Poboljšanje enzimske proizvodnje cefaleksina upotrebom velikih koncentracija supstrata i uklanjanjem produkata reakcije kompleksiranjem in situ

Cephalexin (CEX) was synthesized with 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D(–)-phenylglycine methyl ester (PGME) using immobilized penicillin G acylase from Escherichia coli. It was found that substrate concentration and in situ product could remarkably influence the ratio of synthesis to hydrolysis (S/H) and the efficiency of CEX synthesis. The optimal ratio of enzyme to substrate was 65 IU/mM 7-ADCA. High substrate concentration improved the 7-ADCA conversion from 61 to 81 % in the process without in situ product removal (ISPR), while in the synthetic process with ISPR, high substrate concentration increased the 7-ADCA conversion from 88 to 98 %. CEX was easily separated from CEX/β-naphthol complex and its purity and overall yield were 99 and 70 %, respectively.Primjenom imobilizirane Penicilin-G-acilaze iz bakterije Escherichia coli sintetiziran je cefaleksin (CEX) iz 7-amino-3-deacetoksicefalosporanske kiseline (7-ADCA) i D(-)-fenilglicin-metilnog estera (PGME). Koncentracije supstrata i produkta in situ mogu znatno utjecati na omjer sinteze i hidrolize (S/H) i djelotvornost sinteze cefaleksina. Optimalni omjer enzima i supstrata iznosio je 65 IU/mM 7-ADCA. Velika koncentracija supstrata poboljšala je konverziju 7-ADCA sa 61 na 81 % u procesu bez uklanjanja produkta in situ (ISPR), a s 88 na 98 % u procesu sa ISPR. Cefaleksin je lako uklonjen iz kompleksa CEX/β-naftol, a dobiveni je proizvod imao čistoću od 99 % i ukupni prinos od 70 %

Cloning and co-expression of recombinant N-demethylase B and N-demethylase D genes in Escherichia coli

NdmB and ndmD genes encoding N-demethylase (Ndm) B and NdmD from Pseudomonas putida CBB5 were successfully cloned in pET32a, designated as pET32a-ndmB-His-His-ndmD (pET32a-BHHD) and electroporated into Escherichia coli strain BL21 (DE3). Polymerase chain reaction (PCR), restriction enzyme digestion and DNA sequencing were subsequently employed to confirm the success of the procedure. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed that the estimated molecular weight of NdmB and NdmD co-expressed in recombinant E. coli was 35 and 60 kDa, respectively. A one-step purification of Ndms using a Ni-affinity column resulted in a 10.3-fold purification with 33.6% yield. The enzyme activity of NdmB and NdmD showed that 1000 μmol/L theobromine was completely converted into 7-methylxanthine within 90 min by resting cells containing pBHHD

Enhancement of electrical and thermal properties of graphene by aligned carbon nanotubes

Abstract In order to explore the composite effects of graphene (GR) and carbon nanotubes (CNTs), GR/CNTs aerogels and GR/CNTs coatings were fabricated. Aligned carbon nanotubes (ACNTs) and twining carbon nanotubes (TCNTs) were comparatively examined by integrating them with graphene, which has seldom been studied in detail. Freeze drying was novelly adopted to retain the liquid distribution in GR/CNTs mixture. Fourier Transform Infrared Spectroscopy (FTIR) analysis demonstrated that OH group and carboxylic acid groups were effectively induced onto CNTs via chemical modification. Scanning electron microscopy (SEM) showed that ACNTs achieved better dispersion and homogeneity in graphene than TCNTs. GR/CNTs hybrid composite with various loading of ACNTs or TCNTs were examined by electrical/thermal conductivity tests and practically evaluated for thermal management in LEDs. Results revealed that the electrical and thermal properties of graphene can be dramatically enhanced by the proper addition of ACNTs due to the formation of effective conductive bridges. The GR/ACNTs aerogel with 10 wt% ACNTs attained a high electrical conductivity of 2.08?×?104 S m?1, elevated to 2.76?×?104 S m?1 after annealing treatment. The eco-friendly and low-cost GR/ACNTs coating with 10 wt% ACNTs prominently reduced the operating temperature of LEDs by 8.6 °C, acting as potential thermal management materials in practical applications

Strong Field Enhancement and Unidirectional Scattering Based on Asymmetric Nanoantenna

Dielectric-metal nanostructures have lately emerged as one of the most promising approaches to modulating light at the optical frequency. Their remarkable electric and magnetic resonances give them a one-of-a-kind ability to augment local field enhancements with negligible absorption losses. Here, we propose a hybrid metal-dielectric-metal (MDM) nanoantenna that contains a dimer of three-layers of shell nanoparticles. In addition, we only theoretically and numerically show the optical properties of the hybrid dimer nanoantenna. We found that the nanoantenna sustained unidirectional forward scattering with narrow beamwidth (30.9 deg) and strong scattering intensity (up to 5 times larger than the single MDM particle). Furthermore, when the hybrid asymmetric dimer was excited by the plane wave with different electric polarization directions, our findings revealed that the hybrid nanoantenna boosted the gap’s electric near-field while also supporting unidirectional forward scattering. Finally, we analyzed the hybrid dimer with substrates of different materials. It supported strong electric high-order moments along the z-axis and x-axis in gaps between MDM nanoparticles and between MDM nanoparticles and the Ge substrate, owing to the intense displacement currents inside of the dielectric layer. We found that the local electric field of this MDM hybrid dimer nanoantenna with Ge substrate was well improved and attained 3325 v/m

