Structural evaluation of polymeric microbial films grown on kefir loaded with Maytenus rigida extract

Kefir is a probiotic that has several health promising properties. Its grains can form microbial films on different types of substrates. In the present work, the surface characteristics of kefir biofilms associated with Maytenus rigida Mart. extract were minutely studied. Three different concentrations of plant extract were included in the biofilm forming solutions, where fresh grains of kefir were inoculated. The results showed that the plant extract was successfully incorporated into the exopolysaccharide matrix of the biofilm. The main chemical components found linked to the plant extract were triterpenes. The crystallinity of biofilms increased with the addition of the plant extract. The morphology revealed that at low concentrations of the extract there was a prevalence of lactobacilli, while at high concentrations yeasts were more observed. Adhesion and wettability were higher for biofilm with less extract. These results revealed that a combination of plant extract and kefir's exopolysaccharide could form biofilms with chemical and topographic properties of great interest in regenerative medicine. A semi‐crystalline structure was observed for all biofilms as well chemical analysis revealed the presence of sugars and triterpenes. SEM and AFM showed that Bacteria were prevalent at low concentrations of Maytenus rigida. The biofilm loaded with 0.25 g/L of plant extract presented the most suitable values of adhesion and wettability.