scholarly journals Ag2O–MnO2/Graphene Oxide Nanocomposite

2020 ◽  
Author(s):  
Farooq Syed ◽  
Mujeeb Khan ◽  
Mohammed Rafi Shaik ◽  
Mufsir Kuniyil ◽  
M Rafiq Siddiqui ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Specific Activity ◽  
Catalytic Efficiency ◽  
Cost Effective ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Recoverable Catalyst ◽  
Aerial Oxidation ◽  
Milling Method ◽  
State Mixing

In this study, we reported the eco-friendly fabrication of Ag2O–MnO2/GRO nanocomposites by the solid-state mixing of separately prepared GRO and Ag2O–MnO2 NPs using ball milling method, a mechanochemical approach. The prepared material was studied for the catalytic effect of GRO in the system for the aerial oxidation of a variety of alcohols. It was found that the (1%)Ag2O–MnO2/(5 wt.%)GRO nanocatalyst demonstrated a high conversion ability (~100%) and excellent selectivity in the presence of O2 as a clean oxidant. The higher catalytic properties of the nanocomposite were attributed to the presence of GRO, which exhibited extraordinary catalytic properties like improved surface area, excellent chemical compatibility, and stability, as well as the introduction of several defects in the obtained nanocomposite that enhance the catalytic performance. The specific activity of 13.3 mmol·g−1·h−1 is obtained for the catalyst i.e. (1%)Ag2O–MnO2/(5 wt.%)GRO, which is reportedly superior to the various other catalysts previously reported in the literature for the same conversion reaction. Our catalytic strategy was highly selective, producing only desired products with no over-oxygenation to carboxylic acids. The merits of our catalytic methodology were: (a) facile process, (b) inexpensive and clean oxidant, (c) no surfactants or nitrogenous bases were required, (d) mild catalytic conditions, (e) cost-effective recoverable catalyst, (f) complete convertibility, (g) full selectivity, (h) rapid process, and (i) applicable to virtually all types of alcohols. So, these highlights made this catalytic strategy to be highly applicable in the industrial applications for manufacturing of carbonyls. To the best of our knowledge, this was the first study of utilizing Ag2O–MnO2/GRO composite as a catalyst for the oxidation of alcohols, highlighting the catalytic efficiency of GRO.

scholarly journals Synthesis, Characterization, and Relative Study on the Catalytic Activity of Zinc Oxide Nanoparticles Doped MnCO3, –MnO2, and –Mn2O3 Nanocomposites for Aerial Oxidation of Alcohols

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Mohamed E. Assal ◽  
Mufsir Kuniyil ◽  
Mohammed Rafi Shaik ◽  
Mujeeb Khan ◽  
Abdulrahman Al-Warthan ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Surface Area ◽  
Selective Oxidation ◽  
Zinc Oxide Nanoparticles ◽  
Specific Activity ◽  
Catalytic Efficiency ◽  
Catalytic Performance ◽  
Oxide Nanoparticles ◽  
Oxidation Of Alcohols ◽  
Aerial Oxidation

Zinc oxide nanoparticles doped manganese carbonate catalysts [X% ZnOx–MnCO3] (where X = 0–7) were prepared via a facile and straightforward coprecipitation procedure, which upon different calcination treatments yields different manganese oxides, that is, [X% ZnOx–MnO2] and [X% ZnOx–Mn2O3]. A comparative catalytic study was conducted to evaluate the catalytic efficiency between carbonates and oxides for the selective oxidation of secondary alcohols to corresponding ketones using molecular oxygen as a green oxidizing agent without using any additives or bases. The prepared catalysts were characterized by different techniques such as SEM, EDX, XRD, TEM, TGA, BET, and FTIR spectroscopy. The 1% ZnOx–MnCO3 calcined at 300°C exhibited the best catalytic performance and possessed highest surface area, suggesting that the calcination temperature and surface area play a significant role in the alcohol oxidation. The 1% ZnOx–MnCO3 catalyst exhibited superior catalytic performance and selectivity in the aerial oxidation of 1-phenylethanol, where 100% alcohol conversion and more than 99% product selectivity were obtained in only 5 min with superior specific activity (48 mmol·g−1·h−1) and 390.6 turnover frequency (TOF). The specific activity obtained is the highest so far (to the best of our knowledge) compared to the catalysts already reported in the literatures used for the oxidation of 1-phenylethanol. It was found that ZnOx nanoparticles play an essential role in enhancing the catalytic efficiency for the selective oxidation of alcohols. The scope of the oxidation process is extended to different types of alcohols. A variety of primary, benzylic, aliphatic, allylic, and heteroaromatic alcohols were selectively oxidized into their corresponding carbonyls with 100% convertibility without overoxidation to the carboxylic acids under base-free conditions.

