Production of an enzymatic protein hydrolyzate from defatted sunflower seed meal for potential application as a plant biostimulant

•A direct enzymatic hydrolysis process was optimized on defatted sunflower meal.•A hydrolyzate rich in free amino acids and other bioactive compounds was obtained.•Amino acid profile was heterogeneous and complete.•The hydrolyzate assayed with the Audus test showed auxin-like activity.•The hydrolyzate was shown to promote root elongation on maize plants.