Bioprodução de β -(1→6)-D-Glucana e obtenção de derivado por carboximetilação visando atividade biológica

Abstract

The world market of polysaccharides has attracted large industrial companies interested in gaining new and profitable fields. Polysaccharides with technological and biological properties can be obtained from plants, algae and microorganisms. Among the polysaccharides with biological properties, glucans have been highlighted by demonstrate immunostimulatory activity and potential for treating diseases such as cancer, hypercholesterolemia, diabetes, multiple sclerosis and cardiovascular diseases. Recent studies demonstrate the production of exocellular β-glucans by filamentous fungi in submerged cultivations. Modifications in the chemical structure of glucans by carboxymethylation is considered an important route to improve its properties, may contribute to the increased solubility of the molecule as well as biological activities, especially those associated with antioxidant and antiproliferative mechanisms of action. Therefore, the present work aimed the production of β-1,6-D glucan (lasiodiplodana) by the Lasiodiplodia theobromae MMPI fungus in submerged cultivation and carboxymethylation of the molecule, characterization and evaluation of cytotoxicity and antioxidant activity. The carboxymethylation of the molecule was confirmed by checking specific chemical signals identified by FT-IR and NMR and 13C spectroscopy. Carboxymethylated molecule presented degree of substitution (DS) of 1.27. Thermal analysis (TG / DTA) indicated that native and carboxymethylated samples had four stages of mass loss. The first stage was at 125 ºC (loss of water) and there were two consecutive events of weight loss (200 ºC - 400 ºC) attributed to the degradation of the molecule. The fourth stage occurred between 425 ºC and 620 ºC (final decomposition) with exothermic peak at 510 ºC. SEM analysis indicated that the raw lasiodiplodan presents granular structures which are broken after carboxymetylation. XRD analysis showed that native and carboxymethylated biopolymers have no crystalline structure. Carboxymethylation aided to improve water solubility the molecule (60% increase) and to improve antioxidant activity assessed by ability to capture the ABTS, DPPH radical scavenging and the ferric ion reducing power (FRAP). There was no cytotoxic effect of raw lasiodiplodana and modified on the erythrocytes. The results suggest that the carboxymethylation of lasiodiplodan can contribute to improved biological properties and the potential biotechnological use of the molecule.