Use of fulvic acid-like compounds from pulp-derived black liquor for enhancing the selenium content of peanut buds

Background Cleaner production involving the extraction of useful material from the black liquor by-product of straw pulp would be environmentally beneficial and would permit increased wastewater usage. Results The fulvic-acid-like components of pulp black liquor (PFA) with molecular weights below 10 kDa were isolated. The chemical and physiological characteristics of PFAs were investigated. Selenite can enhance the selenium nutrition level of crops, but excessive selenite may be toxic to plant growth. In order to explore how to increase selenite tolerance and selenium accumulation in peanut, the effects of PFA on selenium-associated properties in peanut seedlings were examined by growing seedlings with sodium selenite (0, 5, 15, and 25 mg·L − 1 Na 2 SeO 3 , 15 mg·L − 1 Na 2 SeO 3 solution containing 60 mg-C/L PFA, and 25 mg·L − 1 Na 2 SeO 3 containing 60 mg-C/L PFA). Conclusion The results showed that with 15 mg·L − 1 Na 2 SeO 3 , PFA significantly increased both the total and hypocotyl fresh weight of the seedlings but reduced the fresh weight of the root. PFA also effectively promoted the conversion of Se from inorganic to organic compounds in the root and hypocotyl, increased the soluble total sugar and soluble protein contents of the hypocotyl, and thus improved the edible quality and food safety of the selenium-enriched peanut buds. The results suggest that PFA can be used as an innovative bio-based substance for selenium-enriched sprout vegetable production.