Induction of phytochemical glyceollins accumulation in soybean following treatment with biotic elicitor (Aspergillus oryzae)

• Glyceollins accumulated in response to stress and biotic elicitors in the soybean seeds.
• Aspergillus oryzae Lu brewing 3042 elicitation of soybeans altered metabolite profiles.
• Aspergillus oryzae Lu brewing 3042 treatment increased contents of glyceollin and coumestrol.
• Results emphasized the importance of careful selection of fungus for specific soybean variety.

The different isoflavonoid phytoalexins produced by soybeans are known to possess antioxidant and estrogenic effects, with potential health benefits in humans. Enhanced production of phytoalexins by soybean plant will help in research efforts. In this study, the effects of stress induced by Aspergillus oryzae Lu brewing 3042 on the composition of wounded surface of Nigerian soybean seeds were analyzed. Glyceollin, one of the inducible phytoalexins produced by plants, were induced in the Nigerian soybeans variety through fungal infection. Glyceollins I, II, and III were separated by preparative high performance liquid chromatography (Prep-HPLC) from other phytochemicals and had purity of 97.5%. Results from the time course study indicated that the maximum concentration of glyceollins, 0.74 mg/g, occurred at day 3 in the soybean cotyledons inoculated with A. oryzae Lu brewing 3042. The soybean seeds soak time in water was examined and a suitable soak time of 4 h was found best in the accumulation of glyceollins after the soak time study was conducted. Cut or wounded surface of soybean cotyledons produced glyceollins upon fungal treatment as elicitor and the glyceollins were confirmed by the ultra performance liquid chromatography–mass spectrometry (UPLC–MS). Analysis of elicitor-treated Nigerian soybean extract showed that A. oryzae Lu brewing 3042 treatments achieved maximum concentration of phytoalexin glyceollins at 1.32 mg/g extract dry weight. These results indicate that using food-grade A. oryzae Lu brewing 3042 elicits the biosynthesis of phytoalexins, alters the secondary metabolite profiles of the soybeans and offers enhanced bioactivity of soybean as a functional food ingredient.