Guilherme Dilarri

Immobilization of Saccharomyces cerevisiae Cells on Luffa cylindrica: a Study of a Novel Material for the Adsorption of Textile Dye

The textile industry is responsible for the disposal of a large volume of effluents containing synthetic dyes, which are considered to be highly toxic compounds for both human health and the environment. The aim of the present study was to test potential use of a renewable, low-cost product—Luffa cylindrica in disk and powder form—as adsorbent material for the treatment of textile effluents containing dyes. Saccharomyces cerevisiae cells were also immobilized on L. cylindrica to increase the adsorbent capacity. Batch experiments were conducted for the evaluation of the removal of the azo dye Direct Red 23. The Langmuir, Freundlich, and Temkin isotherms were used for a better interpretation of the data. The results showed that adsorption is more efficient at acidic pH and all adsorbent materials best fit the Langmuir model, indicating the formation of a monolayer. The isotherm results also demonstrated that the materials immobilized with the yeast had a greater sorption rate, but the cell-free L. cylindrica powder had a higher adsorbate/adsorbent interaction. The comparison with a spectrophotometrically defined standard revealed that the powder without and with yeast cells was able to achieve an acceptable removal rate of the dye from the solution. Moreover, the difference in adsorption between the powder without and with yeast cells was very small. Thus, the application of the cell-free L. cylindrica powder is economically more feasible. The findings demonstrate the potential use of L. cylindrica powder as an adsorbent for the treatment of effluents containing textile dyes.

Bioassays and coagulation studies using Moringa oleifera seeds for the removal of textile dyes

The aim of this work was to evaluate the removal of three different textile dyes through the coagulation action of the powder and supernatant of Moringa oleifera seeds. The pH of the solution and mass concentrations of the adsorbent were varied. Fourier transform infrared (FT-IR) spectrophotometry was used to evaluate the main interaction sites of the M. oleifera coagulants with the dyes. Bioassays were also conducted with Lactuca sativa and Eruca sativa seeds to evaluate the toxicity of the M. oleifera coagulants and dyes. Each dye interacted differently with the M. oleifera powder and supernatant; however, dye removal rates were higher than 70% even when varying the pH of the solution. FT-IR spectrophotometry revealed that the linkage of the dyes with the M. oleifera coagulants occurs through chemical interactions, and the coagulating protein of M. oleifera was confirmed as the removing agent. Depending on the dye molecule, the pH of the solution also exerted a strong influence on coagulation. The phytotoxicity tests showed that the coagulants in the seeds of M. oleifera are more toxic than the dyes tested. In conclusion, although efficient and economically feasible, the application of M. oleifera coagulants requires further investigation, especially with regard to ecotoxicology.

A simplified curcumin targets the membrane of Bacillus subtilis

Curcumin is the main constituent of turmeric, a seasoning popularized around the world with Indian cuisine. Among the benefits attributed to curcumin are anti‐inflammatory, antimicrobial, antitumoral, and chemopreventive effects. Besides, curcumin inhibits the growth of the gram‐positive bacterium Bacillus subtilis. The anti‐B. subtilis action happens by interference with the division protein FtsZ, an ancestral tubulin widespread in Bacteria. FtsZ forms protofilaments in a GTP‐dependent manner, with the concomitant recruitment of essential factors to operate cell division. By stimulating the GTPase activity of FtsZ, curcumin destabilizes its function. Recently, curcumin was shown to promote membrane permeabilization in B. subtilis. Here, we used molecular simplification to dissect the functionalities of curcumin. A simplified form, in which a monocarbonyl group substituted the β‐diketone moiety, showed antibacterial action against gram‐positive and gram‐negative bacteria of clinical interest. The simplified curcumin also disrupted the divisional septum of B. subtilis; however, subsequent biochemical analysis did not support a direct action on FtsZ. Our results suggest that the simplified curcumin exerted its function mainly through membrane permeabilization, with disruption of the membrane potential necessary for FtsZ intra‐cellular localization. Finally, we show here experimental evidence for the requirement of the β‐diketone group of curcumin for its interaction with FtsZ.

Saccharomyces cerevisiae immobilized onto cross-linked chitosan beads: application of a novel material for the removal of dye toxicity

ABSTRACT Waste from textile industries can severely harm the environment. Dyes are the main residues of these effluents. Saccharomyces cerevisiae is already known to be an efficient adsorbent for the removal of dyes. However, the lack of applicability and limitation of the use of cell biomass in an industrial treatment makes it impossible to apply them. Thus the aim of this work was to immobilize S. cerevisiae in cross-linked chitosan beads by two different techniques (contact immobilization and encapsulation in the polymer matrix), proposing two new materials for adsorption. Adsorption experiments were carried out to analyse the kinetics, isotherm and thermodynamics adsorptive of the synthesized materials. The adsorption data obtained were compared with the S. cerevisiae biomass and with the cell-free cross-linked chitosan beads to evaluate the efficiency of the two synthesized materials. The Fourier transform infrared spectrophotometer was used to characterize and analyse the main adsorption sites of the tested materials. Bioassays using the microcrustacean Daphnia similis verified if the materials could reduce the toxicity of the medium after its application in the treatment. Both materials synthesized in this work can potentially remove dyes from effluents, in addition to being able to significantly decrease dye toxicity from an aqueous medium.

An approach to textile dye removal using sawdust from Aspidosperma polyneuron

Abstract The textile industry is responsible for discarding wastewater contaminated with dyes. The timber industry generates waste in the form of sawdust. The aim of the present study was to evaluate the adsorptive potential of sawdust obtained from the Aspidosperma polyneuron tree for the removal of the textile dye from wastewater. Sawdust was subjected to different pre-treatments (acid, alkaline and polyethyleneimine) in order to increase its adsorption capacity. Based on the results from the isotherms, treatment with polyethyleneimine (PEI) led to the greatest adsorption capacity and fits the Freundlich model, indicating cooperative adsorption. Other treatments with sawdust best fit the Langmuir model, but the untreated sawdust presented better results than the treated sawdust. These results were only surpassed by sawdust treated with PEI. A. polyneuron revealed good potential for use as an adsorbent to remove dyes, which is a novel result, since to date there is no study on its use as a sorbent material.

Electrolytic treatment and biosurfactants applied to the conservation of Eugenia uniflora fruit

Microorganisms are the primary responsible for food poisoning and food spoilage. The purpose of this study was to evaluate different fruit washing methods with tap water, electrolyzed water and rhamnolipids solution produced by Pseudomonas aeruginosa LBI, in order to inhibit microbial growth. The tested organism was Eugenia uniflora. The fruits were washed and periodically inoculated into culture media to evaluate and count the colonies on the fruit surface. It was also observed the deterioration level of the fruits after each treatment. The results showed that treatment with rhamnolipids were the most efficient, inhibiting the growth of fungi and bacteria. The electrolyzed water proved to be very efficient in bacterial inhibition at the initial time, but in the final time it did not present any inhibitory effect. The electrolyzed water was also not effective in eliminating fungus. Washing with tap water was the less efficient treatment of all. The only treatment that showed an increased durability has been with rhamnolipids, increasing shelf life by up to two days. Thus rhamnolipids are the most recommended method for fruits sanitation.