Genomic overview of Proteolytic Enzymes in Lactobacillus delbrueckii: Implications for Dairy Fermentation

ELEAN, MARIANO; ALBARRACÍN, LEONARDO; VILLENA, JULIO; SAAVEDRA, LUCILA; HEBERT, ELVIRA MARÍA

Rosario

Congreso; 13vo Congreso Argentino de Bioinformática y Biología Computacional, la 13va Conferencia Iberoamericana de Bioinformática y la 3ra reunión anual de la red RiaBio; 2023

A2B2C, RiaBio, SolBIo

Background: Lactobacillus delbrueckii is widely recognized as the primary starter culture in the dairy industry for the elaboration of a variety of fermented dairy products, such as yogurts, fermented sour milks, mozzarella, and Swiss and Italian cheeses. This group of microorganisms has a limited capacity to synthesize amino acids and is therefore dependent on the use of exogenous nitrogen sources for optimal growth. As milk contains only small amounts of amino acids and short peptides, Lactobacillus depend on a complex proteolytic system to obtainessential amino acids from caseins during growth in this substrate. The cell envelope proteinase (CEP) stands as a pivotal enzyme, initiating the hydrolysis of casein. Strain-specific differences in proteolytic activity have been observed, prompting an investigation into potential disparities in CEPs.Results: In this study, we analyzed the genomes of 27 L. delbrueckii strains. Despite all strains featuring a singular CEP gene, certain strains (KCTC 13731, NBRC 3202, and KCTC 3035) exhibited prematuretermination codons, leading to truncated proteinase variants. Two distinct proteinases were identified:PrtB in L. delbrueckii subsp. bulgaricus, and PrtL in L. delbrueckii subsp. lactis and L. delbrueckii subsp.delbrueckii. Remarkably, these proteinases shared over 95% amino acid identity, with L. delbrueckiisubsp. bulgaricus variants even surpassing 98% identity. Most amino acid substitutions maintained the conservative nature of the three-dimensional structure, including an unchanged catalytic triad. The comparisons identified syntenic blocks common among the genomes highlighting significantconservation surrounding the prt gene, particularly within L. delbrueckii subsp. bulgaricus and L.delbrueckii subsp. lactis. Additionally, sequence conservation was observed in the promoter region of the prt gene.The substantial conservation of the amino acid sequence of Prt and its promoters implies that disparities in activity among strains likely stem from regulatory variances. These variations might become evident through transcriptional, translational, or modulation of enzyme activity levels. Future research will aim to uncover these regulatory mechanisms.Conclusions: By shedding light on the proteolytic intricacies of L. delbrueckii, this research advances our comprehension of the microbial mechanisms underpinning dairy fermentation processes. These insights hold the potential to improve both the quality of dairy products and production efficiency.