Table 2.
Anti-nutrients and potentially harmful compounds in SSF feedstocks and fungal biomass, and mitigation pathways enabled by solid-state fermentation (SSF).
| Compound | Foodstuff source examples | Effects on consumption | Example impacts of combining through SSF | References |
|---|---|---|---|---|
| Phytate | Brassica meals, cereals, okara, brans, spent grains, pomace, pseudocereals | Chelates Fe, Zn, Ca, Mg, lowering bioavailability | Fungal phytases (e.g., Rhizopus, Aspergillus, Pleurotus) produce phytases that hydrolyze phytate releasing bound minerals | (9, 22–24, 28, 41, 98, 115, 144) |
| Glucosinolates | Brassica meals (canola, mustard), cruciferous vegetables | Goitrogenic effects, thyroid dysfunction, bitter taste, reduced animal performance | Fermentation with Rhizopus oligosporus, Lactobacillus spp., or Bacillus spp. to hydrolyze glucosinolates into less harmful compounds | (28, 32, 35, 211) |
| Sinapine | Brassicas (Rapeseed, mustard seed, and others) | Bitter, astringent taste; reduced protein digestion; may cause allergic response | Solid-state fermentation with Trametes sp., Rhizopus oligosporus, or Bacillus subtilis degrades sinapine via laccase and other enzymes | (10, 23, 28, 32, 36) |
| Bound phenolics | Legumes, cereals (wheat), rapeseed, canola, quinoa, fruits, vegetables | Reduced protein/mineral bioavailability, astringency, reduced digestibility | Fermentation with Rhizopus oligosporus, Aspergillus niger, Pleurotus ostreatus, or Lactobacillus plantarum to release bound phenolics | (10, 33, 66, 85, 89, 115, 140, 141) |
| Tannins | Legumes, cereals, nuts, tea, fruits, vegetables | Reduced protein digestibility, astringency, toxicity at high intake | Fermentation with tannase-producing fungi (e.g., Penicillium glabrum, Aspergillus glaucus, A. niger, Rhizopus sppand others) to hydrolyze tannins | (Traka, 2016) (50, 78, 79, 113, 114) |
| Protease inhibitors/lectins | Legumes (soybeans, kidney beans, chickpeas), cereals | Inhibit digestive enzymes, reduce protein utilization, cause pancreatic hypertrophy | Fermentation with Rhizopus oligosporus, Aspergillus oryzae, Bacillus subtilis, or protease-secreting fungi to degrade inhibitors/lectins | (32, 50, 62, 63, 67, 77, 141, 143) |
| Allergenic proteins (β-conglutin) | Lupin seeds (Lupinus angustifolius, L. mutabilis), fungal/yeast biomass | IgE binding in sensitized individuals and allergenic reactions, immune hypersensitivity, reduce nutrient intake through increased excretion | Proteolysis during SSF reduces specific peptides; Fermentation with Rhizopus oligosporus, Propionibacterium spp., or protease-producing fungi to hydrolyze allergenic proteins (should be validated with immunoassays) | (3, 101–103) |
| Gossypol | Cottonseed meal or cake | Toxicity (liver, reproductive, cardiac), binds lysine | Solid-state fermentation with Candida tropicalis, Saccharomyces cerevisiae, Aspergillus niger, Pleurotus spp., or Paecilomyces variotii | (29, 32, 37, 84) |
| Saponins | Legumes (soybeans, chickpeas), quinoa, green microalgae | Bitter taste, hemolytic activity, reduced nutrient absorption | Fermentation with Rhizopus oligosporus, Aspergillus spp., Saccharomyces cerevisiae, or lactic acid bacteria to degrade saponins. SSF can alter saponin profile (sometimes reducing, sometimes increasing saponins); pre-washing/dehulling and post-processing are often required for reliable debittering. | (50, 210, 211 |
| Purines (nucleic acids) | Yeast-rich biomass, fungi, legumes | Uric acid load (hyperuricemia) for gout | Fermentation with Aspergillus oryzae, Blastobotrys adeninivorans, Candida utilis, or low-purine yeast strains; enzymatic degradation. Downstream RNA reduction is described by commercial operators using heat-shock to activate endogenous RNases as a standard mitigation step for fungal biomass intended for high intake. | (32, 34) |
| Chitin/Beta-glucans | Fungal biomass, mushrooms, yeasts, microalgae | Reduces apparent protein digestibility in vitro; Associated with indigestion; tough chewing texture; potential allergenicity | Fermentation with chitinase/β-glucanase-producing fungi (Mucor rouxii, Aspergillus terreus, Trichoderma spp.). Milling, alkaline/thermal pretreatments, or targeted enzymatic hydrolysis can further break down to improve digestion. | (58, 68, 73, 74, 109) |
| Mycotoxins | Contaminated grains, nuts, by products | Toxicity (carcinogenicity, nephrotoxicity, immunosuppression, reproductive toxicity); carcinogens, hepatotoxicity, immunosuppression | Fermentation with mycotoxin-degrading fungi (Rhizopus spp., a-toxigenic strains of Aspergillus spp.); laccase/peroxidase enzymatic detoxification (lactonases, peroxidases, laccases); Aflatoxin-degrading fungi (Trichoderma reesei, Aspergillus niger, Rhizopus spp.) | (3, 32, 195, 199) |
Effects of SSF are substrate-, strain-, and process-dependent. In some matrices, reductions in anti-nutritional factors or increased phytase activity do not necessarily translate into improved in vitro digestibility (143), and quinoa saponins may increase or decrease depending on processing conditions (Gautheron et al., 2024). Validate key endpoints analytically for the target substrate and product format.