Production of amino acids by mixed bacterial strains-mediated solid state fermentation of feathers and dynamic changes to the fermentation system

Abstract

Bioprocessing of chicken feather wastes for production of free amino acids was investigated by solid-state fermentation (SSF) with (1) single strain, (2) double strains, (3) triple strains of B. licheniformis TCCC 11593, B. alcalophilus TCCC 11004 and B. subtilis TCCC 11279. The maximum production of total amino acids amounting to 161.35 mg/g was obtained under optimal SSF conditions: feather concentrations 1.0 g/250 mL, moisture contents 1:9 (w/v), inocula ratios (v/v) of 5:5:3 for B. licheniformis: B. alcalophilus: B. subtilis respectively, 60 h fermentation. Monitoring of mixed bacterial populations in the SSF process by real-time PCR indicated that B. alcalophilus was the dominant microorganism present in the SSF cultures. Moreover, measurements of dynamic changes in multienzyme activities in the SSF process suggested that, in terms of amino acid production, keratinase might play an important role in the initial hydrolysis of keratin and the further hydrolysis was most likely to be accomplished by elastase, collagenase, alkaline protease, and neutral protease elaborated by the three mixed bacterial strains. The above results indicated that mixed-strain SSF could serve as a cost-effective method to utilize chicken feather wastes to produce value-added feed additives or organic fertilizers.