Toxic effects of acrylic acid on Clostridium propionicum and isolation of acrylic acid‐tolerant mutants for production of acrylic acid

This work presents a systematic investigation of the toxic effects of acrylic acid on the growth of Clostridium propionicum and the isolation of acrylic acid‐tolerant mutants. The results suggest that addition of acrylic acid prolonged the lag phase of the fermentation and reduced the initial‐specific growth rate, as well as the final cell concentration. Moreover, the toxic effect of acrylic acid was sensitive to the pH value. The minimal inhibition concentration of acrylic acid increased from 1.11 to 31.25 mM when the pH value rose from 5.8 to 7.4. In addition, the molar concentration ratio of products (acetic acid:propionic acid) was enhanced with the supplementation of acrylic acid. The highest ratio was 0.7:1 when acrylic acid was 20.83 mM at pH 7.4. Two acrylic acid‐tolerant mutants were isolated, which could still grow at a high concentration (43.06 mM) of acrylic acid. These strains could be instrumental for improved bioproduction of acrylic acid.     

Hydrogel composed of acrylic coumarin and acrylic Pluronic F-127 and its photo- and thermo-responsive release property

Hydrogels comprising acrylic coumarin (AC) and acrylic Pluronic F-127 (APF) were prepared by a free radical reaction and its photo- and thermal-responsive release property was investigated using methylene blue as a solute. AC and APF were prepared successfully, confirmed by ¹H NMR spectroscopy. The molar ratio of Pluronic F-127 chain to vinyl group of APF was 1:1.3, suggesting that diacrylic Pluronic F-127 which could act as a cross-linker for the formation of polymer networks was produced. The coumaryl groups of AC were dimerized as much as 60.1% by 2 h-UV irradiation. On the DSC thermogram, APF exhibited its melting point around 55.4°C, about 0.9°C lower than the melting point of Pluronic F-127. The gelling temperature of Pluronic F-127 solution (25% (w/v)) was about 40°C, determined by a viscometric method. The swelling ratio of the hydrogels increased up to greater than 8 in 30 min. The maximum release degree at 23 and 50°C of dye loaded in the hydrogels was suppressed by UV irradiation, possibly because of the photo-dimerization of coumaryl groups. The release degree at 50°C of dye loaded in the UV-treated hydrogels was lower as the content of APF was higher, possibly because the thermally induced gelation of the polymer chains could suppress the payload release from the hydrogels.     

一株产丙烯酸和一株耐高浓度丙烯酸细菌的筛选与鉴定

从广西大学农场、养猪场排水沟、奶牛场的排水沟、屠宰场的废液池及鱼塘的污泥和废水中分离到1株能产丙烯酸和1株耐高浓度丙烯酸的菌株。经高效气相色谱检测其培养提取物,能产丙烯酸的菌株在培养物中丙烯酸的摩尔浓度达到3．5mmoL／L;耐高浓度丙烯酸的菌株其耐受丙烯酸的摩尔浓度可以达到2moL／L,对这2个菌株进行16S rDNA鉴定,它们分别属于Cellulosimicrobium属和Brevundimonas属。     

Bonding acrylic teeth to acrylic resin denture bases: a review

Partial or complete dentures are more commonly constructed for the elderly group of the population. Teeth debonding from the dentures can be frustrating to the patients as well as the dentist. Research has been carried out and is continuing to study the issue of bonding acrylic teeth to the denture base resin. The present review takes into account the majority of research papers published in the last five decades for determining the bond strength. Selection of more compatible combinations of denture base resins and acrylic teeth may reduce the number of prosthesis fractures and the resultant repairs.     

Effect of pre-processing methods on bond strength between acrylic resin teeth and acrylic denture base resin

doi: 10.1111/j.1741‐2358.2011.00480.x
Effect of pre‐processing methods on bond strength between acrylic resin teeth and acrylic denture base resin Objectives: This study evaluated the effects of various pre‐processing methods on the bond strength between resin and denture teeth. Backgrounds: Debonding of acrylic resin teeth from denture base material is a problem for patients wearing complete dentures. Materials and Methods: Four experimental groups (n = 30) were investigated by subjecting tooth–resin bonding to tensile loading. Specimens were prepared and tested according to the methods of the International Standards Organization (ISO 22112:2005) using a special assembly. Four pre‐processing surface treatments of teeth were applied: (i) ST₁, no treatment applied (control); (ii) ST₂, wax solvent (Dewaks, Faber Kimya & Ilaç, Turkey); (iii) ST₃, boiling water followed by conditioning with methyl methacrylate (MMA) monomer (Meliodent, Bayer Dental, Germany); (iv) ST₄, boiling water followed by wax solvent agent and finally MMA monomer application. Bond strength test was performed using a universal testing machine. Results: All the strength values of the test groups were within clinically acceptable limits. The lowest values were from the ST₁ group and the highest values were in the ST₄ group. Conclusions: Wax elimination methods affected bonding strength. Application of wax solvent and MMA monomer to the ridge lap surfaces of the teeth gave the best results. In clinical practice, this application procedure may decrease the bonding failure of denture teeth.     

