Degradation of cationic surfactants using immobilized bacteria: Its effect on adsorption to activated sludge.

Adsorption of cationic surfactants (QACs) Br-tetradecyltrimethylammonium (TTAB), Cl-tetradecylbenzyldimethylammonium (C14BDMA) and Cl-hexadecylbenzyldimethylammonium (C16BDMA) to activated sludge from a wastewater treatment plant was tested. Adsorption equilibrium was reached after 2 h, and for initial 200 mg L-1 81%, 90% and 98% of TTAB, C14BDMA and C16BDMA were respectively adsorbed. After six successive desorption cycles, 21% of TTAB and 12.7% of C14BDMA were desorbed from the sludge. In agreement with the percentage of QACs pre-adsorbed, the more hydrophobic the compound, the lesser the extent of desorption. Wastewater samples with activated sludge were supplemented with TTAB 200 mg L-1 and Ca-alginate beads containing the QACs-degrading microorganisms Pseudomonas putida A (ATCC 12633) and Aeromonas hydrophila MFB03. After 24 h, 10 mg L-1 of TTAB were detected in the liquid phase and 6-8 mg L-1 adsorbed to the sludge. Since without Ca-alginate beads or with empty beads total TTAB amount (phase solid and liquid) did not change, the 90% reduction of the initial 200 mg L-1 after treatment with immobilized cells was attributed to the bacterial consortium's capacity to biodegrade QACs. The results show the advantages of using immobilized bacteria to achieve complete QACs elimination from wastewater systems, thus preventing them from reaching the environment.

Los significados sobre la alimentación saludable de mujeres de un barrio periférico de la ciudad de Córdoba (Argentina) / The Beliefs Surrounding Healthy Eating Habits of Women in an out-Lying Neighborhood of the City of Córdoba (Argentina)

Resumen Antecedentes: la comida constituye un consumo material y simbólico, diferencial y diferenciador, cuyos sentidos sobre lo sano entran en tensión con las posibilidades de acceso material, las circunstancias y los valores socioculturales. Objetivo: reconstruir los significados sobre la alimentación saludable de mujeres del barrio Ampliación Ferreyra (Córdoba Capital). Materiales y métodos: metodología cualitativa. La muestra intencional y teórica estuvo conformada por siete mujeres adultas, residentes en el barrio, entrevistadas en profundidad. Para el análisis se realizó la codificación de segmentos significativos, el ordenamiento, análisis descriptivo, reducción e interpretación del material. Resultados: se trama conflictivamente el par significante alimentación/comida, que remite a sentidos contradictorios entre el discurso de la salud pública y las sensaciones y emociones, respectivamente. Se recuperaron expresiones que comportan posturas morales y sentimientos de pertenencia o repudio al barrio mediante los relatos sobre la comida, así como narraciones que rememoran el sentido colectivo de la comida cuando su materialidad se encuentra amenazada. Conclusiones: los enunciados (re)producidos desde el campo de la nutrición como formas de pensar, escribir, hablar y hacer sobre la comida intervienen en la construcción de subjetividades; esto obliga a repensar las consecuencias "no previstas" respecto del rol de la Salud Pública y la Educación Alimentaria Nutricional.

Abstract Background: Food is both a material and symbolic entity, both distinguishing and differentiating, and of which the various beliefs surrounding "health" contribute to the tensions of material possessions, current circumstances, and socio-cultural values. Objective: To reconstruct women's understanding and beliefs of healthy food in the Ampliación Ferreyra neighborhood of Cordoba, Argentina. Materials and Methods: Qualitative methodology. The sample consisted of seven adult women residing in the neighborhood and who participated in in-depth interviews. Data was analyzed through coding and was then ordered into significant groupings. Descriptive analyses and interpretation of the material was then conducted. Results: A contradiction was found between how food words are described by public health and how the sample women emotionally identify with those words. The women identify with these words and foods more as how they relate to behaviors, feelings of belonging or not within the neighborhood, and cooking and eating meals. The foods become part of the collective stories and emotions of the neighborhood, as well as potentially evoking feelings of food insecurity. Conclusions: Statements produced by the field of nutrition as ways of thinking, writing, speaking, and preparations related to food intervene in the construction of more subjective ideas. This calls for a re-thinking of unforeseen consequences in respect to the roll of Public Health and Nutrition Education.

Release of outer membrane vesicles in Pseudomonas putida as a response to stress caused by cationic surfactants.

Pseudomonas putida A (ATCC 12633), a degrader of cationic surfactants, releases outer membrane vesicles (OMVs) when grown with tetradecyltrimethylammonium bromide (TTAB) as the sole carbon, nitrogen and energy source. The OMVs exhibit a bilayer structure and were found to be composed of lipopolysaccharides, proteins and phospholipids (PLs) such as cardiolipin, phosphatidylcholine, phosphatidic acid and phosphatidylglycerol (PG). The OMVs showed a marked increase in the PG content, approximately 43 % higher than the amount registered in the parent cells from which the vesicles were derived. After growth of P. putida with TTAB, the amount of lipoprotein covalently cross-linked to the peptidoglycan showed a twofold decrease when compared with values found after growth without the surfactant [16 ± 2 and 28 ± 3 µg (mg cell envelope protein)- 1, respectively]. This decrease in the amount of lipoprotein can be related to areas of loss of contact between the outer membrane and the peptidoglycan and, therefore, to OMV production. In addition, due to its amphiphilic nature, TTAB can contribute to OMV biogenesis, through a physical mechanism, by induction of the curvature of the membrane. Taking into account that OVMs were produced when the cells were grown under external stress, caused by the surfactant, and that TTAB was detected in the vesicles [48 nmol TTAB (nmol PL)- 1], we concluded that this system of TTAB elimination is a mechanism that P. putida A (ATCC 12633) would utilize for alleviating stress caused by cationic surfactants.

Degradation of cationic surfactants using Pseudomonas putida A ATCC 12633 immobilized in calcium alginate beads.

In this study, the degradation of tetradecyltrimethylammonium bromide (TTAB) by freely suspended and alginate-entrapped cells from the bacteria Pseudomonas putida (P. putida) A ATCC 12633 was investigated in batch cultures. The optimal conditions to prepare beads for achieving a higher TTAB degradation rate were investigated by changing the concentration of sodium alginate, pH, temperature, agitation rate and initial concentration of TTAB. The results show that the optimal embedding conditions of calcium alginate beads are 4 % w/v of sodium alginate content and 2 × 10(8) cfu ml(-1) of P. putida A ATCC 12633 cells that had been previously grown in rich medium. The optimal degradation process was carried out in pH 7.4 buffered medium at 30 °C on a rotary shaker at 100 rpm. After 48 h of incubation, the free cells degraded 26 mg l(-1) of TTAB from an initial concentration of 50 mg l(-1) TTAB. When the initial TTAB concentration was increased to 100 mg l(-1), the free cells lost their degrading activity and were no longer viable. In contrast, when the cells were immobilized on alginate, they degraded 75 % of the TTAB after 24 h of incubation from an initial concentration of 330 mg l(-1) of TTAB. The immobilized cells can be stored at 4 °C for 25 days without loss of viability and can be reused without losing degrading capacity for three cycles.