Sustainable production of plant biostimulants from cephalosporin fermentation residues: Ultrasonic dissolution and enzymatic hydrolysis

Abstract

Cephalosporin fermentation residues (CFR) is one of the most challenging industrial organic wastes due to their high nitrogen content. To transform the waste into high-value products, this study explored the effects of various factors on the solubility of total nitrogen (TN) and amino acids (AAs) and the enzymatic hydrolysis characteristics of proteins in CFR and evaluated the bioactivity of the hydrolysates through soybean germination experiments. Results showed that the solubility of AAs and TN reached their peaks at pH = 12 and 50℃, and ultrasonic treatment for 4 h further improved their dissolution. After 24 hours of hydrolysis, the AA yield in the group combining ultrasonication and enzymatic hydrolysis reached 217.5 g/kg dry matter, an 8 % increase compared to the control. The contents of some AAs, such as glutamic acid, phenylalanine, histidine, and arginine, increased by 43–85 % in the hydrolysate. Fluorescence spectroscopy confirmed the release of aromatic amino acids, such as tryptophan and tyrosine, which are known to improve plant stress tolerance. Furthermore, the diluted hydrolysates significantly promoted soybean seed germination under cold and saline conditions (P < 0.05), with the highest germination rates observed at a 1000x dilution. These findings highlight the effectiveness of enzymatic hydrolysis in transforming CFR into plant biostimulants, offering a sustainable solution for agricultural and environmental applications.