Bacterial degradation of acrylic oligomers and polymers

Three bacterial strains that assimilate acrylic trimer as a carbon and energy source were isolated from activated sludge and soil samples and were tentatively identified as Microbacterium sp. II-7-12, Xanthomonas maltophilia W1 and Acinetobacter genospecies 11 W2. They could assimilate acrylic monomer, dimer and trimer, but not polymers. Trimer, 0.2%, was completely consumed in 3 days. The culture filtrate became alkaline during bacterial growth. From the values of biological O₂ consumption versus theoretical O₂ consumption towards oligomers and polymers, biodegradation of acrylic polymers by trimer-utilizing bacteria was suggested. The resting cells of three bacteria grown on trimer degraded acrylic polymers (average relative molecular mass of 1000–4500) at a concentration of 100 ppm (0.01%). The biodegradation rate of acrylic polymer by resting cells was calculated to be approximately 1/120 of that of acrylic trimer. Acyl-CoA synthetase activities towards oligomeric or polymeric acrylates were found with cell-free extracts of the three bacteria.     

Enzyme-mediated polymerization of acrylic monomers

Summary Acrylamide, methyl acrylate, hydroxyethyl methacrylate, acrylic acid, and methyl methacrylate polymerize in the presence of various enzymes such as peroxidases, oxidases, etc. and their reaction substrates. The initiation of the polymerization mechanism is attributed to generation of free radicals that results from the enzyme-substrate reactions. The enzyme induced polymerization has been extended to multicomponent polymers.     

Protein complexation with acrylic polyampholytes

The interaction of dilute mixtures of proteins and ABC triblock methacrylic polyampholytes at different values of pH was investigated turbidimetrically. The onset of interaction was manifested by large changes in turbidity at certain critical pHs which lie close to the isoelectric points of the two interacting components. Protein precipitation yields in protein-polyampholyte binary mixtures followed the corresponding turbidity profiles and varied from 10% to 90%. The synthetic polyampholytes self-aggregate around their isoelectric point. The kinetics of precipitation of one of the same polymer with soybean trypsin inhibitor were studied, with turbidity-based characteristic times (exponential fit) of 2-3 min. The kinetics of precipitation of the protein-polymer mixture are slower than that of pure polymer because a small, but steady, long-term increase in turbidity is observed in the former case. The pH-dependence of the turbidity of binary mixtures of one protein and one synthetic polyampholyte, as well as a tertiary mixture of two proteins and one polyampholyte, were measured 30 min after the pH adjustment. The observations in these experiments along with the measured protein precipitation yields in the binary mixtures and the polyampholyte self-aggregation can be used for polymer removal and recycling. The latter constitutes a significant advantage over the use of homopolyelectrolytes which cannot easily be recycled. (c) 1994 John Wiley & Sons, Inc.     

Immobilized pectolytic enzymes on acrylic supports

The paper deals with the pectolytic enzymes immobilization on different acrylic supports, and the application of immobilized preparations in the apple juice pectinization process. The correlation between the protein content (C_p) and specific catalytic activities of immobilized enyzme preparations suggest a specific immobilization process only in the case of PONILEX ASH type acrylic supports. The active immobilization degree on PONILEX ASH type supports of Ultrazym 100 G and technical pectinase extract ranged from 99.80 to 296.40% for the Pectinesterase (PE) activity, and from 101.85 to 252.94% for the chain splitting (CS) activity, proving that the ionic immobilization process is a selective one. The simulated operational stability of the immobilized pectolytic enzymes tested by the PE and CS activity values proves the preservation of enzyme catalytic activity.     

