Hafnia paralvei of dairy origin as a functional adjunct culture for in situ agmatine production in yoghurt-type products

Agmatine is a polyamine produced by the decarboxylation of arginine that has gained increasing attention due to its potential therapeutic applications, as it exhibits neuroprotective effects. Although agmatine has been commercially available as a supplement, its incorporation as an ingredient in the development of functional foods remains largely unexplored. Given the low levels of agmatine naturally present in foods, a promising strategy would involve the selection of an appropriate food matrix combined with the use of agmatine-producing strains, with suitable technological properties, during food processing. To this end, the effects of different technological factors on the ability of the dairy-origin strain Hafnia paralvei IPLA15029 to synthesise agmatine was evaluated. Agmatine production was enhanced at temperatures between 32 and 42 °C, under low oxygen availability, and was particularly favoured by acidic pH conditions. In addition, agmatine production was mainly detectable in the presence of a fermentable carbon source (glucose or lactose). Such source is required to achieve higher production levels, even when production is stimulated by acidic pH. However, high concentrations of these carbon sources, as well as those of sodium chloride, have an inhibitory effect. Analysis of agmatine synthesis throughout the growth curve revealed gradual agmatine-to-putrescine conversion, with complete depletion after 7 days. Taken together, these observations point to yoghurt-type dairy products as the most suitable matrix for agmatine accumulation. Indeed, using this strain for yoghurt-type products resulted in the highest agmatine accumulation reported in a dairy product (637 mg/kg), which remained stable during refrigerated storage.