Synthesis of novel antibacterial and antifungal dithiocarbamate-containing piperazine derivatives via re-engineering multicomponent approach.

A metal-free multicomponent synthetic route for the diverse preparation of dithiocarbamate-containing piperazine derivatives was developed through the C-N bond cleavage of DABCO ring. This multicomponent re-engineering approach proceeds via the reaction of amines, CS2 and DABCO salts in one pot. Various DABCO salts and secondary amines are tolerated well in this protocol to afford a broad spectrum of dithiocarbamate-containing piperazines in good to high yields. Then, the selected compounds have been deployed against some critical types of bacteria and fungi. A certain number of synthesized compounds revealed not only appropriate antibacterial activity as investigated by disc fusion and minimum inhibitory concentration methods against bacteria (Gram-positive and Gram-negative), but also depicted good to excellent antifungal activity.

Synthesis of a new chitosan-p-tert-butylcalix[4]arene polymer as adsorbent for toxic mercury ion.

In this paper, we have synthesized a novel chitosan-p-tert-butylcalix[4]arene polymer (CCP) as a highly efficient adsorbent for mercury ion (Hg2+) removal from water. In fact, a lower rim diamine derivative of p-tert-butylcalix[4]arene has been cross-linked with chitosan chain by carbonyl diimidazole (CDI) as the linker. CDI forms a urea linkage between calix[4]arene diamine derivative and amine groups of the chitosan polymeric chain. The structure and properties of the new polymer were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscope. Also, the adsorption capacity of CCP was studied towards Hg2+ in aqueous medium by inductively coupled plasma-optical emission spectrometry. Interestingly, the results showed a considerable adsorption capacity for CCP in comparison with chitosan. Therefore, CCP can be introduced as a promising adsorbent for the elimination of Hg2+ from wastewaters. Moreover, because of the conformity of adsorption kinetic with pseudo-second-order kinetic models, it can be concluded that chemical adsorption has an important role between functional groups on CCP polymer and Hg2+ ions. In addition, according to Freundlich isotherm, the CCP surface was heterogeneous with different functional groups.

Slime molds as a valuable source of antimicrobial agents.

Given the emerging multidrug-resistant pathogens, the number of effective antimicrobial agents to deal with the threat of bacterial and fungal resistance has fallen dramatically. Therefore, the critical solution to deal with the missing effective antibiotics is to research new sources or new synthetic antibiotics. Natural products have different advantages to be considered antimicrobial agents. There are different natural sources for antimicrobial agents, such as bacteria, fungi, algae, slime molds, and plants. This article has focused on antibiotics from slime molds, especially Myxomycetes. The reason why slime molds have been chosen to be studied is their unique bioactive metabolites, especially over the past couple of decades. Some of those metabolites have been demonstrated to possess antibiotic activities. Hence, this article has focused on the potential of these creatures as an alternative source of antibiotics.

Augmenting the expression of accD and rbcL genes using optimized iron concentration to achieve higher biomass and biodiesel in Chlorella vulgaris.

Chlorella vulgaris is a form of microalgae commonly employed as a biological source of oil for biodiesel production. Major algal cultivation strategies are focused on stimulating growth rate and lipid content. In the present study, the algal growth media was supplemented with iron (III) chloride (FeCl3), as a stimulating factor for growth and lipid production, in three iron concentrations including 90, 200, and 500 µM. The turbidity of algal cells was measured on different days, to determine the growth rate. In optimum iron concentration, this measurement experienced a 2.1-fold increase. Next, the lipid content was extracted, and the amount of lipid produced in each treatment was calculated, which demonstrated a 4.57-fold increase in lipid productivity. The expression of genes corresponding to the metabolic enzymes (i.e. acetyl-CoA carboxylase (accD) and ribulose bisphosphate carboxylase large chain (rbcL)) was evaluated using real-time PCR under different initial iron feeds. As demonstrated in the results, the initial iron feed of 90 µM was an optimum concentration that obtained the highest growth rate, more cell density, and increased lipid production. In 90 µM initial iron concentration, the expression of accD and rbcL genes showed a 4.8- and 35-fold increase, respectively, compared to that of the control genes. Based on the results, this optimum iron concentration could satisfy the industrial interest in biodiesel production from C. vulgaris as a potential stimulating factor. However, higher levels of iron (e.g. 200 and 500 µM) failed to act as positive stress for increasing biodiesel production. Finally, in this paper, different mechanisms where iron affects acetyl-CoA carboxylase (ACCase) and 1,5-ribulose bisphosphate carboxylase/oxygenase (RuBisCo) are illustrated.

