Lactobacillus delbrueckii Group ☆

The Lactobacillus delbrueckii group consists of four subspecies: Lb. delbrueckii subsp. bulgaricus , Lb. delbrueckii subsp. lactis , Lb. delbrueckii subsp. delbrueckii , and Lb. delbrueckii subsp. indicus . The strains from the Lb. delbrueckii group form single or short chains of rods, have an optimum growth in milk between 40 and 45°C, and their DNA ranges from 49 to 51 mol% G + C. The Lb. delbrueckii group are obligately homofermentative lactobacilli and produce the D(−) isomer of lactic acid from a variety of carbohydrates. Strains from the Lb. delbrueckii group, and in particular Lb. delbrueckii subsp. bulgaricus , can produce exopolysaccharides (EPS) under different conditions. Lb. delbrueckii subsp. bulgaricus and Lb. delbrueckii subsp. lactis ferment lactose, can produce bacteriocins, and are commonly used in cheese manufacture. Lb. delbrueckii subsp. Lactobacillusbulgaricus is used extensively as a starter for yoghurt manufacture, establishing an associative growth with Streptococcus thermophilus . It is responsible of the production of many compounds that contribute to yoghurt flavor, such as acetaldehyde. Lb. delbrueckii subsp. delbrueckii does not ferment lactose and is not important in dairy products either as a starter or as adventitious bacterium.