Surface hydrophobicity and adherence of Candida to acrylic surfaces

The relationship between cell surface hydrophobicities and adherence capacities to acrylic surfaces was investigated with seven laboratory strains and eighteen clinical isolates of Candida species. C. albicans was less adherent to acrylic surfaces than were other species and hardly adhered to hexadecane, whereas other strains, which had a high affinity to hexadecane, were more adherent to acrylic surfaces. A correlation was observed between the adherence capacities of Candida species to acrylic surfaces and their cell hydrophobicities. When acrylic plates were coated with human whole saliva, the contact angle of the plate became smaller than that of the nontreated plate and adherence of hydrophobic strains decreased, whereas the adherence of C. albicans was not affected.     

Imparting permanent antimicrobial activity onto viscose and acrylic fabrics

Viscose and acrylic fabrics were aminated to enhance metal chelation of Cu, Zn and Ni for the purpose of imparting fabrics antimicrobial activity against Escherichia coli and Staphylococcus aureus. Fabrics were firstly epoxidized using epichlorohydrin prior amination. Optimization of the reaction conditions, e.g., temperature, medium pH, amine type and metal type and their concentrations, are reported. Aminated fabrics of viscose and acrylic were shown to be viable for chelation with divalent metal cations. The overall results revealed that antibacterial resistance of metalized aminated fabrics that the activity trend of metals is in the order Cu-complex>Zn-complex>Ni-complex with regard to fighting of microorganisms and permanent even after 10 washing. Reaction mechanism of epoxidation, amination and metal chelation of fabrics are offered supported by FT-IR structural study, nitrogen content and atomic absorption spectroscopy.     

Degradation of acrylic copolymers by white-rot fungi

Various water-soluble homopolymers and copolymers of acrylamide (AAm) and acrylic acid (AA) which contained phenolic sites, such as guaiacol, lignin sulfonate (LS) and 3,4-dihydroxybenzoic acid (3,4-DHBA), were tested with regard to their degradability by white-rot fungi. Compared with Phanerochaete chrysosporium, Pleurotus ostreatus caused a significantly higher decrease in the average molecular weight (_w) of most of the copolymers and the homopolymer under the applied culture conditions. However, the _w of poly(guaiacol/AAm) increased significantly during incubation with Pl ostreatus. P. chrysosporium was able to reduce only the _w of the poly(LS/AA) to a significant degree and not that of the other polymers. The mineralization rate of AAm and AA copolymers and terpolymers of AAm, AA and phenolics (LS, 3,4-DHBA, guiacol), which were tested with P. ostreatus and Trametes versicolor, turned out to be low (0.8–3.2%). While the rates of mineralization were similar among all polymers, the decrease in radioactivity from the culture media was higher with the terpolymers bearing phenolic sites. UV spectra of the culture media revealed that the phenolic sites in the terpolymers were significantly degraded by both fungi. Obviously, the degradation of phenolics within the polymer chain caused a higher decrease in _w but did not significantly increase the mineralization rate.     

Tensile fatigue failure of acrylic bone cement

Tensile fatigue tests of acrylic bone cement were conducted under strain control in a wet environment at 37 degrees C. A constant strain rate of 0.02s-1 was used, resulting in physiologic loading frequencies. Comparison of the tensile fatigue data with the results of previous tension-compression fatigue tests indicates that fatigue failure is governed primarily by the maximum cyclic tensile strain. The compressive portion of the loading cycle has little effect on the number of cycles to failure. A new empirically derived equation is introduced to describe the influence of mean strain and strain amplitude on fatigue endurance. The results emphasize the critical role tensile strains may play in cement failure and loosening of total joint replacements.     

Feasibility of acrylic acid production by fermentation

Acrylic acid might become an important target for fermentative production from sugars on bulk industrial scale, as an alternative to its current production from petrochemicals. Metabolic engineering approaches will be required to develop a host microorganism that may enable such a fermentation process. Hypothetical metabolic pathways for insertion into a host organism are discussed. The pathway should have plausible mass and redox balances, plausible biochemistry, and plausible energetics, while giving the theoretically maximum yield of acrylate on glucose without the use of aeration or added electron acceptors. Candidate metabolic pathways that might lead to the theoretically maximum yield proceed via -alanine, methylcitrate, or methylmalonate-CoA. The energetics and enzymology of these pathways, including product excretion, should be studied in more detail to confirm this. Expression of the selected pathway in a host organism will require extensive genetic engineering. A 100,000-tons/year fermentation process for acrylic acid production, including product recovery, was conceptually designed based on the supposition that an efficient host organism for acrylic acid production can indeed be developed. The designed process is economically competitive when compared to the current petrochemical process for acrylic acid. Although the designed process is highly speculative, it provides a clear incentive for development of the required microbial host, especially considering the environmental sustainability of the designed process.     

