Utilização do yacon (Smallanthus sonchifolia) para estudo de seus açucares e como fonte de invertase : purificação e caracterização de invertase extraida do yacon

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Yacon is an Andean root, rich in fructooligosaccharides, and easy to grow. It contains great amount of sugars, and evidence of the presence of enzymes of the beta-fructofuranosidase type, such as invertases, in its metabolism. Yacon (Smallanthus sonchifolia) roots were harvested and stored under different conditions. The sugar contents and invertase activity of these roots were followed. The greatest changes in the sugar contents occurred with fructose and 1-kestose. The enzymatic activity varied with the different storage conditions, and the maximum activity was after 15 days storage at 4°C. The sugar concentrations varied a lot, and the highest sugar concentrations were found for fructose and 1-kestose. All the sugar concentrations increased during the different storage conditions and times. Enzymes of the type p-fructofuranosidase were extracted from yacon. The extraction optimization was accomplished using different buffers, different pH values and different types of protein precipitation. The enzymatic extract was biochemically characterized, showing an optimum pH of 5.5, optimum temperature of 40° C and the following kinetic parameters: Km= 0.0258 and Vmax = 0.1265. The extract presented invertase activity, detected by the production of reducing sugars from the enzyme reaction. The enzymes showed pH stability between 5,0 and 5,5, and temperature stability between 25° C and 40° C. The yacon invertases were semipurified and characterized. The chromatographic profile and SDS-PAGE indicated the presence of isoforms in the final fraction of the purification, as well as its behavior with respect to temperature and pH. The optimum pH of the semipurified invertase was 5.5 and the optimum temperature was 60° C. The molecular weight of the invertase was 68 Kda, determined by eletroforese SDS/PAGE and gel filtration in Sephacril S-200. The enzyme presented low stability to pH, and temperature stability only between 30° C and 40° C

ASSUNTO(S)

carboidratos invertase

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