Metabolic insights of lactic acid bacteria in reducing off-flavors and antinutrients in plant-based fermented dairy alternatives

Abstract

Multiple sensorial, technological, and nutritional challenges must be overcome when developing plant-based fermented dairy alternatives (PBFDA) to mimic their dairy counterparts. The elimination of plant-derived off-flavors (green, earthy, bitter, astringent) and the degradation of antinutrients are crucial quality factors highlighted by the industry for their effect on consumer acceptance. The adaptation of plant-derived lactic acid bacteria (LAB) species into plant niches is relevant when developing starter cultures for PBFDA products due to their evolutionary acquired ability to degrade plant-based undesirable compounds (off-flavors and antinutrients). Some plant-isolated species, such as Lactiplantibacillus plantarum and Limosilactobacillus fermentum, have been associated with the degradation of phytates, phenolic compounds, oxalates, and raffinose-family oligosaccharides (RFOs), whereas some animal-isolated species, such as Lactobacillus acidophilus strains, can metabolize phytates, RFOs, saponins, phenolic compounds, and oxalates. Some proteolytic LAB strains, such as Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus, have been characterized to degrade phytates, protease inhibitors, and oxalates. Other species have also been described regarding their abilities to biotransform phytic acid, RFOs, saponins, phenolic compounds, protease inhibitors, oxalates, and volatile off-flavor compounds (hexanal, nonanal, pentanal, and benzaldehyde). In addition, we performed a blast analysis considering antinutrient metabolic genes (42 genes) to up to 5 strains of all qualified presumption of safety-listed LAB species (55 species, 240 strains), finding out potential genotypical capabilities of LAB species that have not conventionally been used as starter cultures such as Lactiplantibacillus pentosus, Lactiplantibacillus paraplantarum, and Lactobacillus diolivorans for plant-based fermentations. This review provides a detailed understanding of genes and enzymes from LAB that target specific compounds in plant-based materials for plant-based fermented food applications.

Keywords: antinutrients; fermentation; lactic acid bacteria; off‐flavors; plant‐based alternatives.

FIGURE 1

Lactic acid bacteria (LAB) metabolic pathways involved in raffinose‐family oligosaccharides (RFOs), phytate, saponin, phenolic acid, oxalate, and enzyme inhibitor metabolisms. All enzymes are marked in bold. LacS (sugar transport permease), rafP (raffinose permease), levS (levansucrase), ftfA (levansucrase), melA (α‐galactosidase), phy (phytase), glu (β‐glucosidase), gal (β‐galactosidase), xyl (β‐xylosidase), ram (α‐rhamnosidase), gus (β‐glucuronidase), tan (tannase), lpdC (gallate decarboxylase), est_1092 (estA, feruloyl esterase), pad (phenolic acid decarboxylase), hcrB (flavocytochrome c), hcrF (FAD‐dependent oxidoreductase), par1/par2 (FAD‐binding reductases), frc (formyl‐coA transferase), oxc (oxalyl‐coA transferase), prt (envelope‐proteinase), opp (oligopeptide transport system), dpp (di‐/tripeptide transport system). Source: Created with BioRender.

FIGURE 2

Homology‐based blast analysis of genes (42) involved in the degradation of antinutrients to all QPS‐listed LAB species (240 strains). Gene and species abbreviations are included in File S1. (a) Species‐based clustered heatmap representing the average number of copies of genes found in the different LAB strains from each LAB species. (b) PC‐biplot (PC2 = 21.7% and PC1 = 28.0%) of the average number of genes found in each LAB species standardized to a scale of 0–1 based on the maximum LAB species representative of each antinutrient category. The five antinutrient categories were included as loadings, whereas each species was included as a score with a colored‐based dot scale. The closer the score (dot) is to the loading, the higher the number of species’ genes as an average of the representative strains analyzed from that species. EI, enzyme inhibitors; OX, oxalates; PA, phytate; PHE, phenolic compounds; RFOs, raffinose‐family oligosaccharides; SP, saponins. Source: Plots were created using OriginPro 2021.

FIGURE 3

Reductive–oxidative reaction of aldehyde volatile organic compound (VOC) off‐flavors to their carboxylic acids and primary alcohol forms through lactic acid bacteria (LAB) aldehyde (aldh) and alcohol (adh) dehydrogenases, respectively. NAD(P)H might mediate those reactions by acting as an electron donor or acceptor molecule. Source: Created with Biorender.