Utilizing dextran to improve hemocompatibility of antimicrobial wound dressings with embedded quaternary ammonium salts.

Dextran, a polysaccharide with interfering effects on coagulation hemeostasis was utilized to compensate the hostile effects of quaternary ammonium salts (QAS) embed in the backbone of a wound dressing membrane as an antimicrobial agent. Despite the high antimicrobial efficiency of QAS, their adverse hemolytic effect on red blood cells is a challenging problem for using them as an active antiseptic agent in wound dressings. To this end, wound dressings made through the sol-gel hydrolysis and polycondensation reaction of a methoxysilane-functionalized quaternary ammonium compound (Si-RQ) and a methoxysilane terminated polyurethane prepolymer (Si-PPU), at different compositions, were surface modified with dextran. The final dressings were then subjected to various biological and physico-mechanical assays. The low hemolysis rate and prolonged clot formation on dextran-modified dressings confirmed their excellent hemocompatibility. Meanwhile, the optimized dressings preserved their excellent antimicrobial activity against both Gram-positive and Gram-negative bacteria and a fungal strain up to 100% killing efficiency. In addition, they exhibited very good cytocompatibility since the fibroblast cells could grow and proliferate efficiently on their surface. The recorded results confirmed the effectiveness of surface anchored dextran for regulation of hemocompatibility of QAS containing wound dressings without deterioration of their basic physical and biological properties.

Equilibrium Isotherm, Kinetic Modeling, Optimization, and Characterization Studies of Cadmium Adsorption by Surface-Engineered Escherichia coli

Background: Amongst the methods that remove heavy metals from environment, biosorption approaches have received increased attention because of their environmentally friendly and cost-effective feature, as well as their superior performances. Methods: In the present study, we investigated the ability of a surface-engineered Escherichia coli, carrying the cyanobacterial metallothionein on the cell surface, in the removal of Ca (II) from solution under different experimental conditions. The biosorption process was optimized using central composite design. In parallel, the kinetics of metal biosorption was studied, and the rate constants of different kinetic models were calculated. Results: Cadmium biosorption is followed by the second-order kinetics. Freundlich and Langmuir equations were used to analyze sorption data; characteristic parameters were determined for each adsorption isotherm. The biosorption process was optimized using the central composite design. The optimal cadmium sorption capacity (284.69 nmol/mg biomass) was obtained at 40°C (pH 8) and a biomass dosage of 10 mg. The influence of two elutants, EDTA and CaCl2, was also assessed on metal recovery. Approximately, 68.58% and 56.54% of the adsorbed cadmium were removed by EDTA and CaCl2 during desorption, respectively. The Fourier transform infrared spectrophotometer (FTIR) analysis indicated that carboxyl, amino, phosphoryl, thiol, and hydroxyl are the main chemical groups involved in the cadmium bioadsorption process. Conclusion: Results from this study implied that chemical adsorption on the heterogeneous surface of E. coli E and optimization of adsorption parameters provides a highly efficient bioadsorbent.

Surface display of bacterial metallothioneins and a chitin binding domain on Escherichia coli increase cadmium adsorption and cell immobilization.

To increase the level of adsorption of cadmium ions to the surface of Escherichia coli, we fused cyanobacterial metallothioneins, SmtA (from Synechococcus elongatus PCC 3601) and MtnA (from Synechococcus vulcanus) to the E. coli cell surface using a Lpp'-OmpA-based display system. E. coli strains expressing Lpp'-OmpA-SmtA-linker-ChBD (chitin-binding domain from Bacillus pumillus SG2 chitinase S; chiS) and Lpp'-OmpA-MtnA-linker-ChBD on their surface adsorbed more cadmium compared to the E. coli cells expressing only the Lpp'-OmpA-linker-ChBD hybrid. These constructs also were bound to chitin through their chitin-binding domain, allowing them to be immobilized on a chitin matrix. We assessed surface presentation of Lpp'-OmpA-SmtA-linker-ChBD, Lpp'-OmpA-MtnA-linker-ChBD, and Lpp'-OmpA-linker-ChBD using immunostaining. The Lpp'-OmpA-SmtA-linker-ChBD chimera adsorbed metal and was bound to chitin with the highest efficiency compared to the other chimeras, suggesting that it is an effective bioadsorbent. This is the first example of coupling metal adsorption with cell immobilization using a whole-cell bioadsorbent.