Assessment of Physical Process Conditions for Enhanced Production of Novel Glutaminase-Free L-Asparaginase from <Emphasis Type="BoldItalic">Pectobacterium carotovorum</Emphasis> MTCC 1428

Statistically based experimental design was applied to maximize the production of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428. The effect of physical process parameters (initial pH of the medium, temperature, rpm of the shaking incubator, and inoculum size) on the production of L-asparaginase from P. carotovorum MTCC 1428 was studied using central composite design technique. The individual optimum levels of initial pH of the medium, temperature, rpm of shaking incubator, and inoculum size were found to be 6.90, 29.8 °C, 157 rpm, and 2.61% (v/v), respectively, for the production of L-asparaginase. After physical process parameters optimization, the production and productivity of L-asparaginase was enhanced by 26.39% (specific activity) and 10.19%, respectively. Maximization of L-asparaginase production was achieved at 12 h under optimal levels of physical process parameters in shake flask level.     

Bioprocess Optimization of Furanocoumarin Elicitation by Medium Renewal and Re-elicitation: A Perfusion-Based Approach

Effect of various abiotic (methyl jasmonate, salicylic acid) and biotic (yeast extract, Aspergillus niger) elicitors on furanocoumarin production and in situ product removal was studied using shoot cultures of Ruta graveolens L. Elicitation by yeast extract (1% w/v) on day 15 was most effective. It led to 7.8-fold higher furanocoumarin production that was attained 24 h after elicitation and 43% of the product was released into the medium. Changes in the relative concentration of furanocoumarins produced depend on the elicitor used. Molar ratio of bergapten increased to 93% in response to yeast extract. With the perspective of developing a commercially feasible process, an approach for preserving viability of biomass and its reuse needs to be developed. For this, medium renewal strategy was investigated. Removal of the spent medium 48 h after elicitation allowed in situ product removal and proved effective in revival of cultures, allowing reuse of biomass. A week after medium renewal, the revived biomass was re-elicited and a second furanocoumarin production peak was obtained. A perfusion-based bioprocess optimization approach, employing elicitation coupled with medium renewal with subsequent re-elicitation, as a new strategy for improved furanocoumarin production, has been suggested.     

Cellulase-Producing Bacteria from Thai Higher Termites, <Emphasis Type="Italic">Microcerotermes</Emphasis> sp.: Enzymatic Activities and Ionic Liquid Tolerance

The three highest hydrolysis-capacity-value isolates of Bacillus subtilis (A 002, M 015, and F 018) obtained from Thai higher termites, Microcerotermes sp., under different isolation conditions (aerobic, anaerobic, and anaerobic/aerobic) were tested for cellulase activities—FPase, endoglucanase, and β-glucosidase—at 37 °C and pH 7.2 for 24 h. Their tolerance to an ionic liquid, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), was also investigated. The results showed that the isolate M 015 provided the highest endoglucanase activity whereas the highest FPase and β-glucosidase activities were observed for the isolate F 018. The isolate F 018 also showed the highest tolerance to [BMIM]Cl in the range of 0.1–1.0 vol.%. In contrast, the isolate A 002 exhibited growth retardation in the presence of 0.5–1.0 vol.% [BMIM]Cl.     

Effects of amorphous poly(vinyl acetate) on crystalline morphology of poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid)

The amorphous and crystalline phase behavior, spherulite morphology, and interactions between amorphous poly(vinyl acetate) (PVAc) and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) were examined using differential scanning calorimetry, polarized-light optical and scanning electron, atomic-force microscopy (DSC, POM, SEM, AFM), and small-angle X-ray scattering (SAXS). The PHBV/PVAc blend was found to be miscible with an almost linear T _g-composition relationship, indicating perfect homogeneity. Interaction parameter by melting point depression is a negative value of χ = −0.32, suggesting quite favorable interaction strength. With the intimate interaction between the amorphous PVAc and crystalline PHBV polymers, effects of PVAc on the spherulitic morphology of PHBV are quite significant. Owing to the higher T _g of PVAc (than that of PHBV), the spherulite growth rate of PHBV was depressed by increasing PVAc content in blends. Neat PHBV exhibits ring-banded spherulites when crystallized at T_c = 60 ~ 110^° C {T_{\rm{c}}} = {6}0\sim {11}0^\circ {\hbox{C}} ; however, with increasing PVAc content in the blends, the temperature range at which the PHBV/PVAc blends exhibit ring-banded spherulites remains similar but the regularity increases, and the inter-ring spacing significantly decreases. In addition, the spherulite size and ring-band patterns therein are strongly dependent on T _max (190 vs. 220 °C, respectively, for erasing prior nuclei), from which the blends were quenched to a T _c (60–110 °C) for crystallization. For PHBV/PVAc blends crystallized at the same T _c from different T _max, higher T _max tends to erase nuclei, leading to larger spherulites. However, such larger spherulites owing to higher T _max are not necessarily packed with thicker lamellae.     

Chemical synthesis and optical properties of CdS–poly(lactic acid) nanocomposites and their transparent fluorescent films

This paper describes the first synthesis of cadmium sulfide (CdS)-poly(lactic acid) (PLA) nanocomposites and their transparent fluorescent films by covalently grafting PLA onto the surfaces of CdS nanocrystals (NCs). Synthesis of the nanocomposites involved two steps. Lactic acid (LA)-capped CdS NCs were first prepared by reacting cadmium chloride (CdCl₂) with sodium sulfide (Na₂S) using LA as the organic ligand in H₂O/N,N-dimethylformamide (DMF) solution. CdS–PLA nanocomposites were then formed by in situ ring-opening polymerization of lactide on the surface of modified CdS NCs. We also demonstrated herein the fabrication of the transparent fluorescent films of CdS–PLA nanocomposites by blending as-prepared nanocomposites with high-molecular-weight PLA. The as-prepared CdS NCs and their nanocomposites were studied by transmission electron microscopic imaging, thermogravimetric analyses, and spectroscopic measurements (ultraviolet–visible absorption and photoluminescence). The results revealed that the CdS–polymer nanocomposites exhibited good optical properties in terms of their photoluminescence and transparency.     

