Decrease In Rate Of Hydrolysis Research Articles

Molecular, Genetic, and Biochemical Characterization of OXA-484 Carbapenemase, a Difficult-to-Detect R214G Variant of OXA-181

OXA-244, an R214G variant of OXA-48, is silently spreading worldwide likely because of difficulties in detection using classical screening media. Here, we characterized two clinical isolates of Escherichia coli and Citrobacter youngae that displayed reduced susceptibility to carbapenems but were lacking significant carbapenemase activity as revealed by negative Carba NP test results. However, positive test results were seen for OXA-48-like enzymes by lateral flow immunoassays. WGS revealed the presence of a blaOXA-181-like gene that codes for OXA-484, an R214G variant of OXA-181. BlaOXA-484 gene was located on a 58.4-kb IncP1-like plasmid (pN-OXA-484), that upon transfer into E. coli HB4 with impaired permeability, conferred carbapenem and temocillin resistance (MICs > 32 mg/L). E. coli TOP10 (pTOPO-OXA-484) revealed reduced MICs in most substrates as compared to E. coli TOP10 (pTOPO-OXA-181), especially for imipenem (0.25 mg/L versus 0.75 mg/L) and temocillin (16 mg/L versus 1028 mg/L). Catalytic efficiencies of OXA-484 were reduced as compared to OXA-181 for most ß-lactams including imipenem and temocillin with 27.5- and 21.7-fold reduction, respectively. Molecular modeling confirmed that the salt bridges between R214, D159, and the R1 substituent’s carboxylate group of temocillin were not possible with G214 in OXA-484, explaining the reduced affinity for temocillin. In addition, changes in active site’s water network may explain the decrease in hydrolysis rate of carbapenems. OXA-484 has weak imipenem and temocillin hydrolytic activities, which may lead to silent spread due to underdetection using selective screening media or biochemical imipenem hydrolysis confirmatory tests.

Molecular, Genetic, and Biochemical Characterization of OXA-484 Carbapenemase, a Difficult-to-Detect R214G Variant of OXA-181

OXA-244, an R214G variant of OXA-48, is silently spreading worldwide likely because of difficulties in detection using classical screening media. Here, we characterized two clinical isolates of Escherichia coli and Citrobacter youngae that displayed reduced susceptibility to carbapenems but were lacking significant carbapenemase activity as revealed by negative Carba NP test results. However, positive test results were seen for OXA-48-like enzymes by lateral flow immunoassays. WGS revealed the presence of a blaOXA-181-like gene that codes for OXA-484, an R214G variant of OXA-181. BlaOXA-484 gene was located on a 58.4-kb IncP1-like plasmid (pN-OXA-484), that upon transfer into E. coli HB4 with impaired permeability, conferred carbapenem and temocillin resistance (MICs > 32 mg/L). E. coli TOP10 (pTOPO-OXA-484) revealed reduced MICs in most substrates as compared to E. coli TOP10 (pTOPO-OXA-181), especially for imipenem (0.25 mg/L versus 0.75 mg/L) and temocillin (16 mg/L versus 1028 mg/L). Catalytic efficiencies of OXA-484 were reduced as compared to OXA-181 for most ß-lactams including imipenem and temocillin with 27.5- and 21.7-fold reduction, respectively. Molecular modeling confirmed that the salt bridges between R214, D159, and the R1 substituent’s carboxylate group of temocillin were not possible with G214 in OXA-484, explaining the reduced affinity for temocillin. In addition, changes in active site’s water network may explain the decrease in hydrolysis rate of carbapenems. OXA-484 has weak imipenem and temocillin hydrolytic activities, which may lead to silent spread due to underdetection using selective screening media or biochemical imipenem hydrolysis confirmatory tests.

