Green Oxidation of Steroids in Nano-Reactors Assembled from Laccase and Linear-Dendritic Copolymers, Polymer Biocatalysis and Biomaterials II (original) (raw)
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Green Oxidation of Steroids in Nanoreactors Assembled from Laccase and Linear-Dendritic Copolymers
ACS Symposium Series, 2008
This chapter describes our recent advances on the utilization of polymer-modified laccase complexes in aqueous systems towards the oxidation/polymerization of naturally hydro phobic steroidal compounds, Equilin (EQ) and 17-β-estradiol (β-EST). We elucidate the kinetic and synthetic aspects of the process with the model compound 5,6,7,8-tetrahydro-2naphthol (ΤΗΝ). The nano-reactor system is composed of linear poly(ethylene oxide)-dendritic poly(benzyl ether) diblock copolymer (G3-PEO13k) and laccase isolated from Trametes versicolor. Other advantages of the complex in comparison to the native enzyme are its recyclability, enhanced stability, activity, and overall simplicity in product harvesting and isolation. A principle of action of the complex is suggested based on these findings and is further supported by the biphasic solid-liquid nature of the reaction medium, which exhibits continuous influx of starting material and steady solid product expulsion. Comparative experiments with linear-linear poly(styrene)-block-poly(ethylene oxide) copoly mer under identical conditions do not evince formation of a 110
Biomacromolecules, 2008
We describe the construction of enzymatic nanoreactors through noncovalent envelopment of a glycoprotein by amphiphilic linear-dendritic AB or ABA copolymers. The synthetic procedure is based on the regioselective adsorption of dendritic poly(benzyl ether)-block-linear poly(ethylene glycol)-block-dendritic poly(benzyl ether) or linear poly(ethylene oxide)-block-dendritic poly(benzyl ether) copolymers onto the oxidative enzyme laccase from Trametes Versicolor in aqueous medium. The complexes formed have improved catalytic activity compared with the native enzyme (77-85 nkat/mL vs 60 nkat/mL, respectively) and are more stable at elevated temperatures up to 70°C. Experiments with deglycosylated laccase confirm that the glycoside fragments in the native enzyme serve as the anchor sites for the linear-dendritic copolymers. The enzymatic nanoreactors are able to effectively oxidize series of substrates: phenolic compounds (syringaldazine) and hydrophobic polyaromatic hydrocarbons (anthracene and benzo[a]pyrene) under "green" chemistry conditions.
Enzymatic bioreactors for the oxidation of estrogenic and anti-inflammatory compounds by laccases
2013
ix 5.3.2. Identification of laccase-catalyzed transformation products of DCF and proposed reaction pathways 5.4. Conclusions Chapter 6. Development and application of laccase-immobilized microreactors: exploring an emerging technology 6.1. Introduction 6.2 Materials and methods 6.2.1. Materials, chemicals and enzyme 6.2.2. Preparation of laccase-immobilized microreactors 6.2.2.1. Effect of the cross-linkers concentration on the laccase immobilization 6.2.3. Protein estimation by amino acid analysis 6.2.4. Continuous laccase activity assay 6.3. Results and discussion 6.3.1. Preparation of laccase-immobilized microreactors 6.3.1.1. Optimum conditions for the immobilization 6.3.2. Biochemical characterization of laccase-immobilized microreactors 6.3.3. Continuous flow kinetics of laccase-immobilized microreactors 6.3.4. Application of laccase-immobilized microreactors 6.3.4.1. Continuous transformation of estrogenic compounds 6.3.4.2. Continuous transformation of anti-inflammatory compounds 6.4. Conclusions 6.5. Acknowledgements General conclusions Conclusiones generals Conclusións xerais References
Biotechnology Progress, 2011
Laccase from Myceliophthora thermophila was immobilized by encapsulation in a sol-gel matrix based on methyltrimethoxysilane and tetramethoxysilane. The amount of laccase used for the preparation of the hydrogel was in the range 2.2-22 mg of protein/mL sol and the corresponding enzymatic activities were in the range 5.5-17.0 U/g biocatalyst. The kinetic parameters of the encapsulated laccase showed that the immobilized enzyme presented lower affinity for the substrate 2,2 0 -azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS). However, the stability of laccase was significantly enhanced after immobilization; thus, both pH and thermal stability improved about 10-30% and tolerance to different inactivating agents (NaN 3 , ZnCl 2 , CoCl 2 , CaCl 2 , methanol, and acetone) was 20-40% higher. The reusability of the immobilized laccase was demonstrated in the oxidation of ABTS for several consecutive cycles, preserving 80% of the initial laccase activity after 10 cycles. The feasibility of the immobilized biocatalyst was tested for the continuous elimination of Acid Green 27 dye as a model compound in a packed-bed reactor (PBR). Removals of 70, 58, 57, and 55% were achieved after four consecutive cycles with limited adsorption on the support: only 10-15%. Finally, both batch stirred tank reactor (BSTR) operated in several cycles and PBR, containing the solid biocatalyst were applied for the treatment of a solution containing the endocrine disrupting chemicals (EDCs): estrone (E1), 17b-estradiol (E2), and 17a-ethinylestradiol (EE2). Eliminations of EDCs in the BSTR were higher than 85% and the reusability of the biocatalyst for the degradation of those estrogens was demonstrated. In the continuous operation of the PBR, E1 was degraded by 55% and E2 and EE2 were removed up to 75 and 60%, at steady-state conditions. In addition, a 63% decrease in estrogenic activity was detected.
