Resumo

Nowadays the prebiotics production has gained interest due to its good properties to the bacteria in the lower part of human intestine. Among these the galacto-oligosacharydes have gained importance. They are obtained from lactose using &beta-galactosidase with high transglucosidation capacity. Yeasts and Actinomycetes, along with filamentous fungi, are among the microorganisms capable of producing this enzyme. The ideal system for economic galacto-oligosacharydes production is using cheap lactose source, microorganism with a rapid cell growth, extra-cellular &beta-galactosidase (preferably with high transglucosidation capacity) production and GRAS. This will allow the economic production of a hydrolisate with high GOS content. In this work the main objective was to evaluate 31 Yeast and 24 Actinomycetes strains from DPUA(UFAM) and URM(UFPE) collections in order to evaluate strains with ideal characteristics for &beta-galactosidase and GOS production. Yeast and Actinomycetes were grown in lactose rich medium containing 50 g/L of lactose, respectively at 28 and 30 oC for 3 and 5 days. Samples were taken at beginning and at the end of each growth. Each sample was centrifuged (3 500 rpm at 20 ºC) and the supernatant was collected and filter (0.22 micrómetros) for enzyme activity determination. One &beta-galactosidase Unit was defined as that quantity of enzyme that will liberate 1.30 mol/min of o-nitrophenol substrate at 30 ºC and pH 6.5. Final cell concentration was determined by reading the final O.D. at 600 nm and dry weight respectively for Yeast and Actinomycetes. The results showed that 24 out of 31 yeast strains were able to growth in rich lactose medium. Among all Yeast strains it was verified that Trichosporon cutaneum URM4789 had significant and rapid cell growth. The results of enzyme activity showed that &beta-galactosidase is intra-cellular. Among all Actinomycetes tested one strain of Streptomyces sp. growth very well and showed an extra-cellular &beta-galactosidase activity. This result will allow us a better definition of the strain that should be used for &beta-galactosidase and galacto-oligosacharydes production.