Special wetting behavior of a graphitic nanofiber-modified epoxy generalized for rough textured fabric surfaces

Wetting behavior of a polymer resin used as matrix on fabric surfaces is one of the key attributes for making high quality structural composites. Though incorporation of various functionalized nanoparticles can stimulate improvements to many properties of epoxy resins, there has not been any report on wettability of any nano-modified epoxy on rough inclined fabric surfaces. In this research work, wetting behavior of a previously developed nano-epoxy resin modified by a type of reactive graphitic nanofibers (r-GNFs) was investigated. The observation results revealed that a unique wetting behavior was discovered from the nano-epoxy on rough fabric surfaces due to the contribution of the r-GNFs. Based on this dramatically improved wettability of the epoxy, a concept of dry–wet contact model was proposed to interpret the different wetting phenomenon observed from the nano-epoxy and that of the pure epoxy. The improved wetting characteristics of the nano-epoxy system will be essential for enabling future energy efficient infusion processing for manufacturing high quality and high-performance structural composite applications.     

Phosphodiester hydrolysis promoted by dinuclear iron(III) complexes

We report the reactivity of three binuclear non-heme Fe(III) compounds, namely [Fe₂(bbppnol)(μ-AcO)(H₂O)₂](ClO₄)₂ (1), [Fe₂(bbppnol)(μ-AcO)₂](PF₆) (2), and [Fe₂(bbppnol)(μ-OH)(Cl)₂]·6H₂O (3), where H₃bbppnol = N,N′-bis(2-hydroxybenzyl)-N,N′-bis(2-methylpyridyl)–1,3-propanediamine-2-ol, toward the hydrolysis of bis-(2,4-dinitrophenyl)phosphate as models for phosphoesterase activity. The synthesis and characterization of the new complexes 1 and 3 was also described. The reactivity differences observed for these complexes show that the accessibility of the substrate to the reaction site is one of the key steps that determinate the hydrolysis efficiency.     

Synthesis,structure, and DNA-binding properties of manganese(II) and zinc(II) complexes with tris(<Emphasis Type="Italic">N</Emphasis>-methylbenzimidazol-2-ylmethyl)amine ligand

Tris(N-methylbenzimidazol-2-ylmethyl)amine (Mentb) and its two complexes, [Mn(Mentb)(DMF)(H₂O)](pic)₂ 1 and [Zn(Mentb)(pic)](pic) 2 (pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single crystal X-ray diffraction revealed that the two complexes have different structures. In complex 1, the coordination sphere around Mn(II) is distorted octahedral, whereas in complex 2 the coordination sphere around Zn(II) is distorted trigonal bipyramidal. The DNA-binding properties of the free ligand and its two complexes have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the ligand and its two complexes bind to DNA via an intercalation binding mode, and their binding affinity for DNA follows the order 1 > 2 > ligand.     

Semiquinol and phenol compounds from seven <Emphasis Type="Italic">Senecio</Emphasis> species

In this paper, examination of the aerial parts of seven Senecio species from Serbia and Montenegro is reported. Phytochemical investigation of Senecio erucifolius led to the isolation and characterization of semiquinol butyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (I), along with methyl 2-(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetate (jacaranone, II), and methyl 2-(4-hidroxyphenyl)acetate (III). The structure of I was established based on spectroscopic studies (¹H- and ¹³C-NMR, IR, and CI-MS). Compound II was also isolated from S. carpathicus and S. subalpinus. The presence of jacaranone in the methanol extracts of S. wagneri, S. othonnae, and S. paludosus was confirmed by LC/ESI-TOF MS.     

Theoretical study on transesterification in a combined process consisting of a reactive distillation column and a pervaporation unit

Steady state analysis of a combined hybrid process consisting of a reactive distillation column, pervaporation unit, and a distillation column is presented. This process configuration was first presented by Steinigeweg and Gmehling (2004) for the transesterification of methyl acetate and butanol to butyl acetate and methanol. This system is characteristic for its low reaction rate and complex phase equilibrium. Steinigeweg and Gmehling (2004) have shown that the combination of reactive distillation and pervaporation is favourable since conversions close to 100 % can be reached with a reasonable size of the reactive section in the reactive distillation column. The aim of this paper is to show that although high conversion can be achieved, very complicated steady state behaviour must be expected. The presented analysis is based on mathematical modelling of a process unit, where the steady-state analysis, including continuation and bifurcation analyses, was used. Multiple steady states were predicted for the studied system; three steady states with conversions higher than 98 %. However, not all predicted steady states met the maximal allowed temperature condition in the reactive section (catalyst maximal operation temperature of 393 K). The presence of multiple steady states reduces the operability and controllability of the reactive distillation column during its start-up and during the occurrence of any variation of operating parameters because the system can be shifted from one steady state to another one (concurrent exceeding the maximal allowed temperature) with unwanted consequences, e.g. production loss. Therefore, design and subsequent operation of such a complicated system is an ambitious task requiring knowledge of any possible system behaviour.