Assessing the Plant Growth-Promoting Potential of Diverse Feather Protein Hydrolysates Produced by Keratinolytic Bacteria

Poultry slaughterhouses generate substantial quantities of feather waste, posing potential environmental pollution. These feathers can be degraded by microorganisms, yielding amino acid-rich protein hydrolysates. This research aims to assess and compare the microbial degradation rates of feathers from chickens (CK), guinea fowls (GF), and pigeons (PG) for generating amino acid-rich hydrolysates for cowpea growth promotion. Feather-degrading bacteria were isolated from diverse sources, and their capacity to degrade feathers was evaluated by examining keratinase yields, degradation rate, and amino acid composition. Physico-chemical conditions were optimised using a one-factor-at-a-time approach to enhance keratinase yield, while the growth-promoting potential of the different hydrolysates on cowpea was assessed in a pot experiment in a screen house. The results revealed that Lysinibacillus sp., from the soil of a slaughterhouse dumpsite, completely degraded 1g/L of GF within 7 days, followed by CK and PG within 8 days. Following optimisation, the keratinase yield improved to 190 U/ml after the degradation of 2g/L of feathers under optimal conditions of pH 8 and temperature of 40°C. The hydrolysate derived from CK exhibited higher amino acid content compared to that from GF and PG, with the exception of alanine, which was more abundant in the GF hydrolysate. All the hydrolysates contained eight essential amino acids, which significantly enhanced various growth parameters of cowpeas, including root length, shoot length, root nodules, leaf area, chlorophyll and leaf numbers after four weeks of planting. The study suggests that Lysinibacillus sp. is a promising isolate for efficiently degrading feathers to produce protein hydrolysates, potentially aiding the growth of cowpeas.