Keratinases and sulfide from Bacillus subtilis SLC to recycle feather waste.
The aim of this study is to investigate the culture conditions of chicken feather degradation and keratinolytic enzyme production by the recently isolated Bacillus subtilis SLC and to evaluate the potential of the SLC strain to recycle feather waste discarded by the poultry industry. The SLC strain was isolated from the agroindustrial waste of a poultry farm in Brazil and was confirmed to belong to Bacillus subtilis by rDNA gene analysis. There was high keratinase production when the medium was at pH 8 (280 U ml(-1)). Activity was higher using the inoculum propagated for 72 h on 1% whole feathers supplemented with 0.1% yeast extract. In the enzymatic extract, the keratinases were active in the pH range from 2.0 to 12.0 with a maximum activity at pH 10.0 and temperature 60°C. For gelatinase the best pH was 5.0 and the best temperature was 37°C. All keratinases are serine peptidases. The crude enzymatic extract degraded keratin, gelatin, casein, and hemoglobin. Scanning electron microscopy showed Bacillus cells adhered onto feather surfaces after 98 h of culture and degraded feather filaments were observed. MALDI-TOF mass spectrometric analysis showed multiple peaks from 522 to 892 m/z indicating feather degradation. The presence of sulfide was detected on extracellular medium probably participating in the breakdown of sulfide bridges of the feather keratin. External addition of sulfide increased feather degradation.
Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes (IMPG), Bloco I, Centro de Ciências da Saúde (CCS), Universidade Federal do Rio de Janeiro (UFRJ), Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21941-590, Brazil.
Sabrina Martins Lage
SM
Cedrola
Ana Cristina Nogueira
AC
de Melo
Ana Maria
AM
Mazotto
Ulysses
U
Lins
Russolina Benedeta
RB
Zingali
Alexandre Soares
AS
Rosado
Raquel S
RS
Peixoto
Alane Beatriz
AB
Vermelho
D000818:Animals; D001412:Bacillus subtilis / Q000737:chemistry* / Q000145:classification / Q000201:enzymology* / Q000302:isolation & purification; D001422:Bacterial Adhesion; D001938:Brazil; D002645:Chickens; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D005241:Feathers / Q000378:metabolism* / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D017744:Medical Waste Disposal / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013440:Sulfides / Q000302:isolation & purification / Q000378:metabolism*; D013696:Temperature
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D017744:Medical Waste Disposal; D012336:RNA, Ribosomal, 16S; D013440:Sulfides; D010447:Peptide Hydrolases; C035855:keratinase