scholarly journals Directed Evolution of a Homodimeric Laccase from Cerrena unicolor BBP6 by Random Mutagenesis and In Vivo Assembly

2018 ◽  
Vol 19 (10) ◽  
pp. 2989 ◽  
Author(s):  
Ji Zhang ◽  
Fuying Ma ◽  
Xiaoyu Zhang ◽  
Anli Geng
Keyword(s):  
Directed Evolution ◽  
Laccase Activity ◽  
Catalytic Properties ◽  
Random Mutagenesis ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Subunit Interaction ◽  
Cerrena Unicolor ◽  
Protein Model

Laccases have great potential for industrial applications due to their green catalytic properties and broad substrate specificities, and various studies have attempted to improve the catalytic performance of these enzymes. Here, to the best of our knowledge, we firstly report the directed evolution of a homodimeric laccase from Cerrena unicolor BBP6 fused with α-factor prepro-leader that was engineered through random mutagenesis followed by in vivo assembly in Saccharomyces cerevisiae. Three evolved fusion variants selected from ~3500 clones presented 31- to 37-fold increases in total laccase activity, with better thermostability and broader pH profiles. The evolved α-factor prepro-leader enhanced laccase expression levels by up to 2.4-fold. Protein model analysis of these variants reveals that the beneficial mutations have influences on protein pKa shift, subunit interaction, substrate entrance, and C-terminal function.

scholarly journals Improvement in catalytic activity and thermostability of a GH10 xylanase and its synergistic degradation of biomass with cellulase

2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Shuai You ◽  
Chen Xie ◽  
Rui Ma ◽  
Huo-qing Huang ◽  
Richard Ansah Herman ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Dry Matter ◽  
Specific Activity ◽  
Xylanase Activity ◽  
Catalytic Efficiency ◽  
Catalytic Performance ◽  
Biomass Degradation ◽  
Synergistic Degradation ◽  
Gh10 Xylanase ◽  
Hybrid Enzymes

Abstract Background Xylanase is one of the most extensively used biocatalysts for biomass degradation. However, its low catalytic efficiency and poor thermostability limit its applications. Therefore, improving the properties of xylanases to enable synergistic degradation of lignocellulosic biomass with cellulase is of considerable significance in the field of bioenergy. Results Using fragment replacement, we improved the catalytic performance and thermostability of a GH10 xylanase, XylE. Of the ten hybrid enzymes obtained, seven showed xylanase activity. Substitution of fragments, M3, M6, M9, and their combinations enhanced the catalytic efficiency (by 2.4- to fourfold) as well as the specific activity (by 1.2- to 3.3-fold) of XylE. The hybrids, XylE-M3, XylE-M3/M6, XylE-M3/M9, and XylE-M3/M6/M9, showed enhanced thermostability, as observed by the increase in the T50 (3–4.7 °C) and Tm (1.1–4.7 °C), and extended t1/2 (by 1.8–2.3 h). In addition, the synergistic effect of the mutant xylanase and cellulase on the degradation of mulberry bark showed that treatment with both XylE-M3/M6 and cellulase exhibited the highest synergistic effect. In this case, the degree of synergy reached 1.3, and the reducing sugar production and dry matter reduction increased by 148% and 185%, respectively, compared to treatment with only cellulase. Conclusions This study provides a successful strategy to improve the catalytic properties and thermostability of enzymes. We identified several xylanase candidates for applications in bioenergy and biorefinery. Synergistic degradation experiments elucidated a possible mechanism of cellulase inhibition by xylan and xylo-oligomers.

