Therefore, there is great interest in increasing the amounts of isoflavone aglycones in soy products mainly because,
naturally, most of the isoflavones exist in the glycosylated forms (Cheng, Wu, Lin, & Liu, 2013). The enzymatic processing of isoflavone glycosides in soybean products using isolated β-glucosidases has proved to be effective in increasing the concentration of isoflavone aglycones (Horri et al., 2009, Xue et al., 2009 and Yang et al., 2009). It has previously been demonstrated that the use of the immobilised microorganism cells containing enzymes of interest in bioconversion processes is advantageous when compared to the selleck screening library use of the purified enzymes, since the purification step is not necessary and enzymatic stability is higher (Junior et al., 2009). Debaryomyces hansenii is the most common yeast species in protein-rich fermented food, where this
species metabolises organic acids and amino acids to regulate the acidity, and also PLX3397 in vitro provides lipolytic and proteolytic activities that contribute to flavor development; the potential of D. hansenii UFV-1 to produce hydrolytic enzymes, specially α-galactosidases, has previously been explored ( Viana et al., 2007). The present study reports the purification and characterisation of an intracellular β-glucosidase from D. hansenii UFV-1, the immobilisation of D. hansenii cells in calcium alginate, and the application of the free and immobilised enzymes for the hydrolysis of isoflavone glucosides in soy molasses. The yeast strain used in this study Mannose-binding protein-associated serine protease was isolated from a dairy environment
in Minas Gerais, Brazil, and maintained in the culture collection of the Laboratory of Microorganism Physiology, BIOAGRO, Federal University of Viçosa (UFV), Brazil. The yeast was identified by the Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands, as D. hansenii (Zopf) Lodder & Kreger-van Rij var fabryi Nakase & Suzuki. In this study it is designated as D. hansenii UFV-1. A stock culture of D. hansenii UFV-1 was maintained at −80 °C in glycerol and YPD medium (1% yeast extract, 2% peptone and 2% glucose). D. hansenii UFV-1 was streaked on an YPD agar surface (1.5% agar) and maintained in an incubation chamber at 30 °C for 36 h. The yeast was then activated in YPD liquid medium and incubated for 12–15 h, 180 rpm at 28 °C. The cells obtained after centrifugation (5000g for 5 min at 4 °C) were inoculated in an YP medium (1% yeast extract, 2% peptone) containing cellobiose, glucose, maltose or cellulose (1%) as the carbon source. After incubation at 28 °C, 180 rpm, for 12, 24, 36 and 48 h, the supernatant was separated by centrifugation (15,000g for 20 min at 4 °C) and the biomass was utilised as a source of the intracellular enzyme.