Background
Feathers are the major byproducts of poultry industry and considered as waste. Feathers (composed of protein keratin) are metabolized by a number of microorganisms as a source of carbon and nitrogen. Degradation of feathers results in production of amino acids and peptides, which can be employed as precursors for plant growth-promoting metabolites such as indole acetic acid, ammonia and HCN. The aim of the present investigation was to assess the influence of these metabolites (termed as feather protein hydrolysate) on plant growth promotion activity of keratinolytic bacterial strain Bacillus subtilis PF1.
Results
Strain PF1 exhibits potent keratinolytic activity and can efficiently degrade 10 g/l chicken feathers under submerged cultivation with 81.4 ± 4.40 U/ml keratinase activity. Different concentrations of feathers supported the production of indole acetic acid by strain PF1. Strain PF1 produces maximum indole acetic acid (46.2 ± 0.21 µg/ml) in the presence of 2.0 % feathers at 120 h of incubation. The indole acetic acid production was confirmed by thin-layer chromatography and Fourier transform infrared spectroscopic analysis. However, increased concentration of feathers exhibited negative effect on phosphate solubilization due to increased alkalinity. HCN production also exhibited positive correlation with concentration of feathers. Finally, plant growth of Vigna radiata in the presence of strain PF1 with chicken feathers in soil was investigated, which showed good plant growth promotion activity. Increased ratio of C/N in soil also supported the plant growth promotion activity of feathers.
Conclusion
Feather degradation property of B. subtilis PF1 could be efficiently utilized for feather waste management. The metabolites released by feather degradation along with strain PF1 could be successfully employed as an economic source of nitrogen fertilizers for plants.