Synthesis of polycardanol from a renewable resource using a fungal peroxidase from Coprinus cinereus

Development of a Surfactant-Containing Process to Improve the Removal Efficiency of Phenol and Control the Molecular Weight of Synthetic Phenolic Polymers Using Horseradish Peroxidase in an Aqueous System

To reduce phenolic pollutants in the environment, many countries have imposed firm restrictions on industrial wastewater discharge. In addition, the current industrial process of phenolic resin production uses phenol and formaldehyde as the reactants to perform a polycondensation reaction. Due to the toxicity of formaldehyde and phenolic pollutants, the main purpose of this research was to design a green process using horseradish peroxidase (HRP) enzymatic polymerization to remove phenols and to produce formaldehyde-free phenolic polymers. In this study, the optimal reaction conditions, such as reaction temperature, pH, initial phenol concentration and initial ratio of phenol, and H₂O₂, were examined. Then, the parameters of the enzyme kinetics were determined. To solve the restriction of enzyme inactivation, several nonionic surfactants were selected to improve the phenol removal efficiency, and the optimal operation conditions in a surfactant-containing system were also confirmed. Importantly, the molecular weight of the synthetic phenolic polymers could be controlled by adjusting the ratio of phenol and H₂O_2. The content of biphenols in the products was almost undetectable. Collectively, a green chemistry process was proposed in this study and would benefit the treatment of phenol-containing wastewater and the production of formaldehyde-free phenolic resin in the future.

Improving the synthesis of phenolic polymer using Coprinus cinereus peroxidase mutant Phe230Ala

The F230A mutant of Coprinus cinereus peroxidase (CiP), which has a high stability against radical-inactivation, was previously reported. In the present study, the radical-robust F230A mutant was applied to the oxidative polymerization of phenol. The F230A mutant exhibited better polymerization activities than the wild-type CiP in the presence of water-miscible alcohols i.e., methanol, ethanol, and isopropanol despite its lower stability against alcohols. In particular, the F230A mutant showed a higher consumption of phenol (40%) and yielded phenolic polymer of larger molecular weight (8850Da) in a 50% (v/v) isopropanol-buffer mixture compared with the wild-type CiP (2% and 1519Da, respectively). In addition, the wild-type CiP and F230A mutant had no significant differences in enzyme inactivation by physical adsorption on the polymeric products or by heat incubation, and showed comparable kinetic parameters. These results indicate that high radical stability of the F230A mutant and improved solubility of phenolic polymers in alcohol-water cosolvent systems may synergistically contribute to the production of the high molecular weight phenolic polymer.

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

Naturally occurring phenolic sources: monomers and polymers

Phenolic compounds sourced from agro-based feedstock, viz. cashew nut shell liquid, lignin, tannin, palm oil, and coconut shell tar, have come up as sustainable alternatives to petro-based feedstock. This review explores their utility as green polymer feedstock with citation of ~ 600 references.

Cardanol: a green substitute for aromatic oil as a plasticizer in natural rubber

Cardanol grafted natural rubber, prepared at room temperature, is a potential green substitute for carcinogenic aromatic oil plasticized natural rubber.

First example of a lipophilic porphyrin-cardanol hybrid embedded in a cardanol-based micellar nanodispersion

Cardanol is a natural and renewable organic raw material obtained as the major chemical component by vacuum distillation of cashew nut shell liquid. In this work a new sustainable procedure for producing cardanol-based micellar nanodispersions having an embedded lipophilic porphyrin itself peripherally functionalized with cardanol substituents (porphyrin-cardanol hybrid) has been described for the first time. In particular, cardanol acts as the solvent of the cardanol hybrid porphyrin and cholesterol as well as being the main component of the nanodispersions. In this way a "green" micellar nanodispersion, in which a high percentage of the micellar system is derived from renewable "functional" molecules, has been produced.

In vitro analysis of the monolignol coupling mechanism using dehydrogenative polymerization in the presence of peroxidases and controlled feeding ratios of coniferyl and sinapyl alcohol

In this study, dehydrogenative polymers (DHP) were synthesized in vitro through dehydrogenative polymerization using different ratios of coniferyl alcohol (CA) and sinapyl alcohol (SA) (10:0, 8:2, 6:4, 2:8, 0:10), in order to investigate the monolignol coupling mechanism in the presence of horseradish peroxidase (HRP), Coprinus cinereus peroxidase (CiP) or soybean peroxidase (SBP) with H(2)O(2), respectively. The turnover capacities of HRP, CiP and SBP were also measured for coniferyl alcohol (CA) and sinapyl alcohol (SA), and CiP and SBP were found to have the highest turnover capacity for CA and SA, respectively. The yields of HRP-catalyzed DHP (DHP-H) and CiP-catalyzed DHP (DHP-C) were estimated between ca. 7% and 72% based on the original weights of CA/SA in these synthetic conditions. However, a much lower yield of SBP-catalyzed DHP (DHP-S) was produced compared to that of DHP-H and DHP-C. In general, the DHP yields gradually increased as the ratio of CA/SA increased. The average molecular weight of DHP-H also increased with increasing CA/SA ratios, while those of DHP-C and DHP-S were not influenced by the ratios of monolignols. The frequency of β-O-4 linkages in the DHPs decreased with increasing CA/SA ratios, indicating that the formation of β-O-4 linkages during DHP synthesis was influenced by peroxidase type.

