Superficial Characterization of Kefir Biofilms Associated with Açaí and Cupuaçu Extracts

Kefir is an acidic and low alcohol beverage obtained from the fermentation of milk at ambient temperature and, in form of biofilm, it can be used for several purposes, e.g., as an antimicrobial against a wide variety of gram-positive and gram-negative bacteria and against some fungi. However, some pharmaceutical applications require materials both antibacterial and antioxidant at same time. Herein, we obtain the first fundamental insights into the chemical production of antibacterial and antioxidant biofilms using brown sugar, kefir grains, acai (Euterpe oleracea Mart.) pulp and cupuacu (Theobroma grandiflorum Schum) pulp. Four essays were performed to obtain the biofilms, namely a without kefir film, a kefir biofilm, a biofilm of kefir with Cupuacu extract, and a biofilm of kefir with Acai extract. The crystallinity of the biofilms was analyzed using X-ray diffraction, which revealed a semicrystalline structure. These results were explained by the biofilms microstructure, which was analyzed by atomic force microscopy, demonstrating a growing dependence of roughness on the substrate concentration, mainly for the Cupuacu and Acai biofilms. The homogeneity of the surface of the biofilms was determined, revealing that all the biofilms have uniform distribution of heights on their surfaces. This research showed that the surfaces of the kefir, kefir with Acai extract and kefir with Cupuacu extract biofilms are characterized to be amorphous, without any diffraction peak associated with the crystal structure, and having high roughness, indicating that the films have good adhesion, and are uniform in the distribution of surface peaks, thus emphasizing that, once adhered to some surface, there will be no formation of bubbles on their surface. Therefore, considering their potential application in the pharmaceutical industry, the biofilms can be used as natural healing materials.