Immobilization of penicillin acylase on acrylic carriers

Penicillin acylase obtained from E. Coli (E. C. 3.5.1.11) was covalently bound via glutaric aldehyde to acrylic carriers crosslinked with divinylbenzene or ethylene glycol dimethacrylate. The best enzymatic preparation was obtained by using ethyl acrylate/ ethylene glycol dimethacrylate copolymer. 1 cm³ of the carrier bound 6.4 mg of protein, having 72% activity in relation to the native enzyme. The preparation lost only 10% of its initial activity after 100 d of storage at 4°C. A negligible effect of immobilization on the enzyme activity at different temperatures or pH as well as significant increase of the stability of the immobilized enzyme at elevated temperatures were observed.Abbreviations BA butyl acrylate - AE ethyl acrylate - PA penicillin acylase - 6-APA 6-aminopenicillanic acid - EGDMA ethylene glycol dimethacrylate - DVB divinylbenzene     

Polymerisation stress modelling in acrylic bone cement

Fatigue failure of the cement mantle has been proposed as one of the failure processes contributing to aseptic loosening of cemented joint replacements. It has also been suggested that fatigue failure is dramatically accelerated by residual stress generated during the cement polymerisation process. Previous computational models of the polymerisation process have investigated only the latter part of polymerisation by assuming both instantaneous hardening of the material (a stress locking point) and that all residual stress results from thermal shrinkage after this stress locking point. In this study, finite element models which use the local degree of polymerisation to calculate material properties and shrinkage have been used to predict residual stresses in two models of total hip replacement cement mantles. Results indicate that the final value of cement mantle stress may not be the highest stresses that the cement is subjected to during the polymerisation process. Two models are presented, a 2-dimensional model, which was adapted from a similar model in the literature (Lennon and Prendergast, 2002) and a 3-dimensional concentric-cylinders model. In both cases a chemical kinetics model was used to predict the progress of the polymerisation reaction and a second linear model used to predict cement mechanical properties and density, and so stress generation and volume change, over time. There was good agreement of the results of the 2D model with its counterpart in the literature. For the 3D model, the final residual stress magnitudes and patterns showed good agreement with similar physical and computational models in the literature.     

Chemo-enzymatic synthesis and characterization of graft copolymers from lignin and acrylic compounds

Chemo-enzymatic initiation of graft copolymerization of acrylic compounds onto different technical lignosulfonates (LS) was compared to a Fenton-like system (ferrous ion, t-BHP). The enzyme tested was a phenoloxidase laccase (EC 1.10.3.2) from the white rot basidomycete Trametes versicolor. Most applied lignins were successfully grafted, resulting in a polymer yield of more than 90%. The effect of initiator concentration and the lignin/monomer ratio on the yield and M(w) of enzymatically grafted polymers were studied. The homopolymer proportion in the enzymatically produced grafts of Ca-LS and acrylic acid was 5 to 6x lower than those initiated by the Fenton-like reagent; no such differences were observed for Na-LS.     

Inhibitory effects and biotransformation of acrylic acid in computer-controlled pH-stat CSTRs

In this study, the inhibitory effects and anaerobic biotransformation of acrylic acid in computer-controlled pH-stat completely stirred tank reactors (CSTRs) with two different cultures, namely unacclimated and acrylate-acclimated acetate-enriched Methanosarcina and homogenized (crushed) granular cultures, were investigated. The microbial acclimation, influent concentration, and loading rate of acrylic acid were studied in the experiments. The experimental results revealed that methanogenic cultures at a concentration of 3200 +/- 80 mg/L as volatile suspended solids (VSS) could be acclimated to acrylic acid up to a loading rate of 220 mg/L per day (0.068 g acrylic acid/g VSS per day) in the presence of a constant acetate concentration of 2000 +/- 200 mg/L as the primary substrate after 300 days of acclimation. The same cultures (680 +/- 80 mg/L as VSS), after 80 days of acclimation to acrylic acid as the sole carbon source, transformed acrylic acid up to the loading rate of about 200 mg/L per day (0.29 g acrylic acid/g VSS per day) almost completely (>99%) to acetic and propionic acid, but could not effectively metabolize these intermediate products. Acrylate-acclimated homogenized granular cultures (6900 +/- 80 mg/L as VSS) effectively metabolized 2200 mg/L per day (0.32 g acrylic acid/g VSS per day) of acrylic acid, as the sole carbon source, after 50 days of severe inhibition.