A combined approach of experiments and computational docking simulation to the Coprinus cinereus peroxidase-catalyzed oxidative polymerization of alkyl phenols

The characteristics of the oxidative polymerization of alkyl phenol derivatives catalyzed by Coprinus cinereus peroxidase (CIP) were studied qualitatively and quantitatively using a combined approach of experiments and computational docking simulations. As determined by docking study of CIP and alkyl phenols, the binding interaction was found to be important for the determination of substrate specificity. The distant binding and indirect orientation of o-isopropyl phenol and o-tertiary butyl phenol to the catalytic residue (56His) could explain the inability of CIP to polymerize these substrates. Three hydrophobic residues (156Pro, 192Leu, and 230Phe) at the entrance of the binding pocket were also found to be crucial in binding and orientation of alkyl phenols. A two-parameter QSAR equation with the binding distance and the molecular volume of the substrates was proposed and the polymerization yield was accurately predicted by two-parameter QSAR equation.

The development of a thermostable CiP (Coprinus cinereus peroxidase) through in silico design

Protein thermostability is a crucial issue in the practical application of enzymes, such as inorganic synthesis and enzymatic polymerization of phenol derivatives. Much attention has been focused on the enhancement and numerous successes have been achieved through protein engineering methods. Despite fruitful results based on random mutagenesis, it was still necessary to develop a novel strategy that can reduce the time and effort involved in this process. In this study, a rapid and effective strategy is described for increasing the thermal stability of a protein. Instead of random mutagenesis, a rational strategy was adopted to theoretically stabilize the thermo labile residues of a protein using computational methods. Protein residues with high flexibility can be thermo labile due to their large range of movement. Here, residue B factor values were used to identify putatively thermo labile residues and the RosettaDesign program was applied to search for stable sequences. Coprinus cinereus (CiP) heme peroxidase was selected as a model protein for its importance in commercial applications, such as the polymerization of phenolic compounds. Eleven CiP residues with the highest B factor values were chosen as target mutation sites for thermostabilization, and then redesigned using RosettaDesign to identify sequences. Eight mutants based on the redesigns, were produced as functional enzymes and two of these (S323Y and E328D) showed increased thermal stability over the wild-type in addition to conserved catalytic activity. Thus, this strategy can be used as a rapid and effective in silico design tool for obtaining thermostable proteins.

Antineoplastic agents. 556. Isolation and structure of Coprinastatin 1 from Coprinus cinereus

Cancer cell line bioassay-guided separation of an ethyl acetate extract prepared from a plant-associated fungus, Coprinus cinereus, led to the isolation of three new sesquiterpenes, coprinastatin 1 (1), coprinol (2), and the epimer (4a), of the known sesquiterpene triol (4b). The previously described sesquiterpene 3 and oxazolinone 5 were also isolated. The structure and relative configuration of coprinastatin 1 (1) were determined by HRMS and by 1D- and 2D-NMR spectroscopic analyses. The structure of terpene 2 was elucidated by single-crystal X-ray diffraction experiments. The remaining structures were similarly determined, structure 3 by spectroscopic analyses and both 4a and 5 by X-ray crystal structure determination. Coprinastatin 1 (1) was found to inhibit growth of the murine P388 lymphocytic leukemia cell line and the pathogenic bacterium Neisseria gonorrhoeae.

Detoxification of model phenolic compounds in lignocellulosic hydrolysates with peroxidase for butanol production from Clostridium beijerinckii

In the present study, we investigated the peroxidase-catalyzed detoxification of model phenolic compounds and evaluated the inhibitory effects of the detoxified solution on butanol production by Clostridium beijerinckii National Collection of Industrial and Marine Bacteria Ltd. 8052. The six phenolic compounds, p-coumaric acid, ferulic acid, 4-hydroxybenzoic acid, vanillic acid, syringaldehyde, and vanillin, were selected as model fermentation inhibitors generated during pretreatment and hydrolysis of lignocellulose. The enzyme reaction was optimized as a function of the reaction conditions of pH, peroxidase concentration, and hydrogen peroxide to substrate ratio. Most of the tested phenolics have a broad optimum pH range of 6.0 to 9. Removal efficiency increased with the molar ratio of H(2)O(2) to each compound up to 0.5-1.25. In the case of p-coumaric acid, ferulic acid, vanillic acid, and vanillin, the removal efficiency was almost 100% with only 0.01 microM of enzyme. The tested phenolic compounds (1 g/L) inhibited cell growth by 64-74%, while completely inhibiting the production of butanol. Although syringaldehyde and vanillin were less toxic on cell growth, the level of inhibition on the butanol production was quite different. The detoxified solution remarkably improved cell growth and surprisingly increased butanol production to the level of the control. Hence, our present study, using peroxidase for the removal of model phenolic compounds, could be applied towards the detoxification of lignocellulosic hydrolysates for butanol fermentation.