Bactérias degradadoras de lactose e glúten presentes em queijos e iogurtes encontrados no mercado de Manaus: alternativas para a intolerância à lactose e à Doença Celíaca

Abstract

Microorganisms are of fundamental importance for maintaining the equilibrium of living organisms and the chemical elements of our planet. They occur in all nature environments, including in foods. Several researches have shown that microorganisms found in the oral cavity and intestines have the ability to degrade components found in milk (lactose) and in some cereals (gluten). This work had as objectives, to isolate, purify and morphologically characterize cheeses and yoghurt bacteria commercialized in the city of Manaus, Amazonas, as well as to test their crude extracts capable of degrading lactose and gluten, aiming as an alternative to minimize or solve the problem of lactose intolerance and Celiac disease that affect part of the world population. Seventy-five bacteria were isolated from the 10 types of cheese and 10 types of yogurts used for the tests. All 75 bacteria showed high growth in the first 24 hours of evaluation in both culture media tested (gluten or lactose). Of the 75 bacteria tested, 61 presented halo formation of degradation in medium containing gluten. For the Gluten Degradation Index (GDI), of the 61 bacteria evaluated, 22 did not present GID during the test, 30 had GIDs considered low, 9 GIDs were considered medium and none had GID considered high. The carbon source of the culture medium (gluten or lactose) influenced the morphological characteristics of the colonies of the 20 selected bacteria as the best ones. In the Gram staining test, 16 bacteria were Gram Negative and four Gram positive. Of the 13 bacteria used in the genetic characterization, it was possible to identify only four at the species level. Four isolates are of the genus Pseudomonas, four of the genus Bacillus, two of the genus Stenotrophomonas, one of the genus Brevibacillus, one of the genus Achromobacter and one of the genus Burkholderia. In order to evaluate twelve bacteria selected from previous tests, laboratory experiments were performed in a liquid medium containing lactose or gluten as a source of carbon at pH of 2.3 (similar to that of the stomach) and 8.0 (similar to that of the intestines) at temperatures of 37 ° C and 55 ° C. The bacteria BLG01 (Pseudomonas sp.), BLG02 (Bacillus sp.), BLG06 (Pseudomonas sp.), BLG16 (Stenotrophomonas maltophilia), BLG25 (Stenotrophomonas sp.), BLG28), BLG38 (Bacillus sp.), BLG45 (Burkholderia sp.), BLG52 (Brevibacillus parabrevis), BLG56 (Achromobacter sp.) and BLG73 (Bacillus sp.). showed potential to be used as probiotics after future confirmation of non-pathogenicity or as suppliers of enzymes capable of degrading lactose and gluten. All bacteria showed sensitivity to acidity and alkalinity equivalent to those of the human stomach and intestines, indicating that this acidity/alkalinity bipolarity can be a defense mechanism of the human organism against the action of pathogenic or undesirable bacteria. For desirable bacteria to be used as probiotics, they need to be ingested at high concentrations, above 106 células.mL-1. From the 12 bacteria tested, those with the highest potential for use as probiotics, if not pathogenics, are BLG28 (Bacillus sp.), BLG38 (Bacillus sp.), BLG45 (Burkholderia sp.), BLG52 (Brevibacillus parabrevis), BLG56 (Achromobacter sp.) and BLG73 (Bacillus sp.), since they are part of genera with little possibility of pathogenicity and because they present positive growth in the first two hours at pH 2.3, similar to that of the stomach. However, they need to colonize and participate of the intestinal flora, and to help to the lactose and gluten metabolism ingested as food. To evaluate if the carbon source and the growth phase of the bacteria affect the production and quality of proteases capable of degrading gluten, experiments were carried out on the crude extracts of nine bacteria, BLG02, BLG25, BLG28, BLG33, BLG38, BLG45, BLG52, BLG56 and BLG73. The extracts were obtained from culture of these bacteria in two culture media (gluten and lactose as carbon sources) and collected with 6, 12 and 24 hours of incubation. Dilutions of the extracts were also tested for their ability to degrade gluten. All bacteria produced extracts with the ability to break down gluten. The source of carbon (lactose or gluten) has affected the ability of these bacteria to produce extracts capable of degrading gluten. The majority of them produced more proteases when growing in the medium with this proteic complex. The time of collection of bacterial extracts also influenced their ability to degrade gluten, with the 24 hour extracts from most of these bacteria showing the highest degradability when comparing with those produced with 6 and 12 hours. The highest percentage of gluten degradation was 87.3% using the extract obtained with 24 hours of growth of bacterium BLG56 (Achromobacter sp.) grown in culture medium containing gluten. Based on the degradability, collection times of bacterial extracts and culture media, it can be concluded that the nine bacteria present different proteases capable of degrading gluten. This ability to degrade gluten varied with their concentrations in the solution in different ways and this feature may serve as an additional test to differentiate one from the other. More detailed studies, such as the purification of the extracts components of these bacteria, are needed to evaluate each of these proteases individually to choose the best with biotechnological potential.