Selenium accumulation in protein fractions of Tenebrio molitor larvae and the antioxidant and immunoregulatory activity of protein hydrolysates

Although numerous types of organisms have been used to enrich selenium, a low-cost and efficient organism is yet to be identified. This study aimed to develop a new means of selenium enrichment using Tenebrio molitor larvae. Our results indicated that the total selenium content in larvae was increased 83-fold to 54.21 +/- 1.25 mu g/ g, and of this content, organic selenium accounted for over 97% after feeding the larvae with 20 mu g/g of sodium selenite. Selenium was distributed unequally in the protein fraction with following order: alkali-soluble protein bound selenium (36.32%) salt-soluble protein-bound selenium (19.41%) > water-soluble protein-bound selenium (17.03%) > alcohol-soluble protein-bound selenium (3.21%). Additionally, 81% of the selenium within the soluble proteins was distributed in subunits possessing molecular weights of < 40 kDa. After hydrolysis by alcalase, the protein hydrolysate of selenium-enriched larvae possessing 75% selenium recovery exhibited stronger antioxidant and immunoregulatory activities than those of regular larvae.