Viscosity of some polysaccharide solutions supports that these molecules can be applied in food sectors. Four exopolysaccharides (R1, R2, R3, R4) produced by different Rhizobium strains were selected. Sugar composition and differences in the uronic acid contents suggests that chemical structure of these molecules can vary when different culture conditions and strains are analyzed. The Power Law was the rheological model used to represent the experimental data of shear stress versus shear rate. All exopolysaccharides showed non-Newtonian behavior, with pseudoplastic characteristics. R1, R2 and R4 showed a slight increase in viscosity in the presence of 0,2 M NaCl.

A hexa-oligosaccharide was obtained by partial acid hydrolysis from botryosphaeran, an exopolysaccharide (EPS) β(1→3; 1→6)-D-glucan type, produced by the ascomyceteous fungus Botryosphaeria rhodina. The oligosaccharide was purified by gel filtration and charcoal-Celite column chromatography and the analysis was followed by HPAEC/PAD. The structure was determined by NMR spectroscopy and mass spectrometry, which showed that the oligosaccharide consists of six β-D-glucopiranosyl units O-6 substituted (gentiohexaose).

This article gives an overview of exopolysaccharides produced by fungi. The structural characterization of beta-D-(1->3) and beta-D-(1->3, 1->6)- glucans is discussed focusing on different chemical and physical procedures. The industrial applications are also considered mainly from the point of view of human health.

Bagaço de cana-de-açúcar foi utilizado como substrato para a produção de xilanase pelo Trichoderma harzianum Rifai, isolado previamente de peroba (Aspidosperma sp) em decomposição. Após ter sido lavado, seco e moído, o bagaço foi umedecido com meio mínimo de Vogel e autoclavado. Dois métodos de extração foram avaliados para recuperação da enzima: (A) Tween 80 0,1% em salina fisiológica (v/v) e (B) tampão acetato pH 5 (50mM) sob agitação (180rpm) durante 15, 30 e 60 minutos. Em média, foram recuperados 15U/ml de atividade xilanásica com ambos os extratores, após uma única extração, independente do tempo de agitação. Uma segunda e terceira reextrações recuperaram 10,4 e 6,6U/ml, respectivamente. O efeito de diferentes volumes de extração e a concentração de bagaço de cana para a produção da xilanase também foram investigados. A curva de crescimento de Trichoderma harzianum foi avaliada durante 20 dias e a maior atividade xilanásica (288U/ml) foi obtida no sétimo dia de cultivo. O extrato enzimático, após precipitação com sulfato de amônio, foi submetido à eletroforese em gel de poliacrilamida e apresentou 4 bandas de proteína, das quais apenas uma demonstrou atividade xilanásica.

Sugarcane bagasse was used as substrate for xylanase production by means of a strain of Trichoderma harzianum Rifai isolated from decaying Aspidosperma sp. (peroba) wood. The bagasse was washed, dried, milled and wetted with minimal salts medium and the cultures grown at 28 ± 2ºC for 7 days. Two extraction methods were tested for enzyme recovery: (A) Tween 80, 0.1% (v/v), in physiological saline, and (B) 50mM sodium acetate buffer, pH 5.0, under agitation (180rpm) for 15, 30 and 60min. After a single extraction, both extraction methods recovered an average of 15U/ml of xylanase activity, independent on the time of shaking. A second and third extraction recovered 10.4 and 6.6U/ml xylanase, respectively. The effect of volume size for extraction, and sugarcane bagasse concentration, on xylanase production were also investigated. The growth profile of Trichoderma harzianum was followed over 20 days on 14% (w/v) bagasse, and highest xylanase activity (288U/ml) appeared on the seventh day. The enzymatic extract after precipitation with ammonium sulphate was submitted to electrophoresis on polyacrylamide gels and showed 4 protein-staining bands, one of which exhibited xylanase activity.