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Effects of Rhizopus oligosporus-Mediated Solid-State Fermentation on the Protein Profile and α-Glucosidase Inhibitory Activity of Selenium-Biofortified Soybean Tempeh

Summary

Researchers developed a special tempeh (traditional soybean food) enriched with selenium using a fungus called Rhizopus oligosporus. The selenium-enriched tempeh had improved protein quality with more amino acids and demonstrated strong ability to slow down sugar absorption in the digestive system, similar to diabetes medications. This makes selenium-biofortified tempeh a promising natural functional food for managing blood sugar levels while providing essential selenium nutrients that many people lack.

Background

Selenium deficiency affects approximately 1 billion people worldwide. Solid-state fermentation using Rhizopus oligosporus offers a promising strategy to enhance the nutritional quality of legumes while biotransforming inorganic selenium into organic forms with superior bioavailability.

Objective

This study evaluated how Rhizopus oligosporus-mediated solid-state fermentation of selenium-biofortified soybean tempeh affects fungal growth, protein profile, amino acid composition, selenium speciation, and α-glucosidase inhibitory activity at varying concentrations of selenate and selenite (0-60 mg kg⁻¹).

Results

Selenate at 42 mg kg⁻¹ significantly increased flavor amino acids, essential amino acids, and total amino acids, while selenite showed minimal improvement. Selenate biofortification converted to selenomethionine (56.2%) and Se(VI) (21.4%), while selenite converted to multiple organic forms including selenomethionine (56.2%), selenocystine (20.4%), and methylselenocysteine (7.5%). Se-enriched tempeh demonstrated potent α-glucosidase inhibition with IC₅₀ values of 1.66-2.89 mg mL⁻¹, superior to selenium-free tempeh (3.26 mg mL⁻¹).

Conclusion

Selenium fortification significantly influences R. oligosporus growth and metabolic activity, with selenate more effectively promoting amino acid release and selenite favoring organic selenium conversion. Se-biofortified tempeh demonstrates enhanced antidiabetic potential through α-glucosidase inhibition, positioning it as a promising functional food for glycemic management while delivering essential micronutrients.
  • Published in:Foods,
  • Study Type:Experimental Study,
  • Source: PMC12385420, PMID: 40870811, DOI: 10.3390/foods14162899
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