A Study Of The Industrial Keratin Product After Optimization Of Solid State Fermentation Process By Bacillus Licheniformis 1411-1 And Streptomyces Sp. B221

A large amount of wool or feather is produced as keratinous waste products at poultry processing plants with potential worldwide environmental impact. Keratin is a good source of feed protein, but it could not be degraded by ordinary protease such as pepsin or trypsin. Solid state fermentation (SSF) is a low energy-consuming and environment-friendly process. Now the solid-state fermentation technology is used more and more by people to solve the growing energy crisis and environmental issues. In this paper, we started from the Bacillus licheniformis NJU-1411-1 and Streptomyces sp. B221 which were isolated by our laboratory, and optimized the SSF process of the strains. We also optimized ingredients of the industrial seed culture medium to reduce production cost. In the stage of industrialization, we also studied amino acid content and digestibility of the product. The study laid a foundation for the using and degradation of keratinous resources by microbial technological ways. The following achievements were gained:(1) For both strains, to optimize the solid-state fermentation conditions, we investigated the influence of moisture level, initial pH, temperature and incubation time. The optimal fermentation conditions of moisture level, pH, temperature and incubation time were 15ml/10g wool keratin, pH 8 or 9,40℃ and 5 days respectively.(2) To reduce production cost, ingredients of the industrial seed culture medium were optimized. In the first stage we used starch、corn steep liquor and peptone to replace glucose、yeast extract and soy flour. In the second stage, we found that Bone peptone water (15% or 20%) also could be used as seed culture medium.(3) The amino acid contents of products and raw materials were determined by high performance liquid chromatography (HPLC). Soluble protein and water-soluble substances were also determined. We found that the amino acid content of products was lower than raw materials. But soluble protein is the main component of water-soluble substances, and both of them gradually increased with the development of the fermentation process.(4) The crude protein content, digestibility in vitro of products and raw materials were also determined. And we found that the crude protein content of keratin decreased from 86.84% to 83.97% after the SSF process, while the digestibility in vitro of keratin increased from 77.44% to 82.20%.(5) Also the digestibility of the fermentation product in pigs was studied and the result was found to be 85.43%.