From Charcuterie to Plant-Based: Harnessing Penicillium nalgiovense for Innovative Soybean Co-Culture Fermentation

Improving the flavour of soybean-based ingredients remains challenging as soybeans naturally contain compounds that generate green and beany notes. This study evaluated how the surface-growing food-grade fungus <i>Penicillium nalgiovense</i> (PN), alone and together with selected yeasts and lactic acid bacteria, alters the chemistry and sensory attributes of soybeans during solid-state fermentation. PN showed strong proteolytic activity in the monoculture fermentation, producing the highest accumulation of free amino acids (1324 mg/100 g), while its combination with <i>Lactiplantibacillus plantarum</i> (LP) further increased this to 1487 mg/100 g due to acid-assisted protease action. Sugar and organic acid profiles reflected distinct metabolic roles among the strains; for example, PNLP and PN-<i>Debaryomyces hansenii</i> (DH) depleted sucrose and glucose completely by 72 h, whereas DH retained substantial sucrose. Fermentation also altered the lipid profiles, where PN-<i>Kluyveromyces marxianus</i> (KM) showed the highest increase in polyunsaturated fatty acids, with linoleic and α-linolenic acid increasing more than twofold and threefold, respectively. Volatile analysis showed a significant decrease in hexanal (from 18.3 µg/g in control to <2.0 µg/g post fermentation) and an increase in esters, floral alcohols, and savoury compounds depending on the microbial pairing. Electronic tongue profiling showed that PN-fermented samples produced the strongest savoury taste signals. Overall, the work highlights how specific PN-yeast or PN-LAB combinations can be used to modulate flavour development in fermented soy-based substrates.