Kefir is a microbial complex capable of producing biofilms. This study aims to obtain biofilms associated with hydroethanolic extract of Euterpe oleracea Mart. (BEHEEo) as fixing method of recovery anthocyanins in kefir biofilm. Thus, BEHEEo formation kinetics was made at different concentrations of aqueous extract of E. oleracea, of kefir grains (KG) and of brown sugar (BS). Thereafter, macro and microelements of BEHEEo were determined; the rheological and structural characteristics were analyzed using atomic force microscopy (AFM), and anthocyanins dosage in BEHEEo was obtained. The best concentration of BS to form BEHEEo was 40 g/l with 100 ml of EHEEo (12.62±0.16 g), as well as a release of the BEHEEo anthocyanins occurring after 5 min (4.3±0.6 mg/100 g) with maximum peak at 60 min (20.8±0.3). The concentration of calcium iron and magnesium was 0.089, 0.1740 and 0.1808 mg/kg, respectively, indicating the concentration of Zn2+ which was 0.533 mg/kg. The AFM analysis revealed differences in the peaks of roughness depending on the concentration of kefir grains, with presence of Lactobacillus and yeast. The concentration of anthocyanins in BEHEEo two years after the incorporation was 26 mg/100 g. Therefore, it is suggested that the BEHEEo incorporating EHEEo anthocyanins has potential for therapeutic applications in several pathologies necessary for antioxidative processes.Key words: Biofilms, kefir, açaí, Euterpe oleracea Mart., anthocyanins, atomic force microscopy (AFM). INTRODUCTIONKefir is a beverage produced by fermenting substrates such as milk or sugar water by kefir grains (Rodrigues et al., 2005;Laureys and De Vuyst, 2014). The growth and the function of bacteria inside a population are crucial for their survival (Davey and O'toole, 2000). In kefir, there is a predominance of Lactobacillus which has high catabolic capacity and is complemented by yeast with high biosynthetic capacity.When growing kefir in water for more than twenty days, there is the formation of biofilms with therapeutic properties against pathogenic organisms. These biofilms are surfaces with a high rate of structural organization associated with bacterial colonies held together by a polymer secreted by their cells, which is called extracellular polymeric substance (EPS) (Watnick and Kolter, 2000, Donlan, 2002;Zhang et al., 2015). Among many strategies used for the study of biofilms, the one that is more highlighted is the use of the Atomic Force Microscopy (AFM), which allows measurement of the interaction forces between cells or cell-cell interactions (Dufrêne, 2015).One of the substances that have been intensified in recent years are the anthocyanins, due to their protective and healing properties. Anthocyanins have an important role in physiological functions related to human health (Lee et al., 2013). The antioxidant effect of anthocyanins have been known and proven fact. The action mechanism of the anthocyanin is inhibiting the free radicals that promote oxidation. The antioxidant agents capable of binding to the free radicals ...

The aim of this study was to investigate biofilm formation with kefir grains in the presence of soy extract. Kefir grains and soy germs at different concentrations were grown in the culture medium comprising brown sugar solution (40 gl-1) for 20 days. Biofilms that formed in this period were then removed and the pH of the culture medium were measured. Isoflavones of the medium of culture were extracted and quantified by high-performance liquid chromatography (HPLC). The superficial properties of the selected biofilms were analyzed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The culture medium after 20 days was found to have 19.59±3.57 µgl-1 of glycitein and 23.86±2.21 µgl-1 of genistein. The best concentration of kefir grains in order to extract isoflavone was 40 gl-1, with yield levels at 11.67 µgl-1 of glycitein and 17.78 µgl-1 of genistein. The analysis by AFM and SEM confirmed the increased roughness of the biofilm, dependent of the concentration of the amount of kefir grains. It is suggested that the biofilms incorporated the isoflavones and has potential for therapeutic applications in several pathologies wherein it is necessary the antioxidative processes.