Recent Highlights in Green Oxidative Chemical Processes Applied to Steroid Chemistry
InTech eBooks, 2016
Steroids and their oxidation products are widely distributed in living organisms and are important intermediates for the synthesis of many biologically active molecules. Due to their pharmacological and synthetic relevance, several oxidative chemical processes for the functionalization of the steroid nucleus have been developed. Green chemistry principles have been incorporated in some oxidative transformations of steroids, allowing significant advances in synthetic chemistry applied to these compounds. This chapter presents a selection of relevant applications of pharmaceutical green chemistry to steroid's oxidative processes. Special emphasis is given to catalytic processes encompassing heterogeneous nanocatalysts, whose application in this context is increasing over the past years. This chapter is organized according to the reaction type that includes alcohol oxidation, epoxidation of alkenes, and allylic oxidation of alkenes to enones, among other relevant oxidative transformations. Biocatalytic oxidative methods applied to steroid synthesis are not included in this review.
Laccase: a green catalyst for the biosynthesis of poly-phenols
Critical reviews in biotechnology, 2017
Laccases (benzene diol: oxidoreductases, EC 1.10.3.2) are able to catalyze the oxidation of various compounds containing phenolic and aniline structures using dissolved oxygen in water. Laccase structural features and catalytic mechanisms focused on the polymerization of aromatic compounds are reported. A description about the most recent research on the biosynthesis of chemicals and polymers is made. Selected applications of this technology are considered as well as the advantages, shortcomings and future needs related with the use of laccases.
ACS Symposium Series, 2005
This chapter describes a novel approach towards enzyme modification which avoids generation or disruption of covalent chemical linkages or genetic intervention. A unique feature of this strategy is that a glycoenzyme, substrates and applicable cofactors are confined within the well-defined nanoporous regions of a regular micelle constructed by an amphiphilic linear-dendritic block copolymer containing water-soluble linear fragments and hydrophobic dendritic blocks. This new construction principle is illustrated with the enzyme laccase from Trametes versicolor. The complexes were shown to be capable of converting the essentially non-substrate veratryl alcohol to veratryl aldehyde. Further, the activity of this laccase complex in aqueous media, enhanced with selected hydrophobic N-hydroxy mediators, provided the expected diquinone products from the essentially insoluble model compound benzo-α-pyrene. Control probes with laccase, mediators and conventional linear-linear copolymers with comparable molecular weight characteristics failed to evince 80
New Biotechnology, 2012
Enzymatic ring-opening copolymerization of 5-benzyloxy-trimethylene carbonate (BTMC) and 1,4-dioxan-2-one (DON) was investigated for the first time. Immobilized porcine pancreas lipase (IPPL) on silica particles was selected to perform the copolymerization. A series of novel biodegradable copolymers with different compositions were characterized by 1 H NMR, 13 C NMR, and GPC. The influences of reaction conditions such as polymerization time and catalyst concentration on the yield and molecular weight of the copolymers were also studied. The copolymerizations of different monomer feed ratios were carried out in bulk at 150°C with 4.5 wt ‰ IPPL as a catalyst for 24 h. With the increase of the BTMC molar feed ratio from 20% to 79%, the M n of the resulting copolymers increased from 5600 to 63400. Water uptake and static contact angle experiments showed that the hydrophilicity of copolymers could be improved with increasing DON content in the copolymers. Moreover, the in vitro drug release rate (ibuprofen as the model drug) of the resulting copolymers also increased along with the DON content in the copolymers.
Laccase-catalyzed degradation of anti-inflammatories and estrogens
Biochemical Engineering Journal, 2010
Pharmaceuticals are regarded as emerging environmental pollutants since many of them are ubiquitous, recalcitrant and biologically active. In this paper, the degradation of several pharmaceuticals such as anti-inflammatory drugs (diclofenac and naproxen) and estrogen hormones (estrone, 17-estradiol, 17␣-ethinylestradiol) was assessed by means of the commercial laccase (Lac) from Myceliophthora thermophila. The influence of different mediators (synthetic and natural) and their concentration on the Lac-based oxidation system were evaluated. Estrogens were completely degraded after only 15 min while the other types of pharmaceuticals presented higher persistence since 1 h of incubation was required for total removal of diclofenac and 8 h to attain up to 60% of naproxen degradation. Among the different natural mediators, syringaldehyde greatly enhanced the action of the Lac, similarly to the synthetic mediator 1-hydroxibenzotriazole (HBT) in the case of estrogens and diclofenac. The other natural mediators presented significantly high efficiency, obtaining removal percentages ranging from 80% to 100% after 24 h of enzymatic reaction.