Induction of Transfructosylating Activity of Fructosyltransferase by Aureobasidium sp. ATCC 20524 in Two Step Batch Culture

SALINAS MARTÍN ANDRÉS; ME LUCCA,; NORA I PEROTTI

Orlando, USA

Congreso; 106st General Meeting (ASM-2006); 2006

ASM - American Society for Microbiology

Abstract Background. Fructooligosaccharides.(FOS) are mainly composed of 1-kestose (GF2), nystose (GF3) and fructosylnystose (GF4). They are considered as alimentary additives and nutraceutics. Several studies have demonstrated that prebiotic properties of these sugars favor the normal functioning of the digestive system. FOS are produced from sucrose by the action of fructosyl transferase (EC 2.4.1.9). The objective of this work was to produce fructosyltransferase by Aureobasidium sp. ATCC 20524 in submerged culture on bioreactor using sucrose as carbon source. Kinetic parameters of growth, fructosyltransferase enzymatic activity, and synthesis of FOS were studied. Methods. Bioproduction was carried out in a 1L stirred tank reactor in two steps. The initial volume was 800 mL with a sucrose concentration of 10 g/L. After 8 hs ,  200 mL  sucrose solution was added to obtain a final sucrose concentration of 200 g/L.  Sugars (sucrose, glucose, 1-kestose and nystose) were determined using HPLC. The transfructosylating activity and the hydrolytic activity were determined by measuring both the released reducing glucose and the released reducing sugars in a reaction mixture that consists of 80% w/v sucrose, 0.1 M citrate buffer pH 5.5 and  extracellular enzyme solution. Growth was determinated by measuring optical density. Results. Values of transfructosylating activity were higher than hydrolytic activity during the second step. Maximum values of  FOS production were: 102.4 g/L for 1-kestose and 59 g/L for nystose. Enzyme production was closely coupled to growth. Using Aureobasidium sp cells 150 g/L  FOS was produced from 200 g/L sucrose in the first day. In the stationary growth phase the yeast reach the value of  89 g/L of dry cell weight per volume. Conclusions. The use of the two step batch culture with this strain, allowing the microorganism to grow up before the induction with sucrose (second step), showed very high enzyme productivity, and its transfructosylating activity was higher compared to its hydrolyzing activity so this method is powerful  for  fructosytransferase and FOS production.