When feather-degrading Bacillus licheniformis is grown in culture, it secretes a keratinase that hydrolyzes the β-keratin matrix of a feather, thereby releasing oligopeptides that dissolve into the medium surrounding the feather and feather-degrading bacilli. These peptides absorb light passed through a sample of medium from which feather fragments, melanin granules, and bacteria have been removed by centrifugation. Samples of medium in which white, nonmelanic feathers are degrading absorb more light than samples of medium in which black, melanic feathers are degrading, which indicates that more oligopeptides are dissolved in medium surrounding white feathers than in medium surrounding black feathers. The differential absorption of light supports the conclusion that B. licheniformis degrades white feathers more rapidly than black feathers.