Bioprospecção de bactérias do gênero Lactobacillus presentes no leite cru da microrregião de Toledo-PR visando valorização de sua indústria queijeira

Abstract

This interdisciplinary study addresses the bioprospecting of Lactobacillus strains in raw milk from the Microregion of Toledo, Paraná, aiming to enhance the local cheese industry. It should be noted that this work is an integral part of the Biopark's fine cheese project, and aims to improve the region's dairy basin by bioprospecting native Lactobacillus strains with a view to their application in cheese production. When considering Geographical Indications (GI), the aim is to improve the quality of cheeses and contribute to regional economic and cultural development. The absence of a specific geographical indication for cheeses in the region opens up space for the identification of the microbiota present in locally produced milk samples. The development of the work included isolating, morphologically and biochemically evaluating, selecting and genetically identifying strains of Lactobacillus with potential for cheese production from raw milk samples obtained from ten different producers. This study not only contributes to the appreciation of local products, but also offers a sustainable perspective for rural development, aligned with global trends in valuing the origin and preservation of traditional food practices. The methodology included several microbiological, biochemical and genetic analyzes to characterize the isolated strains, such as catalase test, Gram staining, motility test, lactose fermentation test, tolerance tests at 1%, 3%, 5% and 7% (m/v) of NaCl, CO2 production test from glucose, tolerance test at temperatures of 15°C, 40°C and 45°C and sugar fermentation test. According to the results obtained, of the 250 microorganisms initially isolated, 110 showed growth on MRS agar under the conditions used, and possible explanations for the lack of growth were discussed. The selection process resulted in 68 catalase-negative strains, then 55 Gram-positive ones and sequentially 41 characterized as bacillus. The motility test reduced it to 28 strains, of which 26 were capable of fermenting lactose. All 26 strains were able to tolerate 1% NaCl, but this number reduced to 22 at 3% and to 13 at 5%. Of the 13, eight showed efficient fermentation at 7% and the other 5 showed weak fermentation. The 13 strains also presented homofermentative characteristics, that is, capable of forming only lactic acid, without other byproducts, ideal within this context. Subsequent tests included tolerance to different temperatures and sugars and carried out a better metabolic characterization of the selected strains. In the end, it was found that all 13 strains presented favorable results, highlighting their viability for use in the cheese industry. Although the tests have enabled inferences about possible species, identification requires molecular analysis, given the intrinsic diversity of the strains. Finally, it is highlighted that the results of the present study contribute to the selection of promising Lactobacillus strains for cheese production in the Microregion of Toledo-PR, as well as their possible industrial applications, highlighting the importance of more in-depth molecular investigations for a complete characterization.