Dimethyl Ether Hydrolysis over WO3/γ-Al2O3 Supported Catalysts

Dimethyl ether (DME) is considered an alternative hydrogen carrier with potential use in fuel cells and automotive and domestic applications. Dimethyl ether hydrolysis to methanol is a thermodynamically limited reaction catalyzed by solid-acid catalysts, mainly Al2O3 and zeolites. Moreover, it is the rate-limiting step of the DME steam reforming reaction, which is employed for the production of hydrogen fuel for fuel cell feeding. In the present study, the performance of WO3/Al2O3 catalysts (0–44% wt. WO3) was tested in DME hydrolysis reaction. The catalysts were characterized by means of N2-physisorption, XRD, Raman spectroscopy, XPS, NH3-TPD and 2,6-di-tert-butylpyridine adsorption experiments. The reaction rate of DME hydrolysis exhibited a volcanic trend as a function of tungsten surface density, while the best-performing catalyst was 37WO3/Al2O3, with a tungsten surface density of 7.4 W/nm2, noting that the theoretical monolayer coverage for the specific system is 4–5 W/nm2. Brønsted acidity was directly associated with the catalytic activity, following the same volcanic trend as a function of tungsten surface density. Blocking of Brønsted acid sites with 2,6-di-tert-butylpyridine led to a dramatic decrease in hydrolysis rates by 40 times, proving that Brønsted acid sites are primarily responsible for the catalytic activity. Thus, the type and strength rather than the concentration of acid sites are the key factors influencing the catalytic activity.

Temperature gradient and pH effects on Sor estimates from SWCT tests - The no buffer case

Residual oil saturation (Sor) is the fraction of immobile oil that remains after a water flood. This information is important for calculating recoverable reserves and evaluating EOR campaigns. Single Well Chemical Tracer (SWCT) tests yield a near-well average Sor based on a large rock volume. Correctly performed and analyzed, SWCT tests yield reliable Sor estimates. There are, however, two important effects that commonly are ignored. One is cooling of the reservoir during injection of the cold brine resulting in decreased hydrolysis rate of the primary tracer. The other is the hydrolysis rate's pH dependence. To study these phenomena, we have developed a numerical model of an ethyl acetate SWCT test and applied it to a generic case with test and formation data based on published values. An analytical model is used to calculate how the brine injection temperature varies with time. The ethyl acetate hydrolyses into ethanol and acetic acid that lowers the pH and changes the hydrolysis rate. Any buffer capacity in the injected fluid or formation is neglected. Our model is the first ever to combine realistic temperature calculations with pH dependent ethyl acetate hydrolysis rate during a SWCT test. Sor is estimated from synthetic tracer production curves using the direct chromatographic separation equation as well as the mean residence time. A large number of simulations were performed to investigate how the Sor estimates vary with different model assumptions and input data. In all cases, both methods underestimate the true Sor, typically by 2–4% - in some cases significantly more. We demonstrate that neglecting dispersion in the wellbore during injection and production is warranted with the rock and test data used in this study.

Removal of starch granule-associated proteins affects amyloglucosidase hydrolysis of rice starch granules

Starch granule-associated proteins (SGAPs) include granule-surface proteins (SGSPs) and granule-channel proteins (SGCPs). To investigate impacts of SGAPs on amyloglucosidase (AMG) hydrolysis, waxy and non-waxy rice starches had their SGCPs or SGAPs removed. Removal of SGAPs or SGCPs did not affect morphology and amylopectin chain distribution but decreased relative crystallinity. Removal of SGAPs increased the digestion rate, AMG binding ability and pore diameter of hydrolyzed granules, and accelerated changes in relative crystallinity and destruction of crystalline region on hydrolysis. However, after removing SGCPs, AMG only bound to surface and attacked of the fingerprint of protein bodies on granules, with decreased hydrolysis rate. The degree of change in hydrolysis rate was not determined by SGCPs content of rice starch. These results implied that SGCPs had a more dominant role in AMG hydrolysis of rice starch than did SGSPs. This study provides novel information about the role of SGAPs in AMG hydrolysis mechanisms.

Physical modification of starch: changes in glycemic index, starch fractions, physicochemical and functional properties of heat-moisture treated buckwheat starch.

Native buckwheat starch was extracted and modified by heat-moisture treatment (HMT) with different treatment time (15, 30 and 45min) to investigate its effect on physicochemical, morphological, functional properties, starch profile (rapidly digestible starch, RDS; slowly digestible starch, SDS and resistant starch, RS fractions) and expected glycemic index (eGI). Results revealed that with increasing time duration of HMT from 15 to 45min, amylose content, pasting temperature and thermostability increased substantially whereas swelling power, solubility and viscosity parameters decreased. The SEM micrographs showed that HMT caused fissures in the granule and surface indentation. HMT-45 (starch treated for 45 min) had the lowest RDS content (29.33%) and the highest SDS (51.30%) and RS (8.21%) levels. The decreased hydrolysis rate, high amylose and RS content of HMT-45 resulted in a significant decrease in estimated glycemic index (eGI) values from 51.49% (Native) to 44.16% (HMT-45) thus indicating its role in prevention of non-insulin- dependent diabetes.

How does synthetic musks affect methane production from the anaerobic digestion of waste activated sludge?

