Maria Cristiane Rabelo

Enzymatic synthesis of prebiotic oligosaccharides.

Prebiotic oligosaccharides are nondigestible carbohydrates that can be obtained by enzymatic synthesis. Glucosyltransferases can be used to produce these carbohydrate through an acceptor reaction synthesis. When maltose is the acceptor a trisaccharide composed of one maltose unit and one glucose unit linked by an α-1,6-glycosidic bond (panose) is obtained as the primer product of the dextransucrase acceptor reaction. In this work, panose enzymatic synthesis was evaluated by a central composite experimental design in which maltose and sucrose concentration were varied in a wide range of maltose/sucrose ratios in a batch reactor system. A partially purified enzyme was used in order to reduce the process costs, because enzyme purification is one of the most expensive steps in enzymatic synthesis. Even using high maltose/sucrose ratios, dextran and higher-oligosaccharide formation were not avoided. The results showed that intermediate concentrations of sucrose and high maltose concentration resulted in high panose productivity with low dextran and higher-oligosaccharide productivity.

Enzyme synthesis of oligosaccharides using cashew apple juice as substrate.

The use of agriculture substrates in industrial biotechnological processes has been increasing because of their low cost. In this work, the use of clarified cashew apple juice was investigated as substrate for enzyme synthesis of prebiotic oligosaccharide. The results showed that cashew apple juice is a good source of reducing sugars and can be used as substrate for the production of dextransucrase by Leuconostoc citreum B-742 for the synthesis of oligosaccharides using the crude enzyme. Optimal oligosaccharide yield (approximately 80%) was obtained for sucrose concentrations lower than 60 g/L and reducing sugar concentrations higher than 100 g/L.

Produção de ácido lático e dextrana utilizando suco de caju como substrato

The main aim of the present work was to study the use of agriculture excess as substrates for dextran and lactic acid production. The fermentations were carried out with the microorganism Leuconostoc mesenteroides B512F in a medium containing cashew apple juice and sucrose. The concentrations of reducing sugar and sucrose were varied according to factorial planning. At the end of the fermentation the dextran, the lactic acid and biomass produced were quantified.The results were analyzed by the surface response analysis methodology. According to the results increasing the sugar level favors dextran and lactic acid production. The use of cashew apple juice as an alternative substrate for dextran and lactic acid production presented technical viability.

Chromatographic Separation of Isomaltooligosaccharides on Ion-Exchange Resins: Effect of the Cationic Form

Prebiotic isomaltooligosaccharides (IMOs) are composed of α-d-glucose units linked by glucosidic α (1Ø6) bonds and they remain intact until reaching the large bowels, where they are metabolized by bifidobacteria and lactobacillus. These saccharides can also be synthesized enzymatically, wherein the reaction media is composed of monosaccharides (glucose and fructose), disaccharides (sucrose and maltose), IMOs (the product of interest) and dextrans. Dextrans are readily separated by solvent precipitation; however, continuous chromatographic separation (simulated moving bed or SMB) should be an interesting option for the enrichment and purification of IMOs from mono- and disaccharides. The objective of the present work was to measure fundamental adsorption data of IMOs, mono- and disaccharides in preparative columns packed with ion-exchange resin of different cationic forms (K+, Ca+, H+ and Na+), so as to verify the influence of the cation on the selectivity and capacity. Ion exchange in H+ form showed the best performance in terms of selectivity between maltose and maltotriose, but the resin in the K+ form had superior adsorption capacities. Additionally, on the basis of equilibrium theory, optimal SMB operating conditions for resin H+ will yield the highest productivity as compared with the other cationic forms.

Evaluation of thermal and non-thermal processing effect on non-prebiotic and prebiotic acerola juices using 1 H q NMR and GC-MS coupled to chemometrics

The effects of thermal (pasteurization and sterilization) and non-thermal (ultrasound and plasma) processing on the composition of prebiotic and non-prebiotic acerola juices were evaluated using NMR and GC-MS coupled to chemometrics. The increase in the amount of Vitamin C was the main feature observed after thermal processing, followed by malic acid, choline, trigonelline, and acetaldehyde. On the other hand, thermal processing increased the amount of 2-furoic acid, a degradation product from ascorbic acid, as well as influenced the decrease in the amount of esters and alcohols. In general, the non-thermal processing did not present relevant effect on juices composition. The addition of prebiotics (inulin and gluco-oligosaccharides) decreased the effect of processing on juices composition, which suggested a protective effect by microencapsulation. Therefore, chemometric evaluation of the 1H qNMR and GC-MS dataset was suitable to follow changes in acerola juice under different processing.

Avaliação da metodologia microbiológica para determinação de 5-metiltetrahidrofolato em suco de caju (Anacardium occidentale L.)

Abstract Although cashew apple juice has been highly consumed in Brazil and several studies on its nutritional value have been published, no studies on the determination of folate contents in this juice were found in the literature. Several analytic techniques can be employed for the folate determination in foods. In this study, the microbiological assay using Lactobacillus casei was employed. Enzyme treatment and ultrasound waves were tested as pretreatment. The use of standards of folic acid and folate were also evaluated. The results showed that the enzyme treatment cannot be replaced by ultrasound treatment. The consumption of 200 mL of in natura cashew apple juice corresponds to a folate intake of 500 µg, which is higher than the recommended daily intake for adults. Keywords: cashew apple juice; folate; enzyme treatment; ultrasound; Lactobacillus casei. Resumo Embora o suco de caju seja bastante consumido no Brasil e muitos estudos sobre seu valor nutricional tenham sido publicados, a literatura nao reporta estudos sobre a determinacao de folatos nesse suco. Varias tecnicas analiticas podem ser utilizadas visando a deteccao da referida vitamina. Optou-se por utilizar o ensaio microbiologico oficial de determinacao de folatos em alimentos, utilizando-se