Proteolytic system of Bacillus sp. CL18 is capable of extensive feather degradation and hydrolysis of diverse protein substrates

ABSTRACT

1. Feathers are recalcitrant protein-rich wastes produced in huge amounts by poultry processing for meat production. Hence, feather bioconversion and protease production by Bacillus sp. CL18 were investigated.

2. Bacillus sp. CL18 demonstrated a remarkable feather-degrading potential. Through cultivations on feather broth (10 g l⁻¹ feathers), 94.5% ± 3% of whole feathers were degraded after 4 d. Increases in soluble protein contents were observed and protease production was maximal also at d 4. This strain produced diverse proteolytic enzymes during growth.

3. Crude protease displayed optimal activity at 55°C (50–62°C), pH 8.0 (7.0–9.0) and a low thermal stability. Proteolytic activity increased in the presence of Ca²⁺, Mg²⁺, Triton X-100, Tween 20 and dimethyl sulphoxide. Inhibition profile indicated that crude protease contains, mainly, serine proteases. Enzyme preparation hydrolysed mainly casein and soy protein isolate.

4. The keratinolytic capacity of Bacillus sp. CL18 at moderate temperatures (30°C) might be appropriate for feather conversion, resulting in protein hydrolysates and proteolytic enzymes. Proteases are postulated to be added-value products that can be obtained from such a bioprocess.

KEYWORDS:

• Agro-industrial waste
• bioconversion
• enzyme
• feathers
• protease

Acknowledgements

This work was supported by Fundação de Amparo à Pesquisa do Rio Grande do Sul (FAPERGS) – Programa Pesquisador Gaúcho (Edital FAPERGS Nº 01/2013). T. J. Rieger and D. J. Daroit also thank the Programa Institucional de Iniciação Científica e Tecnológica – Conselho Nacional de Desenvolvimento Científico e Tecnológico (PIBIC/CNPq/UFFS).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Fundação de Amparo à Pesquisa do Rio Grande do Sul (FAPERGS) – Programa Pesquisador Gaúcho (Edital FAPERGS Nº 01/2013). T. J. Rieger and D. J. Daroit also thank the Programa Institucional de Iniciação Científica e Tecnológica – Conselho Nacional de Desenvolvimento Científico e Tecnológico (PIBIC/CNPq/UFFS).