NADH and NADPH/NADP+ ratios by up-regulating the proteins involved in energy generation and storage processes, including the Entner–Doudoroff (ED) pathway, the reductive TCA route, trehalose degradation, fatty acid β-oxidation, and PHA biosynthesis.ConclusionsThis work demonstrated an effective co-carbon feeding strategy to improve PHA content/yield and convert lignin derivatives into value-added products in P. putida KT2440. Co-feeding lignin break-down products with other carbon sources, such as glycerol, has been demonstrated as an efficient way to utilize biomass to increase PHA production in P. putida KT2440. Moreover, the involvement of aromatic degradation favours further lignin utilization, and the combination of proteomics and metabolomics with NMR sheds light on the metabolic and regulatory mechanisms for cellular redox balance and potential genetic targets for a higher biomass carbon conversion efficiency.

Glycerol effects on silver catfish (Rhamdia quelen) fingerling feeding: Morphometric, zootechnical and blood parameters

Decreasing natural fossil fuel stocks have supported the use of alternative fuels and increased the availability of glycerol, a biodiesel manufacture by-product. The use of glycerol in animal feed has been extensively investigated and reported as a potential energy source for different fish species. The aim of the present study was to evaluate the effect of crude glycerol as a corn substitute in the feeding of silver catfish fingerlings and on their zootechnical performance and blood parameters. One thousand and five hundred silver catfish fingerlings with an average weight of 1.5 ± 0.03 g were distributed in 301,000 L water tanks in a completely randomized design comprising six treatments (0, 20, 40, 60, 80 and 100% replacement of corn by glycerol) and five repetitions. The experimental period was of 75 days and the diet consisted of three daily meals until apparent satiety. Corn replacement by glycerol at up to 100% did not affect morphometric parameters, zootechnical performance, survival and calcium, cholesterol, alkaline phosphatase, total protein, oxalacetic and pyruvic glutamic transaminase and triglyceride blood parameters, although the plasma glucose rate of silver catfish fingerlings was significantly influenced (P < 0.05). It is concluded that the raw glycerol produced from biodiesel exhibits good potential for use as a corn substitute in silver catfish diets, and that the fingerlings of this species display the capacity to use up to 7.5% of glycerol inclusion or even total corn substitution without affecting morphometric and performance parameters or causing health damage.

Effect of glycerol as an energy source with or without probiotic on carcass trait, litter moisture per cent, haematological and serum metabolites in broiler chicken

An experiment was conducted to access glycerol feeding on the carcass traits, litter moisture %, haematological and serum metabolites of broiler chicken. The broiler chicks were randomly distributed in five groups, viz. T0 (0% glycerol), T1 (3% glycerol with probiotic), T2 (3% glycerol without probiotic), T3 (6% glycerol with probiotic) and T4 (6% glycerol without probiotic) with four replicates of 15 chicks, each of 45.8±0.23 g body weight. Results indicated that, the dressed breast weight and its percent was significantly higher in T1 followed by T2 and almost comparable in T3 and T4 as compared to control. LDL was significantly lower in T1 as compared to T0, T2, T3 and T4. The % litter moisture was significantly increased as glycerol inclusion level increased. From the results, it was concluded that 3% glycerol in diet with probiotic significantly improved dressed breast weight, lowered LDL and increased litter moisture with increase in glycerol level.

Metabolism, morphology and transcriptome analysis of oscillatory behavior of Clostridium butyricum during long-term continuous fermentation for 1,3-propanediol production

