الفهرس 
Biochemical studies on recycling of leather and okara wastes
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Abstract
Because of the great effectiveness of amino acids as naturally chelates for minerals, the present study was carried out to recycling of leather and okara wastes into their protein hydrolysates (LPHs and OPHs) by alkaline (CaO or KOH) or enzymatic (alkaline protease or trypsin) hydrolyses. Results showed that LPHs obtained by alkaline hydrolyses had the highest values for degree of hydrolysis (DH%), Fe2+-chelating activity and total free amino acids content, especially with CaO which recorded 46.86%, 85.37% at 3 æl hydrolysate and 16.45 mg/ml hydrolysate, respectively, while LPHs obtained by enzymatic hydrolyses showed the highest values as antioxidant and Cu2+-chelating activity especially with alkaline protease which recorded 66.35% at 700 æl and 75.55% at 800 æl hydrolysate, respectively. OPH obtained by CaO also revealed the highest values for DH%, Cu²⁺-chelating activity and total free amino acids content (4.65%, 97.68% at 800 æl hydrolysate and 0.51 mg/ml hydrolysate, respectively), while OPH obtained by KOH hydrolysis possessed the highest value for Fe²⁺-chelating activity (78.63% at 3 æl hydrolysate). OPH / trypsin 1% revealed the highest value as antioxidant (95.14% at 700 æl hydrolysate). On the other hand, LPH / CaO was used to prepare metal-protein hydrolysate chelates (Cu²⁺-, Zn²⁺- and Fe²⁺-LPHCs). Metal-LPHCs had antibacterial activities against E. coli, B. cereus and micrococcus spp. mostly with Zn-LPHC and Fe-LPHC. These complexes increased the growth characteristics and mineral absorption of spinach plants in hydroponic nutrient solution than that of mineral salts (CuSO₄, ZnSO₄ and FeSO₄). Cu-LPHC also increased the absorption of Cu (bioavailability) through everted gut sacs of broilers than of mineral salt CuSO₄