Potencial probiótico de bactérias láticas isoladas de leite caprino: aspectos de segurança e funcionalidade

Abstract

The Lactic bacteria are important microorganisms from the technological point of view, since they are widely used in the fermentation of dairy products. In addition, they have the ability to improve shelf life, safety, nutritional value and product quality. They may present probiotic potential and desirable antimicrobial activity for food preservation, as well as the production capacity of exopolysaccharides (EPS). The objective of this research was to evaluate the probiotic potential of lactic acid bacteria isolated from goat milk for its use as a functional ingredient in different food products. For this evaluation, some aspects of safety and functionality, including exopolysaccharide (EPS) production capacity, were considered. Furthermore, the antimicrobial activity of the isolates was evaluated against the microorganisms that promote caries. Thus, the specific objectives were to characterize the safety aspects of lactic bacteria, verify their proteolytic activity, evaluate and characterize their EPS production capacity. For this, safety studies (hemolytic activity, gelatinase production, coagulase and sensitivity to antibiotics) were performed, and functionality was considered considering EPS production, proteolytic activity, autoaggregation, gas production, survival through passage through the gastrointestinal tract ) and antimicrobial activity against bacteria of importance for oral health. The characterization of the EPS the isolate Lactobacillus plantarum DF60Mi was performed through structural analyzes and composition (thermogravimetric analysis, infrared spectroscopy, carbohydrate composition, protein determination, total sugar and antioxidant activity) was performed. Isolates were safe (negative β-hemolytic activity, no gelatin hydrolysis and coagulase production, sensitivity to antibiotics: ampicillin, gentamicin, chloramphenicol, tetracycline and clindamycin). There was no proteolytic activity as well as gas production from glucose and the isolates presented high percentage of autoaggregation (84.24% ± 3.77 to 93.38% ± 0.06). Isolates LS2, LS3 and DF04Mi showed greater resistance to the acidic condition in the survival simulation tests when the TGI passed in the compartment corresponding to the stomach when compared with the others. Isolates DF04Mi and DF60Mi showed remarkable resistance after 4 h and 6 h of incubation in the small intestine compartment. The performance presented by isolates allows them to be considered as possible probiotic candidates. We highlight L. plantarum (DF60Mi) and Lactococcus lactis (DF04Mi) with potential to be used in the fermentation of foods, as well as antagonists against the microorganism related to the development of caries (Streptococcus mutans ATCC 25175) and, therefore, used for the benefit of oral health. L. plantarum (DF60Mi) produced EPS both in the fermentation in skim milk containing glucose and sucrose. The EPS presented thermal resistance, starting to decompose at around 250 ° C. EPS were characterized by infrared spectroscopy and mass spectrometry by the Maldi-TOF-MS technique as possibly heteropolysaccharides α-D-glucans. In addition, an article was developed to review the literature on the technological properties, biological activity and potential of exopolysaccharides produced by L. plantarum for application in the food industry.