BackgroundOscillation is a special cell behavior in microorganisms during continuous fermentation, which poses threats to the output stability for industrial productions of biofuels and biochemicals. In previous study, a spontaneous oscillatory behavior was observed in Clostridium butyricum-intensive microbial consortium in continuous fermentation for 1,3-propanediol (1,3-PDO) production from glycerol, which led to the discovery of oscillation in species C. butyricum.ResultsSpontaneous oscillations by C. butyricum tended to occur under glycerol-limited conditions at low dilution rates. At a glycerol feed concentration of 88 g/L and a dilution rate of 0.048 h−1, the oscillatory behavior of C. butyricum was observed after continuous operation for 146 h and was sustained for over 450 h with an average oscillation period of 51 h. During oscillations, microbial glycerol metabolism exhibited dramatic periodic changes, in which productions of lactate, formate and hydrogen significantly lagged behind that of other products including biomass, 1,3-PDO and butyrate. Analysis of extracellular oxidation–reduction potential and intracellular ratio of NAD+/NADH indicated that microbial cells experienced distinct redox changes during oscillations, from oxidized to reduced state with decreasing of growth rate. Meanwhile, C. butyricum S3 exhibited periodic morphological changes during oscillations, with aggregates, elongated shape, spores or cell debris at the trough of biomass production. Transcriptome analysis indicated that expression levels of multiple genes were up-regulated when microbial cells were undergoing stress, including that for pyruvate metabolism, conversion of acetyl-CoA to acetaldehyde as well as stress response.ConclusionThis study for the first time systematically investigated the oscillatory behavior of C. butyricum in aspect of occurrence condition, metabolism, morphology and transcriptome. Based on the experimental results, two hypotheses were put forward to explain the oscillatory behavior: disorder of pyruvate metabolism, and excessive accumulation of acetaldehyde.

Continuous Anaerobic Co-Digestion of Biowaste with Crude Glycerol under Mesophilic Conditions

A persistent topic of the anaerobic digestion of biowaste is the efficient use of co-substrates. According to Renewable Energy Sources Act the co-substrate input is limited to 10 percent of the average daily substrate feed in Germany. In this concern, the primary focus of this paper is to understand the suitability of crude glycerol in anaerobic digestion of biowaste. Two identical lab-scale anaerobic digester units were added with crude glycerol, and each unit was equipped with four identical fermenters. Unit A was fed with an average organic loading rate of 4.5 kg VS m−3 d−1, and the average organic loading rate of unit B was set at 5.5 kg VS m−3 d−1. The share of crude glycerol in the total feed was 0.77 percent of the fresh matter. The abort criterion is a ratio of the volatile organic acids and buffer capacity (FOS/TAC) in the fermenter above 1.2. The abort criterion was reached after 16 days. In summary, the results lead us to the conclusion crude glycerol is not suitable as a co-substrate for anaerobic digestion for several reasons.

Sequential fed-batch fermentation of 1,3-propanediol from glycerol by Clostridium butyricum DL07

The demand for 1,3-propanediol (1,3-PDO) has increased sharply due to its role as a monomer for the synthesis of polytrimethylene terephthalate (PTT). Although Clostridium butyricum is considered to be one of the most promising bioproducers for 1,3-PDO, its low productivity hinders its application on industrial scale because of the longer time needed for anaerobic cultivation. In this study, an excellent C. butyricum (DL07) strain was obtained with high-level titer and productivity of 1,3-PDO, i.e., 104.8g/L and 3.38g/(L•h) vs. 94.2g/L and 3.04g/(L•h) using pure or crude glycerol as substrate in fed-batch fermentation, respectively. Furthermore, a novel sequential fed-batch fermentation was investigated, in which the next bioreactor was inoculated by C. butyricum DL07 cells growing at exponential phase in the prior bioreactor. It could run steadily for at least eight cycles. The average concentration of 1,3-PDO in eight cycles was 85g/L with the average productivity of 3.1g/(L•h). The sequential fed-batch fermentation could achieve semi-continuous production of 1,3-PDO with higher productivity than repeated fed-batch fermentation and would greatly contribute to the industrial production of 1,3-PDO by C. butyricum. KEY POINTS: • A novel C. butyricum strain was screened to produce 104.8g/L 1,3-PDO from glycerol. • Corn steep liquor powder was used as a cheap nitrogen source for 1,3-PDO production. • A sequential fed-batch fermentation process was established for 1,3-PDO production. • An automatic glycerol feeding strategy was applied in the production of 1,3-PDO.

