Lactobacillus rhamnosus

Lacticaseibacillus rhamnosus (Hansen 1968) Zheng et al. 2020 is the current valid name for the organism the trade still labels Lactobacillus rhamnosus; the basonym is Lactobacillus casei subsp. rhamnosus, and the type strain is ATCC 7469 = DSM 20021 = JCM 1136 = LMG 6400 = NCIMB 6375 = CCUG 21452. It is a Gram-positive, non-sporing rod of about 0.5-0.8 x 1-3 um occurring singly or in short chains, facultatively heterofermentative, and it is separated from the rest of the L. casei group by producing acid from rhamnose and by growing at 45 C while all strains also grow at 15 C. That wide growth window, together with well-documented acid and bile tolerance, is why the species survives spray-applied and refrigerated formats that defeat more fragile cultures. The reference strain of the species is GG, ATCC 53103, isolated in 1983 by Sherwood Gorbach and Barry Goldin, whose initials give the strain its name; the original 1985 patent filing described it as an L. acidophilus strain before it was reclassified. Comparative genomics of ATCC 53103 identified the spaCBA-srtC1 pilus cluster, whose SpaC tip pilin carries a mucus-binding domain - the structural feature most often cited when brands specify this species rather than another. Note that GG and other branded rhamnosus designations are proprietary and licensed by their owners. Thovek supplies documented non-proprietary strains with full deposit records as standard, states the designation on every certificate as FSSAI strain-level labelling requires, and can arrange licensed branded material where a customer's dossier calls for it. The commercial form is a freeze-dried culture concentrate on maltodextrin, blended to 100, 150, 200 or 300 billion CFU/g with overage so the declared count survives shelf life. Counts are made by MRS pour plate under anaerobic conditions at 37 C for 72 h, with ISO 15214 mesophilic lactic acid bacteria counting at 30 C or ISO 19344 | IDF 232 flow cytometry available where a buyer's method requires it. Because rhamnosus is frequently grown on dairy- or soy-containing media, allergen status is a lot-level declaration rather than a species property: Thovek quotes a dairy-free, soy-free plant-peptone grade separately for vegan and allergen-restricted formulations and never issues a blanket vegan statement against a dairy-media batch. The species is on the EFSA qualified presumption of safety list.