The increasing use of synthetic musks has led to a large amount of synthetic musks retaining in waste activated sludge (WAS) via wastewater treatment, thereby entering anaerobic digester. However, the potential effects of synthetic musks on WAS anaerobic digestion remain unknown. Herein, this study selected the dominant galaxolide (HHCB) in WAS as the typical synthetic musks and experimentally evaluated the long-term effects on WAS anaerobic digestion using continuous lab-scale anaerobic digesters as well as the mechanisms involved. The results demonstrated that the increased HHCB levels (i.e., 90, 150 and 200 mg/kg-dw) resulted in the decreased methane production, with the methane production at 200 mg/kg-dw being only 80.5 ± 0.1% of the control. Supporting the methane production data, volatile solids (VS) destruction decreased by 18.6 ± 0.9%, which increased 6.8% of volume waste sludge for transfer and disposal. Correspondingly, the microbial community was shifted in the direction against anaerobic digestion. By modeling based on biochemical methane potential tests and investigating the key stages involved in anaerobic digestion, it was found that although the HHCB showed little impacts on the solubilization, WAS hydrolysis-acidification steps was inhibited by HHCB with the decreased hydrolysis rate and methane production potential, thereby causing the deteriorated performance of WAS anaerobic digestion.

Study on Synthesis and Characterization of Unsaturated Poly (ester-amide) as Bone Fixation Materials

A new type of unsaturated poly ester-amide was prepared by melt polycondensation and characterized completely. Influence of heat treatment conditions and cross-linking content on mechanical and degradation properties of unsaturated polyester-amide were studied. Results suggested that the newly synthesized unsaturated poly(ester-amide) possessed good heat stabilization properties. Mechanical and degradation properties of cross-linked poly (ester-amide) were determined by heat treatment conditions and cross-linker content. Different initiation-accelerating agent systems and their content differences have an insignificant influence on the cross-linking time at Room Temperature (RT). Increasing heat treatment time increased the retention rate of mechanical properties during the degradation process and decreased hydrolysis rate in alkaline solution.

A novel free ammonia based pretreatment technology to enhance anaerobic methane production from primary sludge.

This study proposed a novel free ammonia (FA, i.e., NH3 ) pretreatment technology to enhance anaerobic methane production from primary sludge for the first time. The solubilization of primary sludge was substantially enhanced following 24 h FA pretreatment (250-680 mg NH3 -N/L), by which the release of soluble chemical oxygen demand (SCOD) (i.e., 0.4 mg SCOD/mg VS added; VS: volatile solids) was approximately 10 times as much as that without pretreatment (i.e., 0.03 mg SCOD/mg VS added). Then, biochemical methane potential (BMP) tests demonstrated that FA pretreatment of 250-680 mg NH3 -N/L was capable of enhancing anaerobic methane production while the digestion time was more than 7 days. Model based analysis indicated that the improved anaerobic methane production was due to an increased biochemical methane potential (B0 ) of 8-17% (i.e., from 331 to 357-387 L CH4 /kg VS added), with the highest B0 achieved at 420 mg NH3 -N/L pretreatment. However, FA pretreatment of 250-680 mg NH3 -N/L decreased hydrolysis rate (k) by 24-38% compared with control (i.e., from 0.29 d-1 to 0.18-0.22 d-1 ), which explained the lower methane production over the first 7 days' digestion period. Economic analysis and environmental evaluation demonstrated that FA pretreatment technology was environmentally friendly and economically favorable. Biotechnol. Bioeng. 2017;114: 2245-2252. © 2017 Wiley Periodicals, Inc.

Does sugar inhibition explain mixing effects in enzymatic hydrolysis of lignocellulose?

AbstractBACKGROUNDEnzymatic hydrolysis of lignocellulose is associated with mixing issues, which are likely to affect process performance. The aim of this study was to investigate how viscosity and sugar inhibition influence the mixing‐dependence in hydrolysis of steam‐pretreated spruce.RESULTSThe effect of agitation on low‐viscosity, low‐solid hydrolysis (5% water insoluble solid (WIS)) was marginal, as the conversion after 72 h decreased by 9% when decreasing the agitation rate from 600 to 100 rpm. However, when the viscosity at 5% WIS was increased by Xanthan addition, the effect of agitation was greater, and conversion decreased by 21% when decreasing agitation from 600 to 100 rpm. For high‐viscosity, high‐solid hydrolysis (16% WIS), the conversion decreased by 54% when decreasing the agitation from 600 to 100 rpm. However, when the product concentration was kept low by simultaneous saccharification and fermentation (SSF), the effect of agitation was weaker, and conversion decreased by only 14%.CONCLUSIONThe results of this study strongly suggest that poor mixing in viscous lignocellulose hydrolysis causes local product accumulation, leading to increased inhibition and decreased hydrolysis rates. Decreasing the glucose and cellobiose concentration removes the mixing‐dependence, highlighting SSF as an attractive option for large‐scale hydrolysis and fermentation of steam‐pretreated softwood. © 2016 Society of Chemical Industry