scholarly journals Enhanced Performance of Immobilized Xylanase/Filter Paper-ase on a Magnetic Chitosan Support

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 966
Author(s):  
Aldo Amaro-Reyes ◽  
Azariel Díaz-Hernández ◽  
Jorge Gracida ◽  
Blanca E. García-Almendárez ◽  
Monserrat Escamilla-García ◽  
...  
Keyword(s):  
Filter Paper ◽  
Catalytic Efficiency ◽  
Cost Effective ◽  
Immobilized Enzymes ◽  
Hydrolytic Activity ◽  
Industrial Applications ◽  
Biochemical Properties ◽  
Free Form ◽  
Cross Linking ◽  
Magnetic Chitosan

Enzyme immobilization on different supports has emerged as an efficient and cost-effective tool to improve their stability and reuse capacity. This work aimed to produce a stable immobilized multienzymatic system of xylanase and filter paper-ase (FPase) onto magnetic chitosan using genipin as a cross-linking agent and to evaluate its biochemical properties and reuse capacity. A mixture of chitosan magnetic nanoparticles, xylanase, and FPase was covalently bonded using genipin. Immobilization yield and efficiency were quantified. The activity of free and immobilized enzymes was quantified at different values of pH, temperature, substrate concentration (Km and Vmax), and reuse cycles. The immobilization yield, immobilization efficiency, and activity recovery were 145.3% ± 3.06%, 14.8% ± 0.81%, and 21.5% ± 0.72%, respectively, measured as the total hydrolytic activity. Immobilization confers resistance to acidic/basic conditions and thermal stability compared to the free form. Immobilization improved 3.5-fold and 78-fold the catalytic efficiency (Kcat/Km) of the xylanase and filter paper-ase activities, while immobilized xylanase and FPase could be reused for 34 min and 43 min, respectively. Cross-linking significantly improved the biochemical properties of immobilized enzymes, combined with their simplicity of reuse due to the paramagnetic property of the support. Multienzyme immobilization technology is an important issue for industrial applications.

scholarly journals Peroxidase from Coleus Forskohlii: Purification and Biochemical Characterization

2020 ◽  
Vol 5 (1) ◽  
pp. 9-20
Author(s):  
Yaaser Q. Almulaiky ◽  
Yaaser Q. Almulaiky
Keyword(s):  
Ion Exchange ◽  
Peroxidase Activity ◽  
Biochemical Characterization ◽  
Specific Activity ◽  
Gel Filtration ◽  
Catalytic Efficiency ◽  
Industrial Applications ◽  
Coleus Forskohlii ◽  
Sds Page ◽  
Optimum Ph

In this study, a peroxidase from new source was purified using ion exchange and gel filtration techniques. The recovery for peroxidase activity was 19% with 11-fold purification and specific activity of 749 unit/mg protein. Purified peroxidase demonstrated a molecular mass of 39 kDa using gel filtration and was confirmed as a single band on SDS-PAGE. The purified peroxidase revealed a broad optimum pH activity at 6.0-6.5 and 50°C temperature. The kinetic parameters for purified peroxidase toward H2O2 and guaiacol as substrates were found to be Km = 3.355, 5.395 mM, Kcat = 99.52, 79.56 s-1 and Vmax =1.531, 1.242 µmole ml-1 min-1, respectively. The catalytic efficiency (kcat/Km) of the purified peroxidase was 14.75 and 29.66 s−1 mM−1 for guaiacol and H2O2, respectively. Peroxidase activity was observed to be enhanced by Cu2+, Co2+, Ni2+ and inhibited in the presence of Sn2+, Al3+, Hg2+, NaN3, EDTA and urea. Characterization showed that peroxidase purified from C. forskohlii has the ability to be used for food industrial applications.

