Avaliação do potencial biotecnológico de bactérias láticas para produção de biomulsificantes, bacteriocinas e lipase

Abstract

Lactic acid bacteria (LAB) are a diverse group of microorganisms consisting of Gram-positive rods or cocci, generally recognized as safe microorganisms (GRAS). During fermentation, LAB produces bioactive metabolites, which have antioxidant, antidiabetic, antimicrobial, and emulsifying activities. Therefore, the present study aims to evaluate the biotechnological potential of lactic acid bacteria regarding the production of biosurfactants/bioemulsifiers, lipase and bacteriocins. Initially, four strains of LAB were screened for their ability to produce biosurfactants/bioemulsifiers (Lactobacillus acidophilus NRRL B-4495, Lactiplantibacillus plantarum NRRL B-4496, Lacticaseibacillus rhamnosus EM1107 and Lacticaseibacillus paracasei Shirota). The strain L. paracasei was selected to study the conditions for the production of biosurfactants/bioemulsifiers. Then, a central rotational composite design (DCCR) 22 was performed to evaluate the influence of glycerol concentration and initial pH on optical density at 600 nm (DO600 nm) and emulsification index after 24h (IE24%). Culture supernatants from L. paracasei were evaluated for antimicrobial activity (against Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 8739, Burkholderia cepacia ATCC 25416 and Burkholderia multivorans ATCC BAA-247), in vitro antioxidant activity and in vitro antidiabetic activity. Culture supernatants were also evaluated for the presence of lipolytic activity. In addition, a DCCR 2 3 was performed to evaluate the influence of lactose, peptone concentration and initial pH on bacteriocin production. The results showed that glycerol concentration and pH in the studied range did not interfere on optical density at 600 nm (DO600 nm). Regarding IE24%, the maximum response was obtained using 4.8% of glycerol and pH between 6 and 7. The antimicrobial activity test showed that the supernatants did not show activity against the tested strains. Remarkably high antioxidant activity was observed for both supernatants and the control (MRS), indicating the possibility of the presence of some interference in the culture medium. In addition, inhibitory activity for amyloglucosidase (20.7% to 23.9%) was observed. The presence of lipolytic activity was verified in the supernatants (16.12 and 19.00 U/mL). It was also verified that the variables peptone concentration, lactose, and pH positively influenced the production of bacteriocins by L. paracasei. Therefore, L. paracasei can be suggested as a viable source of metabolites with antidiabetic, antimicrobial (bacteriocins), bioemulsifying, and lipolytic activities.