Lactose hydrolysis potential and thermal stability of commercial β-galactosidase in UHT and skimmed milk

The commercial enzyme (E.C. = 3.2.1.23) from Kluyveromyces lactis (liquid) and Aspergillus oryzae(lyophilized) was investigated for its hydrolysis potential in lactose substrate, UHT milk, and skimmed milk at different concentrations (0.7; 1.0 and 1.5%), pH values (5.0; 6.0; 6.5 and 7.0), and temperature (30; 35; 40 and 55 oC). High hydrolysis rates were observed for the enzyme from K. lactis at pH 7.0 and 40 oC, and from A. oryzae at pH 5.0 and 55 oC. The enzyme from K. lactis showed significantly higher hydrolysis rates when compared to A. oryzae. The effect of temperature and β-galactosidase concentration on the lactose hydrolysis in UHT milk was higher than in skimmed milk, for all temperatures tested. With respect to the thermal stability, a decrease in hydrolysis rate was observed at pH 6.0 at 35 oC for K. lactisenzyme, and at pH 6.0 at 55 oC for the enzyme from A. oryzae. This study investigate the hydrolysis of β-galactosidase in UHT and skimmed milk. The knowledge about the characteristics of the β-galactosidase fromK. lactis and A. oryzae enables to use it most efficiently to control the enzyme concentration, temperature, and pH in many industrial processes and product formulations.

Determination of the Influence of Substrate Concentration on Enzyme Selectivity Using Whey Protein Isolate and Bacillus licheniformis Protease

Increasing substrate concentration during enzymatic protein hydrolysis results in a decrease in hydrolysis rate. To test if changes in the mechanism of hydrolysis also occur, the enzyme selectivity was determined. The selectivity is defined quantitatively as the relative rate of hydrolysis of each cleavage site in the protein. It was determined from the identification and quantification of the peptides present in the hydrolysates. Solutions of 0.1-10% (w/v) whey protein isolate (WPI) were hydrolyzed by Bacillus licheniformis protease at constant enzyme-to-substrate ratio. The cleavage sites were divided into five groups, from very high (>10%) to very low selectivity (<0.1%). The selectivity toward cleavage sites after Glu 62 and 134 was 2 times higher at 10% (w/v) WPI than at the lower protein concentrations. This finding shows that both the rate of hydrolysis and the enzyme selectivity were influenced by the substrate concentration.

Factors impeding enzymatic wheat gluten hydrolysis at high solid concentrations

Enzymatic wheat gluten hydrolysis at high solid concentrations is advantageous from an environmental and economic point of view. However, increased wheat gluten concentrations result in a concentration effect with a decreased hydrolysis rate at constant enzyme-to-substrate ratios and a decreased maximum attainable degree of hydrolysis (DH%). We here identified the underlying factors causing the concentration effect. Wheat gluten was hydrolyzed at solid concentrations from 4.4% to 70%. The decreased hydrolysis rate was present at all solid concentrations and at any time of the reaction. Mass transfer limitations, enzyme inhibition and water activity were shown to not cause this hydrolysis rate limitation up to 50% solids. However, the hydrolysis rate limitation can be, at least partly, explained by a second-order enzyme inactivation process. Furthermore, mass transfer impeded the hydrolysis above 60% solids. Addition of enzyme after 24 h at high solid concentrations scarcely increased the DH%, suggesting that the maximum attainable DH% decreases at high solid concentrations. Reduced enzyme activities caused by low water activities can explain this DH% limitation. Finally, a possible influence of the plastein reaction on the DH% limitation is discussed.