Upgrading of Pyrolysis Bio-Oil to Fuel over Supported Nanomaterials - A Review

2014 ◽  
Vol 625 ◽  
pp. 357-360 ◽  
Author(s):  
Madiha Yasir ◽  
Sujan Chowdhury ◽  
Nurlidia Mansor ◽  
Norani Muti Mohamed ◽  
Yoshimitsu Uemura
Keyword(s):  
Active Sites ◽  
Earth Metal ◽  
Catalytic Efficiency ◽  
Cost Effective ◽  
Active Phase ◽  
Catalytic Performance ◽  
Transportation Fuel ◽  
Support Materials ◽  
Highly Active ◽  
Bio Oil

Upgrading of bio-oil obtained from pyrolysis of biomass is one the most attractive way to produce fuel both in technological and economical aspect. Development of cost-effective, long life and highly active catalyst is a major challenge in this concern. Addition of support material to the nanocatalyst not only increases the life span of the catalyst but also offers more active sites as well as reduces the cost by lowering the amount of active metal used. Moreover, selection of appropriate support favors efficient dispersion of the active phase. The main focus of this review article is to look into the development of supported nanocatalysts in the past few decades, comparing catalytic performance and deactivation rate of catalysts in the upgrading of bio-oil to produce a value-aided and efficient transportation fuel. Overall, appreciable work has been done to improve the hydrodeoxygenation reaction using different nanosized rare earth metal support materials with enhanced catalytic efficiency and finally need to be implemented in industries for upgrading of pyrolysis bio-oil.

scholarly journals Improvement of the Stability and Activity of an LPMO Through Rational Disulfide Bonds Design

2022 ◽  
Vol 9 ◽  
Author(s):  
Xiaoli Zhou ◽  
Zhiqiang Xu ◽  
Yueqiu Li ◽  
Jia He ◽  
Honghui Zhu
Keyword(s):  
Disulfide Bonds ◽  
Specific Activity ◽  
Fold Increase ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Enzyme Engineering ◽  
Wild Type ◽  
Polysaccharide Monooxygenases ◽  
Saccharification Efficiency ◽  
The Stability

Lytic polysaccharide monooxygenases (LPMOs) oxidatively break down the glycosidic bonds of crystalline polysaccharides, significantly improving the saccharification efficiency of recalcitrant biomass, and have broad application prospects in industry. To meet the needs of industrial applications, enzyme engineering is needed to improve the catalytic performance of LPMOs such as enzyme activity and stability. In this study, we engineered the chitin-active CjLPMO10A from Cellvibrio japonicus through a rational disulfide bonds design. Compared with the wild-type, the variant M1 (N78C/H116C) exhibited a 3-fold increase in half-life at 60°C, a 3.5°C higher T5015, and a 7°C rise in the apparent Tm. Furthermore, the resistance of M1 to chemical denaturation was significantly improved. Most importantly, the introduction of the disulfide bond improved the thermal and chemical stability of the enzyme without causing damage to catalytic activity, and M1 showed 1.5 times the specific activity of the wild-type. Our study shows that the stability and activity of LPMOs could be improved simultaneously by selecting suitable engineering sites reasonably, thereby improving the industrial adaptability of the enzymes, which is of great significance for applications.

scholarly journals Efficient Biocatalytic Synthesis of Chiral Intermediate of Pregabalin Using Immobilized Talaromyces thermophilus Lipase

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Xu Ding ◽  
Xiao-Ling Tang ◽  
Ren-Chao Zheng ◽  
Yu-Guo Zheng
Keyword(s):  
Industrial Production ◽  
Kinetic Resolution ◽  
Catalytic Properties ◽  
Immobilized Lipase ◽  
Acid Ethyl Ester ◽  
Catalytic Efficiency ◽  
Hydrolytic Activity ◽  
Industrial Applications ◽  
Repeated Use ◽  
Optimized Conditions

