Lactobacillus plantarum L-137
L-137 is a specific strain of the plant lactic acid bacteria Lactiplantibacillus plantarum, isolated from a fermented fish dish from Southeast Asia. It is most often used in heat-treated form, i.e., as a postbiotic rather than as a live probiotic.
What the strain designation means
In probiotic research, the strain is the relevant unit, not the species. Two strains of the same species can differ as much in characteristics as two entirely different species. The designation L-137 identifies a specific isolate, and research on L-137 says nothing about other plantarum strains.
The strain was isolated from plaa-som, a fermented fish dish from Southeast Asia, and has been studied in Japan for several decades.
Name change in 2020
The species Lactobacillus plantarum was reclassified in 2020 to Lactiplantibacillus plantarum, as part of a larger reorganisation of the genus Lactobacillus. Both names appear in literature and on labels, and refer to the same organism.
Heat-treated, not live
L-137 is normally used in heat-killed form, often written as HK L-137 following the English heat-killed. This is intentional: the entire research programme is based on the inactivated form. Such preparations are called postbiotics and fundamentally differ from probiotics, which by definition must contain live microorganisms.
Practically, this offers an advantage in shelf life — a heat-killed preparation does not lose viability during storage, which is a recurring quality issue for live probiotics.
Regulation
There is no EU-approved health claim for L-137. The EU has so far not approved any health claim for probiotics at all, and the word "probiotic" itself is considered a health claim in several member states.
