Feather Waste Biodegradation and Biostimulant Potential of Gordonia alkanivorans S7: A Novel Keratinolytic Actinobacterium for Sustainable Waste Valorization

The poultry industry produces significant quantities of keratin-rich waste, primarily feathers, whose traditional disposal methods-incineration or chemical treatment-result in environmental damage and resource depletion. This research introduces a sustainable biotechnological method for the valorization of feather waste utilizing <i>Gordonia alkanivorans</i> S7, an actinomycete strain extracted from petroleum plant sludge. This is the inaugural publication illustrating keratinolytic activity in the <i>Gordonia</i> genus. The optimization of the degradation process via the Taguchi approach led to the effective biodegradation of untreated home chicken feathers, achieving dry mass loss of up to 99% after 168 h in a mineral medium. The agricultural potential of the obtained keratin hydrolysate, which was high in organic components (C 31.2%, N 8.9%, H 5.1%, and S 1.7%), was assessed. Phytotoxicity tests demonstrated that the feather hydrolysate led to better growth of the indicator plants-<i>Sorghum saccharatum</i> and <i>Lepidium sativum.</i> The highest values of root growth stimulation were 26% for <i>S. saccharatum</i> and 31% for <i>L. sativum</i>, at a dose of 0.01%. Shoot growth stimulation was noted only for <i>L. sativum,</i> reaching 38% (0.01%), 53% (0.05%), and 37% (0.1%), as compared to the control sample. These results demonstrate the process's combined economic and environmental benefits, providing a fresh approach to the production of bio-based plant biostimulants and sustainable keratin waste management.