Pretreatment and enzymatic hydrolysis of wheat straw (Triticum aestivum L.) – The impact of lignin relocation and plant tissues on enzymatic accessibility

Wheat straw is a potential feedstock for bioethanol production. This paper investigates tissues from whole internode sections subjected to hydrothermal pretreatment at 185°C and subsequent enzymatic hydrolysis up to 144 h. Analyses revealed an increase in surface lignin as hydrolysis progressed, which could be coupled to the gradual decrease in hydrolysis rate over time. The data support the hypothesis of lignin extraction from the cell wall matrix during pretreatment and deposition as droplets upon cooling. These droplets are assumed to accumulate during enzymatic hydrolysis. Additionally, after 144 h of enzymatic hydrolysis the cortex had vanished, exposing the heavier lignified vascular tissue. Accumulation of lignin droplets and exposure of residual lignin could be part of the explanation for the decreasing hydrolysis rate. Flattening of macrofibrils after pretreatment together with more indentations on the surfaces was also observed, possibly caused by a proposed synergistic effect of cellobiohydrolases and endoglucanases.

A mechanistic model of the enzymatic hydrolysis of cellulose

A detailed mechanistic model of enzymatic cellulose hydrolysis has been developed. The behavior of individual cellulase enzymes and parameters describing the cellulose surface properties are included. Results obtained for individual enzymes (T. reesei endoglucanase 2 and cellobiohydrolase I) and systems with both enzymes present are compared with experimental literature data. The model was sensitive to cellulase-accessible surface area; the EG2-CBHI synergy observed experimentally was only predicted at a sufficiently high cellulose surface area. Enzyme crowding, which is more apparent at low surface areas, resulted in differences between predicted and experimental rates of hydrolysis. Model predictions also indicated that the observed decrease in hydrolysis rates following the initial rate of rapid hydrolysis is not solely caused by product inhibition and/or thermal deactivation. Surface heterogeneities, which are not accounted for in this work, may play a role in decreasing the hydrolysis rate. The importance of separating the enzyme adsorption and complexation steps is illustrated by the model's sensitivity to the rate of formation of enzyme-substrate complexes on the cellulose surface.

In vitro and in vivo degradation behaviors of thermosensitive poly(organophosphazene) hydrogels

Biodegradable and thermosensitive poly(organophosphazenes) with various substituents were synthesized and their hydrolytic degradation properties were investigated in vitro and in vivo. The aqueous solutions of all polymers showed a sol–gel phase transition behavior depending on temperature changes. The side groups of polymers significantly affected the polymer degradation and accelerated hydrolysis of polymers in the order of carboxylic acid > depsipeptide > without carboxylic acid and depsipeptide. The increased gel strength led to the decreased hydrolysis rate. The polymer hydrogels with 750 Da of α-amino-ω-methoxy poly(ethylene glycol) were rapidly decreased by dissolution. The polymer degradation was also influenced by pH and temperature. The in vivo behaviors of mass decrease of the polymer hydrogels were similar with the in vitro results. These results suggest that the biodegradable and thermosensitive poly(organophosphazenes) hold great potentials as an injectable and biodegradable hydrogel for biomedical applications with controllable degradation rate.

Myosin-catalyzed ATP hydrolysis elucidated by 31P NMR kinetic studies and 1H PFG-diffusion measurements

We conducted (31)P NMR kinetic studies and (1)H-diffusion measurements on myosin-catalyzed hydrolysis of adenosine triphosphate (ATP) under varied conditions. The data elucidate well the overall hydrolysis rate and various factors that significantly impact the reaction. We found that the enzymatic hydrolysis of ATP to adenosine diphosphate (ADP) was followed by ADP hydrolysis, and different nucleotides such as ADP and guanosine triphosphate acted as competitors of ATP. Increasing ATP or Mg(2+) concentration resulted in decreased hydrolysis rate, and such effect can be related to the decrease of ATP diffusion constants. Below 50 degrees C, the hydrolysis was accelerated by increasing temperature following the Arrhenius' law, but the hydrolysis rate was significantly lowered at higher temperature (approximately 60 degrees C), due to the thermal-denaturation of myosin. The optimal pH range was around pH 6-8. These results are important for characterization of myosin-catalyzed ATP hydrolysis, and the method is also applicable to other enzymatic nucleotide reactions.

