Bioprospecção de bactérias láticas isoladas do soro-fermento de queijo Porungo com potencial tecnológico

Abstract

Artisanal dairy products often harbor an unknown microbiota due to traditional methods and the use of milk from animals kept by producers. In light of this, elucidating the existing microbial structure through genome analysis serves as a strategy to uncover the types and abundance of present microorganisms. With the aim of isolating lactic acid bacteria with biotechnological potential from fermented whey used in the production of Porungo cheese, samples were collected from seven different production units. Whey samples were diluted and plated onto the surfaces of agar media including Man, Rogosa & Sharpe (MRS) agar, M17 agar, and Slanetz Bartley agar. This yielded 84 isolates, which were phenotypically characterized for morphology, Gram staining, catalase presence, and subjected to 16S rDNA gene sequencing for identification. Antimicrobial, proteolytic, and lipolytic activities were evaluated. Safety aspects, including hemolytic activity, DNase, and coagulase, were also examined. The biotechnological potential (growth, acidification capability, proteolytic and lipolytic activities) was assessed in eight selected isolates and utilized in the production of fermented milk. Of the 84 isolates obtained, the majority were Gram-positive bacteria in the form of cocci (91.7%) and cocobacilli (8.3%), with one catalase-positive isolate. The most prevalent genera found in the cheese fermented whey samples, as determined by 16S rRNA sequencing, were Streptococcus (51.2%), Lactococcus (27.4%), followed by Leuconostoc (5.95%), Staphylococcus (5.95%), Enterococcus (2.4%), Enterobacter (1.2%), and Pseudomonas (1.2%). 4.76% of the isolates were unidentified. Enhanced antimicrobial activity was observed in neutralized and centrifuged supernatants after 48 hours of incubation at 30 °C. Isolate QP60 (Lactococcus sp.) consistently exhibited robust results and inhibitory potential in the tests performed. Proteolytic activity was observed in 96.4% of the isolates, while only 13.1% demonstrated lipolytic activity. DNase and coagulase tests were negative in all isolates; hemolysis was absent in 59.5% of isolates, while 5.95% exhibited complete hemolysis and 34.5% showed partial hemolysis. Selected isolates assessed for biotechnological potential displayed lipolytic activity, and the most favorable proteolytic results were observed with isolates QP83 (Lactococcus sp.), QP40 (Lactococcus sp.), QP32 (Streptococcus sp.), and QP79 (Lactococcus sp.). Acid production potential, as evaluated by fermented milk pH determination, was highest in isolate QP40, reducing the pH from 6.8 to 4.6 in 10 hours. All samples exhibited an increase in titratable acidity. By day 15, isolate QP40 presented the highest acidity value and a growth of 7.4 log CFU/mL. This research holds significance as it presents novel findings on the microbiota within Porungo cheese fermented ferment. The biotechnological potential of Streptococcus and Lactococcus isolates, concerning antimicrobial, proteolytic, and lipolytic activities, displayed favorable outcomes, indicating that certain isolates hold promise for technological use and warrant further in-depth research endeavors.