delbrueckii

Delbrueckii is the species epithet used in bacterial taxonomy, most prominently in the name Lacticaseibacillus delbrueckii, formerly Lactobacillus delbrueckii. The epithet honors Max Delbrück, a German‑American microbiologist. In current classifications, the genus Lactobacillus has been split, and Lacticaseibacillus delbrueckii is the accepted name for this species, which includes two subspecies: subsp. delbrueckii and subsp. bulgaricus.

Lacticaseibacillus delbrueckii belongs to the family Lactobacillaceae, order Lactobacillales. It is a Gram-positive, non‑spore‑forming rod that ferments sugars to lactic acid. Many strains are homofermentative, producing lactic acid as the main end product. The reclassification in 2020 separated this species from the core Lactobacillus genus, reflecting phylogenetic distinctions recognized by contemporary taxonomy.

The two subspecies have distinct associations and properties. Subsp. bulgaricus is well known as a thermophilic, dairy-adapted bacterium used in yogurt starter cultures, typically in combination with Streptococcus thermophilus. Subsp. delbrueckii occurs more broadly in dairy environments and plant materials and can contribute to fermentation processes and flavor development in various foods. Both subspecies participate in proteolysis and peptide release that influence texture and aroma in fermented products.

Applications and significance: Lacticaseibacillus delbrueckii strains are important in dairy fermentation, especially yogurt production, and some strains are explored for probiotic potential. They are routinely used as part of starter cultures and are subject to food-safety and regulatory evaluations in different jurisdictions.