Production of keratinolytic enzyme by a newly isolated feather-degrading Stenotrophomonas maltophilia that produces plant growth-promoting activity

Abstract

A novel feather-degrading Stenotrophomonas maltophilia R13 was isolated from rhizospheric soil of reed. The strain R13 produces keratinolytic enzyme using chicken feather as the sole carbon and nitrogen source. Addition of 0.1% glucose and 0.12% polypeptone to the feather medium increased the enzyme production. The optimum temperature and initial pH for the enzyme production were 30 °C and 7.0. The maximum yield of the enzyme was 82.3 ± 1.0 U/ml in the optimal feather medium; this value was about 5.5-fold higher than the yield in the basal feather medium. S. maltophilia R13 possessed disulfide reductase activity along with keratinolytic activity. As a result of feather degradation, 18 free amino acids were produced in the culture; the concentration of total amino acid was 2298.8 μM. The strain R13 produced IAA in the optimal feather medium without l-tryptophan supplementation, indicating simultaneous production of keratinolytic activity and IAA by S. maltophilia R13. The strain R13 grown in the optimal feather medium also inhibited mycelial growth of some phytopathogenic fungi. This result suggests that antifungal activity of the strain R13 could be produced in the same conditions observed for keratinolytic activity. Thus, S. maltophilia R13 could be not only used to enhance the nutritional value of feather meal but is also a potential bioinoculant in agricultural environments.