A mutant L206F/P207F/L259F of Talaromyces thermophilus lipase (TTL) exhibited high hydrolytic activity towards 2-carboxyethyl-3-cyano-5-methylhexanoic acid ethyl ester (CNDE) for synthesis of (S)-2-carboxyethyl-3-cyano-5-methylhexanoic acid (S-CCMA), a key chiral intermediate of pregabalin. However, low conversion at high CNDE concentration and unreusability of the free TTL mutant restricted its industrial applications. In this study, the TTL mutant was immobilized onto epoxy resin and its catalytic properties for kinetic resolution of CNDE were investigated. Under the optimized conditions, the immobilized lipase exhibited an increased catalytic efficiency even at a CNDE concentration of 3 M with 49.7% conversion and 95% eep. The conversion retained higher than 46.3% even after 10 times repeated use of the immobilized lipase in n-heptane-water biphasic system. These results demonstrated great potential of the immobilized TTL mutant for industrial production of the chiral intermediate of pregabalin.

scholarly journals Versatile Sulfathiazole-Functionalized Magnetic Nanoparticles as Catalyst in Oxidation and Alkylation Reactions

Catalysts ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 348 ◽  
Author(s):  
Ostovar ◽  
Rodríguez-Padrón ◽  
Saberi ◽  
Balu ◽  
Luque
Keyword(s):  
Magnetic Nanoparticles ◽  
Catalytic Properties ◽  
Surface Modifications ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Catalyst Design ◽  
Magnetic Characteristics ◽  
Microwave Assisted ◽  
Functionalized Magnetic Nanoparticles ◽  
Alkylation Reactions

Catalyst design and surface modifications of magnetic nanoparticles have become attractive strategies in order to optimize catalyzed organic reactions for industrial applications. In this work, silica-coated magnetic nanoparticles with a core-shell type structure were prepared. The obtained material was successfully functionalized with sulfathiazole groups, which can enhance its catalytic features. The material was fully characterized, using a multi-technique approach. The catalytic performance of the as-synthesized material was evaluated in 1) the oxidation of benzyl alcohol to benzaldehyde and 2) the microwave-assisted alkylation of toluene with benzyl chloride. Remarkable conversion and selectivity were obtained for both reactions and a clear improvement of the catalytic properties was observed in comparison with unmodified γ-Fe2O3/SiO2 and γ-Fe2O3. Noticeably, the catalyst displayed outstanding magnetic characteristics which facilitated its recovery and reusability.

scholarly journals Disulfide Bond Engineering of an Endoglucanase from Penicillium verruculosum to Improve Its Thermostability

2019 ◽  
Vol 20 (7) ◽  
pp. 1602 ◽  
Author(s):  
Anna Bashirova ◽  
Subrata Pramanik ◽  
Pavel Volkov ◽  
Aleksandra Rozhkova ◽  
Vitaly Nemashkalov ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Rational Design ◽  
Specific Activity ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Penicillium Verruculosum ◽  
Bulk Chemicals ◽  
Commercial Applications ◽  
The Stability ◽  
Dynamics Simulations

Endoglucanases (EGLs) are important components of multienzyme cocktails used in the production of a wide variety of fine and bulk chemicals from lignocellulosic feedstocks. However, a low thermostability and the loss of catalytic performance of EGLs at industrially required temperatures limit their commercial applications. A structure-based disulfide bond (DSB) engineering was carried out in order to improve the thermostability of EGLII from Penicillium verruculosum. Based on in silico prediction, two improved enzyme variants, S127C-A165C (DSB2) and Y171C-L201C (DSB3), were obtained. Both engineered enzymes displayed a 15–21% increase in specific activity against carboxymethylcellulose and β-glucan compared to the wild-type EGLII (EGLII-wt). After incubation at 70 °C for 2 h, they retained 52–58% of their activity, while EGLII-wt retained only 38% of its activity. At 80 °C, the enzyme-engineered forms retained 15–22% of their activity after 2 h, whereas EGLII-wt was completely inactivated after the same incubation time. Molecular dynamics simulations revealed that the introduced DSB rigidified a global structure of DSB2 and DSB3 variants, thus enhancing their thermostability. In conclusion, this work provides an insight into DSB protein engineering as a potential rational design strategy that might be applicable for improving the stability of other enzymes for industrial applications.

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