Influence of reaction parameters on glycerol dehydration over HZSM-5 catalyst

HZSM-5 with Si/Al ratio of 25 has been synthesized and applied as a catalyst to the gas-phase dehydration of glycerol. Despite the high conversion and selectivity to acrolein achieved by this zeolite, its deactivation is still an issue. Therefore, successful application of this zeolite depends on deep understanding of how operating conditions affect its behavior. This study aims to investigate how distinct reaction conditions influence conversion and selectivity over time of HZSM-5 with Si/Al ratio of 25. In order to accomplish these objectives, HZSM-5 was synthesized and characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption, temperature-programmed desorption of NH3 and thermogravimetric analysis. The catalyst was tested under different conditions of O2 concentration (0, 10, 15 and 20 V%), temperature (300, 325 and 350 °C), glycerol aqueous solution concentration (10, 15 and 20 wt%) and spatial velocities (1091, 1227 and 1363 h−1). Results showed that the different conditions under evaluation played a key role in the catalyst performance and lifetime. Under the range studied, increasing O2 concentration and temperature, and decreasing glycerol feeding ratio and spatial velocity had positive effect on glycerol conversion. Selection of proper operating conditions enabled the achievement of high glycerol conversion (above 93%) and high selectivity to acrolein (around 79% of the liquid products) over 15 h of reaction.

The Effect of Noble Metal (M: Ir, Pt, Pd) on M/Ce2O3-γ-Al2O3 Catalysts for Hydrogen Production via the Steam Reforming of Glycerol

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H2 for every mole of C3H8O3. In the work presented herein, CeO2–Al2O3 was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N2 adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H2, CO2, CO, CH4) and the determination of the H2/CO and CO/CO2 molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H2, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles.

Biosynthesis of bioactive tamarixetin in recombinant Escherichia coli.

Tamarixetin, a monomethylated derivative of quercetin, has been reported to possess many important biological activities. In the present study, a whole cell biotransformation system was used for regiospecific methylation of quercetin to produce 4'-O-methylated quercetin (tamarixetin) using methyltransferase from Streptomyces sp. KCTC 0041BP in Escherichia coli Bl21 (DE3). Its production was enhanced by adding a plasmid containing S-adenosine-l-methionine (SAM) synthase from E. coli K12 (MetK) with subsequent feeding of l-methionine and glycerol in the culture. The best condition produced ∼279 μM (88.2 mg/L) of tamarixetin. The biological activity of tamarixetin was tested and compared with quercetin, 7-O-methylated quercetin, and 3-O-methylated quercetin. Results showed that the growth of all tested cancer cell lines (AGS, B16F10, C6, and HeLa) were inhibited by tamarixetin more effectively than other methylated derivatives of quercetin or quercetin. Tamarixetin also exhibited the best antimelanogenic activity among all compounds tested.

Allyl alcohol production by gas phase conversion reactions of glycerol over bifunctional hierarchical zeolite-supported bi- and tri-metallic catalysts

The gas-phase conversion of glycerol into allyl alcohol over Fe–Mo and Cs–Fe–Mo/HZSM-5 (with SiO2/Al2O3 = 30 and 1500) zeolite catalysts in a packed-bed continuous flow reactor has been reported for the first time. To the best of our knowledge, the Cs–Fe–Mo/HZSM-5 catalyst appears to be most promising for gas-phase conversion of glycerol into allyl alcohol. The structure and catalytic performance for the glycerol conversion over bi- and tri-metallic-promoted zeolite catalysts were studied. The synthesized catalysts were characterized by ICP–AES, ICP–MS, N2 physisorption, SEM, STEM–EDX, XRD, NH3–TPD, CO2–TPD, XPS, TGA and pyridine-DRIFT techniques, which showed that differences in catalysts activity and product distribution are influenced by metal loading, changes of acid-base, and porosity. The most stable allyl alcohol selectivity achieved was 46.1 mol.% at 98.1 mol.% glycerol conversion over the 5wt.%Cs–2.5wt.%Fe–2.5wt.%Mo/HZSM-5 (SiO2/Al2O3 = 1500) catalyst achieved with 10 wt% glycerol feed at 350 °C reaction temperature after 26 h time-on-stream. The superior performance of the synthesized catalyst was attributed to the presence of the basic sites, high mesopore volume and mesopore surface area, balance between acidic-basic sites, synergetic interaction between metal species and ZSM-5 zeolite support. The reaction pathway mechanisms of glycerol to value-added allyl alcohol via the direct glycerol dehydration and hydrogen transfer mechanism over basic sites are proposed.