Germination Study of Some Protein-Based Gels Obtained from By-Products from the Leather Industry on Tomato and Pepper Seeds

This study aimed to evaluate the biostimulant effects of three protein-based gels, GHC 1-B (20% gelatin (GPU-B) obtained by thermal hydrolysis from residual untanned leather and 80% collagen hydrolysates (HCE-B) obtained by alkaline-enzymatic hydrolysis from residual bovine-tanned leather), GHC 2-B (40% keratin hydrolysate (HKU-B) obtained by alkaline-enzymatic hydrolysis from sheep wool + 40% HCE-B + 20% GPU-B), and GHC 3-B (20% GPU-B + 80% hydrolyzed collagen (HPU-B) obtained by thermal and enzymatic hydrolysis from residual untanned leather). A germination study was carried out on pepper and tomato seeds at concentrations of 1%, 3%, and 10%. As a result of the study, it was found that all three protein-based gels showed a stimulatory effect on the tomato seeds at a 1% concentration, where the Gi (germination index) was ˂100%. The GHC 2-B variant had the highest stimulatory effect (Gi-190.23%). Pepper seeds have proven to be more sensitive to the gel's composition. The concentration at which it proved to be non-inhibitory (Gi-88.29%) was 1% in the case of GHC 2-B. It was found that the presence of hydrolyzed keratin in the composition can be a plus compared to the other two protein gels tested due to its composition, which is richer in phytonutrient compounds (e.g., sulfur molecules).