Evolution and ecology of C30 carotenoid synthesis in Lactobacillaceae and application of pigmented lactobacilli in pasta production

Pasta is a staple food in many parts of the world. A bright yellow colour of pasta is preferred by consumers. However, the colour is easily degraded during pasta processing. In a sourdough used for pasta production, we identified the pigmented Fructilactobacillus spp. FUA 3913, which represents a novel species that remains to be described ,and carries genes for the carotenoid-producing enzymes CrtM and CrtN in its genome. HPLC and spectral analysis identified the carotenoid as 4,4'-diaponeurosporene which is also produced by other lactobacilli expressing CrtM and CrtN. The topology of the CrtM/N trees does not match the phylogeny of the organisms, indicating that the enzymes were acquired by horizontal gene transfer. Pigmentation is frequent in insect-associated lactobacilli and lactobacilli that are part of the phyllosphere. Pigmented heterofermentative lactobacilli may enhance the yellow colour of durum semolina pasta by two mechanisms, first, by producing carotenoids and second, by preventing lipoxygenase-mediated degradation of durum carotenoids during dough mixing and extrusion. The comparison of the influence of fermentation with the non-pigmented, homofermentative Lactiplantibacillus plantarum, the non-pigmented heterofermentative Fructilactobacillus sanfranciscensis and the pigmented, heterofermentative Fructilactobacillus spp. FUA3913 indicated that inhibition of lipid oxidation is more relevant for the colour of pasta. In summary, our study provides novel insights into the evolution of C30 carotenoid and ecology of lactobacilli, and documents the use of pigmented lactobacilli to enhance the yellow colour of fermented foods.