Thiamine-producing lactic acid bacteria and their potential use in the prevention of neurodegenerative diseases.

Thiamine or vitamin B1, an essential micronutrient mainly involved in energy production, has a beneficial impact on the nervous system, and its deficiency can be associated with the development and progression of neurodegenerative diseases. The aim of this work was to select thiamine-producing lactic acid bacteria (LAB) and study their physiological effects using neuron cell cultures. In this study, 23 LAB able to produce thiamine were identified by growth in thiamine-free synthetic medium. Intra- and extracellular thiamine concentrations were determined using a microbiological method and results confirmed by HPLC techniques. A wide variation in vitamin production was found showing that this property was not only species specific but also a strain-dependent trait. Five of these strains were pre-selected for their capacity to produce higher concentrations of thiamine. Only the pre-treatment with the intracellular extract of Lactiplantibacillus (L.) plantarum CRL 1905 increased significantly neuronal survival in N2a cells' model of neurotoxicity (MPP ⁺ ) with thiamine deficiency conditions (amprolium). Furthermore, amprolium-resistant variants of CRL 1905 were isolated by exposition of the strain to increasing concentrations of this toxic thiamine analogue. The variant A9 was able to increase more than 2 times the intracellular thiamine production of the original strain. A9 bacterial extract significantly prevented neuronal cell death and the increase of IL-6. The amprolium-resistant strain A9 showed a modulating and neuroprotective effect in an in vitro model of neurotoxicity constituting a potential bio-strategy to counteract thiamine deficiencies and thus prevent or treat neurodegenerative diseases. KEY POINTS: • LAB can produce thiamine in a species- and strain-dependant manner. • L. plantarum CRL 1905 significantly reduce MPP ⁺ -induced neurotoxicity in N2a cells. • Amprolium-resistant strain A9 has neuroprotective effect and prevents IL-6 increase.