Enhanced Enzymatic Production of Cephalexin at High Substrate Concentration with in situ Product Removal by Complexation

Cephalexin (CEX) was synthesized with 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D(–)-phenylglycine methyl ester (PGME) using immobilized penicillin G acylase from Escherichia coli. It was found that substrate concentration and in situ product could remarkably influence the ratio of synthesis to hydrolysis (S/H) and the efficiency of CEX synthesis. The optimal ratio of enzyme to substrate was 65 IU/mM 7-ADCA. High substrate concentration improved the 7-ADCA conversion from 61 to 81 % in the process without in situ product removal (ISPR), while in the synthetic process with ISPR, high substrate concentration increased the 7-ADCA conversion from 88 to 98 %. CEX was easily separated from CEX/β-naphthol complex and its purity and overall yield were 99 and 70 %, respectively

Poboljšanje enzimske proizvodnje cefaleksina upotrebom velikih koncentracija supstrata i uklanjanjem produkata reakcije kompleksiranjem in situ

Cephalexin (CEX) was synthesized with 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D(–)-phenylglycine methyl ester (PGME) using immobilized penicillin G acylase from Escherichia coli. It was found that substrate concentration and in situ product could remarkably influence the ratio of synthesis to hydrolysis (S/H) and the efficiency of CEX synthesis. The optimal ratio of enzyme to substrate was 65 IU/mM 7-ADCA. High substrate concentration improved the 7-ADCA conversion from 61 to 81 % in the process without in situ product removal (ISPR), while in the synthetic process with ISPR, high substrate concentration increased the 7-ADCA conversion from 88 to 98 %. CEX was easily separated from CEX/β-naphthol complex and its purity and overall yield were 99 and 70 %, respectively.Primjenom imobilizirane Penicilin-G-acilaze iz bakterije Escherichia coli sintetiziran je cefaleksin (CEX) iz 7-amino-3-deacetoksicefalosporanske kiseline (7-ADCA) i D(-)-fenilglicin-metilnog estera (PGME). Koncentracije supstrata i produkta in situ mogu znatno utjecati na omjer sinteze i hidrolize (S/H) i djelotvornost sinteze cefaleksina. Optimalni omjer enzima i supstrata iznosio je 65 IU/mM 7-ADCA. Velika koncentracija supstrata poboljšala je konverziju 7-ADCA sa 61 na 81 % u procesu bez uklanjanja produkta in situ (ISPR), a s 88 na 98 % u procesu sa ISPR. Cefaleksin je lako uklonjen iz kompleksa CEX/β-naftol, a dobiveni je proizvod imao čistoću od 99 % i ukupni prinos od 70 %

Facile in-situ synthesis of floating CeO2@ expanded graphite composites with efficient adsorption and visible light photocatalytic degradation of phenol

A facile solution to obtain efficient, stable and cheap photocatalysts was conducted in this work. CeO2@ expanded graphite (CeO2/EG) composites were in-situ synthesized with a new strategy, in which CeCl3 molecules inserted the graphite intercalation compound (GIC) and converted into CeO2 as GIC changed into EG via instant calcination. The introduction of EG has accelerated the adsorption of contaminant molecules, promoted the charge transfer and improved the photocatalytic efficiency. The best sample, containing 80.75 wt% CeO2 particles of nanometer scale, has achieved the highest pollutant removal efficiency of 97.3% for phenol, displaying the highest reaction rate constant of 0.0262 min(-1), which was 35.4 times higher than CeO2. Besides, it possesses good stability and keeps floating in water pollution treatment, showing great advantages to work in natural water body. Phenol and its degradation intermediates were identified using HPLC/MS, and appropriate reaction pathways were proposed

Deep Stereo Image Compression via Bi-directional Coding

Existing learning-based stereo compression methods usually adopt a unidirectional approach to encoding one image independently and the other image conditioned upon the first. This paper proposes a novel bidirectional coding-based end-to-end stereo image compression network (BCSIC-Net). BCSIC-Net consists of a novel bidirectional contextual transform module which performs nonlinear transform conditioned upon the inter-view context in a latent space to reduce inter-view redundancy, and a bidirectional conditional entropy model that employs interview correspondence as a conditional prior to improve coding efficiency. Experimental results on the InStereo2K and KITTI datasets demonstrate that the proposed BCSIC-Net can effectively reduce the inter-view redundancy and out-performs state-of-the-art methods