Dihydroartemisinin-cyclodextrin complexation: Solubility and stability

Dihydroartemisinin (DHA) is a major metabolite of artemisinin and its derivatives, including arteether, artemether, and artesunate. To improve the solubility and stability of poorly soluble DHA, we prepared inclusion complexes with hydroxypropyl-beta-cyclodextrin (HPbetaCD) and recrystalized DHA to study its thermal stability. The complexes were characterized by differential scanning calorimetery (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction patterns (XRD), thermal stability, phase, and equilibrium solubility studies. Pure DHA was crystalline and remained crystalline after recrystallization, but its unit cell dimensions changed as exhibited by XRD. DHA-HPbetaCD complexes showed a phase transitions towards amorphous in DSC thermograms, FTIR spectra, and XRD patterns. The phase solubility profiles of complexes prepared in water, acetate buffer, and phosphate buffers were classified as A(L)-type, indicating the formation of a 1:1 stoichiometric inclusion complex. The equilibrium solubility of DHA was enhanced as a function of HPbetaCD concentration. DHA-HPbetaCD complexes showed an 89-fold increase in solubility compared to DHA. Solubilities of complexes containing 275.1 mM HPbetaCD in water, acetate buffer (pH 3.0), and phosphate buffer (pH 3.0 and 7.4) were 10.04, 7.96, 6.30, and 11.61 mg/ml, respectively. Hydrogen bonding was found between DHA and HPbetaCD, and it was stronger in complexes prepared in water than in buffers. However, the AH values were higher in buffer than water. DHA-HPbetaCD complexes prepared using commercial (untreated) or recrystallized DHA (no detectable impurity) showed a 40% increase in thermal stability (50 degrees C) and a 29-fold decrease in hydrolysis rates compared with DHA. The rank order of stability constants (K(s)) was: water, acetate buffer (pH 3.0), phosphate buffer (pH 3.0), and phosphate buffer (pH 7.4). Thus, HPbetaCD complexation with recrystalized DHA increases DHA solubility and stability.

Importance of Protease Cleavage Sites within and Flanking Human Immunodeficiency Virus Type 1 Transframe Protein p6* for Spatiotemporal Regulation of Protease Activation

The human immunodeficiency virus type 1 (HIV-1) protease (PR) has recently been shown to be inhibited by its propeptide p6* in vitro. As p6* itself is a PR substrate, the primary goal of this study was to determine the importance of p6* cleavage for HIV-1 maturation and infectivity. For that purpose, short peptide variants mimicking proposed cleavage sites within and flanking p6* were designed and analyzed for qualitative and quantitative hydrolysis in vitro. Proviral clones comprising the selected cleavage site mutations were established and analyzed for Gag and Pol processing, virus maturation, and infectivity in cultured cells. Amino-terminal cleavage site mutation caused aberrant processing of nucleocapsid proteins and delayed replication kinetics. Blocking the internal cleavage site resulted in the utilization of a flanking site at a significantly decreased hydrolysis rate in vitro, which however did not affect Gag-Pol processing and viral replication. Although mutations blocking cleavage at the p6* carboxyl terminus yielded noninfectious virions exhibiting severe Gag processing defects, mutations retarding hydrolysis of this cleavage site neither seemed to impact viral infectivity and propagation in cultured cells nor seemed to interfere with overall maturation of released viruses. Interestingly, these mutants were shown to be clearly disadvantaged when challenged with wild-type virus in a dual competition assay. In sum, we conclude that p6* cleavage is absolutely essential to allow complete activation of the PR and subsequent processing of the viral precursors.

Polyamide Synthesis from 6‐Aminocapronitrile, Part 1: N‐Alkyl Amide Formation by Amine Amidation of a Hydrolyzed Nitrile

The synthesis of N-hexylpentanamide from a stoichiometric amount of pentanenitrile and hexylamine has been studied as a model reaction for the synthesis of nylon-6 from 6-aminocapronitrile. The reaction was carried out under mild hydrothermal conditions and in the presence of a homogeneous ruthenium catalyst. For the mild hydrothermal conditions the presence of hexylamine distinctively increases the nitrile hydrolysis compared to the nitrile hydrolysis in the absence of hexylamine. Amine-catalyzed nitrile hydrolysis mainly produces the N-substituted amide. A clear product development is observed, consisting of first the terminal amide formation and second the accumulation of N-hexylpentanamide. With a maximum conversion of only 80 % after 18 h, the nitrile hydrolysis rate at 230 degrees C is still much too low for nylon-6 synthesis. Ruthenium dihydride phosphine was therefore used as a homogeneous catalyst, which significantly increases the nitrile hydrolysis rate. At a temperature of 140 degrees C and with only 0.5 mol % [RuH(2)(PPh(3))(4)] a 60 % nitrile conversion is already reached within 2 h. Initially the terminal amide is the sole product, which is gradually converted into N-hexylpentanamide. The reaction has a high initial rate, however, for higher conversions a strong decrease in hydrolysis rate is observed. This is ascribed to product inhibition, which results from the equilibrium nature of the reaction.