Optimization of the enzymatic production of isoamyl acetate with novozym 435 from candida antarctica

In this study the production of isoamyl acetate by esterification of isoamyl alcohol and acetic acid was carried out using immobilized C . antarctica lipase (Novozym 435) as a catalyst without any organic solvent. The esterification yield was optimized with response surface methodology. This method was used with four parameters to evaluate the effects of important variables on the esterification yield. The parameters are acid/alcohol mole ratio (0.2-0.8), enzyme amount (4-12%, w/w), temperature (30-50 °C), and reaction time (4-8 hr). It was found that the most effective parameter was acid/alcohol mole ratio. As acid/alcohol mole ratio increased at any given reaction time and amount of enzyme, ester concentration, C p (mmol ester/g mixture), increased up to an acid/alcohol mole ratio of 0.7 and thereafter decreased. The model indicated the optimum conditions for maximum esterification (3.45 mmol ester/g mixture) in the acid/alcohol mole ratio of 0.52 for 8.15% enzyme at 43.2 °C and after 5.27 hr, which were in good agreement with the experimental value (3.5 mmol ester/g mixture).     

Synthesis of submicron AlN powder using dynamic/thermochemical method

Carbothermal reduction and nitridation (CRN) method, used for the synthesis of nitride-based ceramic powders, is an effective and economic technique that has been widely investigated. In this study, a CRN-based novel approach, denominated as dynamic/thermochemical method (DTM), has been used to synthesize submicron high-purity aluminum nitride (AlN) powders with equiaxed-sized particles. DTM is a modified CRN method in which the reaction takes place in a controlled atmosphere using a rotary tube furnace, allowing the synthesis of fine particle-size powders in a relatively short time. Following the DTM process, homogeneous submicron AlN powders were synthesized from a mixture of aluminum hydroxide (Al(OH)₃) and carbon black at 1450°C for 1.5 h. Furthermore, dynamic synthesis parameters, as well as the use of ammonia (NH₃) and propane (C₃H₈) gas mixtures instead of carbon black and nitrogen, were investigated.     

Seedless growth of zinc oxide flower-shaped structures on multilayer graphene by electrochemical deposition

A seedless growth of zinc oxide (ZnO) structures on multilayer (ML) graphene by electrochemical deposition without any pre-deposited ZnO seed layer or metal catalyst was studied. A high density of a mixture of vertically aligned/non-aligned ZnO rods and flower-shaped structures was obtained. ML graphene seems to generate the formation of flower-shaped structures due to the stacking boundaries. The nucleation of ZnO seems to be promoted at the stacking edges of ML graphene with the increase of applied current density, resulting in the formation of flower-shaped structures. The diameters of the rods/flower-shaped structures also increase with the applied current density. ZnO rods/flower-shaped structures with high aspect ratio over 5.0 and good crystallinity were obtained at the applied current densities of −0.5 and −1.0 mA/cm². The growth mechanism was proposed. The growth involves the formation of ZnO nucleation below 80°C and the enhancement of the growth of vertically non-aligned rods and flower-shaped structures at 80°C. Such ZnO/graphene hybrid structure provides several potential applications in sensing devices.     

Determination of hydroquinone using poly(3‐methylthiophene) synthesized electrochemically on pt electrode in methylene chloride

Poly(3‐methylthiophene) (P3MT) film was synthesized by potentiodynamic method on Pt electrode in methylene chloride solution containing 0.10M tetrabuthlammonium perchlorate supporting electrolyte and used for the determination of hydroquinone (HQ) with amperometric I–t method in solution consisting of NaHSO₄/Na₂SO₄ (SBS; pH 2.0). This modified electrode has a lower working potential and good operational stability due to reducing electrode fouling when compared with the direct oxidation of HQ at the bare Pt electrode. Limit of detection, limit of quantification, and the linear response range were found to be 1.32 × 10^?5 mM, 4.41 × 10^?5 mM, and between 4.41 × 10^?5 – 50.0 mM (R² = 0.997), at 0.50 V versus saturated calomel electrode, respectively. HQ determination in complex matrix was checked using real samples to demonstrate the applicability of modified electrode. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40859.     

Catalyst incorporation at defects during nanowire growth

Scanning and transmission electron microscopy was used to correlate the structure of planar defects with the prevalence of Au catalyst atom incorporation in Si nanowires. Site-specific high-resolution imaging along orthogonal zone axes, enabled by advances in focused ion beam cross sectioning, reveals substantial incorporation of catalyst atoms at grain boundaries in <110> oriented nanowires. In contrast, (111) stacking faults that generate new polytypes in <112> oriented nanowires do not show preferential catalyst incorporation. Tomographic reconstruction of the catalyst-nanowire interface is used to suggest criteria for the stability of planar defects that trap impurity atoms in catalyst-mediated nanowires.     

Identification of a novel structure in heparin generated by sequential oxidative-reductive treatment

Unfractionated heparin is isolated from animal organs, predominantly porcine intestinal mucosa, and goes through an extensive process of purification before it can be used for pharmaceutical purposes. While the structural microheterogeneity of heparin is predominantly biosynthetically imprinted in the Golgi, subsequent steps involved in the purification and manufacture of commercial heparin can lead to the introduction of additional modifications. Postheparin crisis of 2008, it has become increasingly important to identify what additional structural diversity is introduced as a function of the purification process and thus can be determined as being heparin-related, as opposed to being an adulterant or contaminant, e.g., oversulfated chondroitin sulfate. Our study focuses on the identification of a previously unreported structure in heparin that arises due to specific steps used in the manufacturing process. This structure was initially observed as a disaccharide peak in a complete enzymatic digest of heparin, but its presence was later identified in the NMR spectra of intact heparin as well. Structural elucidation experiments involved isolation of this structure and analysis based on multidimensional NMR and liquid chromatography coupled with mass spectrometry (LC-MS). Heparin was also subjected to specific chemical reactions to determine which steps in the manufacturing process are responsible for this novel structure. Our results allowed for the definitive assignment of the structure of this novel process-related modification and enabled an identification of the putative steps in the process that give rise to the structure.     

Biodegradation kinetics of the soluble slowly biodegradable substrate in polyamide carpet finishing wastewater

BACKGROUND: Carpet manufacturing and finishing with purely synthetic fibers has received relatively little attention, compared to other textile processing types. This study evaluates the biodegradation kinetics of organic compounds generated from polyamide‐based carpet manufacturing. RESULTS: Experiments were conducted on pre‐washing and dyeing/softening wastewater effluents. Model evaluation of oxygen uptake rate profiles with dual hydrolysis kinetics revealed that the soluble slowly hydrolysable chemical oxygen demand (COD) was the major fraction, constituting nearly 97% of the biodegradable COD and 78% of total COD content. Degradation of the slowly hydrolysable COD fraction was characterized with a rate coefficient of 0.72 day^?1, a significant rate limiting step for substrate utilization. Model simulation of system performance indicated that an unusually long hydraulic retention time was required for an activated sludge system to reduce the effluent COD concentration. CONCLUSION: Compared to domestic wastewater, two additional hydrolysable COD fractions with different degradation kinetics were characterized. The dyeing and softening step had the highest slowly biodegradable organic matter content, with the lowest degradation rate. Simulation results showed that soluble slowly hydrolysable COD degradation did not cause any problem in terms of effluent quality. With the system operated under reduced solids retention time, the effluent COD quality was significantly influenced by the slow hydrolysis rate of soluble hydrolysable matter. Copyright © 2007 Society of Chemical Industry