Síntese enzimática de ésteres de açúcar: surfactantes e polímeros como novos materiais ambientalmente seguros

Sugar esters are substances which possess surfactant, antifungical and bactericidal actions and can be obtained through two renewable sources of raw materials: sugars and vegetable oils. Their excellent biodegradability, allied to lhe fact that they are non toxic, insipid, inodorous, biocompatible, no-ionic, digestible and because they can resist to adverse conditions of temperature, pH and salinity, explain lhe crescent use of these substances in several sections of lhe industry. The objective of this thesis was to synthesize and characterize surfactants and polymers containing sugar branched in their structures, through enzymatic transesterification of vinyl esters and sugars, using alkaline protease from Bacillus subtilis as catalyst, in organic medium (DMF).Three types of sugars were used: L-arabinose, D-glucose and sucrose and two types of vinyl esters: vinyl laurate and vinyl adipate. Aiming to reach high conversions from substrates to products for a possible future large scale industrial production, a serie of variables was optimized, through Design of Experiments (DOE), using Response Surface Methodology (RSM).The investigated variables were: (1) enzyme concentration; (2) molar reason of substrates; (3) water/solvent rale; (4) temperature and (5) time. We obtained six distinct sugar esters: 5-0-lauroyl L-arabinose, 6-0-lauroyl D-glucose, 1'-O-lauroyl sucrose, 5-0-vinyladipoyl L-arabinose, 6-0-vinyladipoyl D-glucose and 1 '-O-vinyladipoyl sucrose, being lhe last three polymerizable. The progress of lhe reaction was monitored by HPLC analysis, through lhe decrease of sugar concentration in comparison to lhe blank. Qualitative analysis by TLC confirmed lhe formation of lhe products. In lhe purification step, two methodologies were adopted: (1) chromatographic column and (2) extraction with hot acetone. The acylation position and lhe chemical structure were determined by 13C-RMN. The polymerization of lhe three vinyl sugar esters was possible, through chemical catalysis, using H2O2 and K2S2O8 as initiators, at 60°C, for 24 hours. IR spectra of lhe monomers and respective polymers were compared revealing lhe disappearance of lhe vinyl group in lhe polymer spectra. The molar weights of lhe polymers were determined by GPC and presented lhe following results: poly (5-0-vinyladipoyl L-arabinose): Mw = 7.2 X 104; PD = 2.48; poly (6-0-vinyladipoyl D-glucose): Mw = 2.7 X 103; PD = 1.75 and poly (1'-O-vinyladipoyl sucrose): Mw = 4.2 X 104; PD = 6.57. The six sugar esters were submitted to superficial tension tests for determination of the critical micelle concentrations (CMC), which varied from 122 to 167 ppm. Finally, a study of applicability of these sugar esters, as lubricants for completion fluids of petroleum wells was' accomplished through comparative analysis of lhe efficiency of these sugar esters, in relation to three commercial lubricants. The products synthesized in this thesis presented equivalent or superior action to lhe tested commercial products

Segurança Alimentar e Controle de Qualidade: um estudo da implantação do Programa Alimentos Seguros em supermercados de bairro

This study aimed to analyze the percentage of compliance, related to the requirements of Practice, achieved by 23 supermarkets in neighborhood after the deployment of Food Insurance Program. For its development research methodology adopted was the application start and end of a check-list (tool-specific SBP) in 23 supermarkets, target of this study. After the deployment of PAS was made a comparative study where it was possible to see that these companies need to improve conditions related to food safety, because according to the study, none of the 23 supermarkets evaluated met the criteria recommended by the SBP to 100% of compliance for the items critical of the check-list. Only 04 of the 23 supermarkets were in the range of 80 to 90% of the overall percentage of compliance, representing only 17.3% of the sample. Most of the sample submitted in a regular situation, according to the methodology of Cardoso (2001). Of the 23 supermarkets studied, 03 supermarkets were classified as poor (13.04%), 13 as scheduled (56.52%) as good and 07 (30.43%). You can see improvements in a small part of the sample, but the decline in the percentage of compliance of 02 companies after working for the implementation of the program, showing lack of responsibility and commitment of companies which should have as its top priority to food safety that market

Seguros de desempleo, objetivos, características y situación en América Latina

Incluye Bibliografía

Incertidumbre económica, seguros sociales, solidaridad y responsabilidad fiscal

Incluye Bibliografía

Un matrimonio difícil: la convivencia entre un seguro público solidario y seguros de salud competitivos

Incluye Bibliografía

Seguros de desempleo y reformas recientes en América Latina

Incluye Bibliografía

Impuestos diferenciales a las gasolinas y sus efectos en la demanda de automóviles

Incluye Bibliografía

El mercado de seguros de salud: lecciones sobre el conflicto entre equivalencia y solidaridad

Incluye Bibliografía

Sistema de responsabilidad y seguros en el caso de contratos de transporte multimodal internacional

Incluye Bibliografía