| Except only a few of feathers are used as textile materials and handicraft applications, most of them are treated as waste disposal. The main ingredients of the feathers are keratin, which can be decomposed into the peptide and amino acid, and then become the raw materials for agricultural, commodities or pharmaceutical industry. Traditional physical and chemical degradation methods will cause environment pollution, while the microbial degradation method is mild. It can not only avoid the environment pollution, but also can degrade feathers to be useful peptide amino acids. Keratinase are thought as the key factor for the biodegradation of macromolecular substances, thus researches about degradation of keratin are focused on the purification and physicochemical properties of keratinase and the construction of genetically engineered bacteria. However, keratinase is not the only key factor of microbial degradation of feathers, the biodegradation of feathers also requires other molecules. Studies about the keratinase and the construction of genetically engineered bacteria only can’t improve the efficiency of the feather degradation. So it is very important to study the mechanism about keratin degraded by bacteria.The related genes of bacterial degradation of keratin are stimulated by the external signal transferring into the bacterial cells. The feather powders are a kind of insoluble substrate, which can’t enter the cells directly and induce the expression of the keratin degradation related genes. According to the previous studies in our lab, we think that insoluble feathers are degraded into soluble fragments by the background expressed keratinase of the bacteria. Those fragments will bind to the bacterial cell membrane receptor, then some kind of signal is transferred into cells, then the degradation system is induced to open. In this paper, Stenotrophomonas maltophilia(S. maltophilia) DHHJ is induced to produce keratinase by keratin monomer. We focus on the research about the role of keratin monomer in this process.Keratin monomer was obtained successfully with chemical hydrolysis method. The keratin is about 10 kD. We used keratin and keratin fragments which were hydrolyzed by Proteinase K to induce S. maltophilia DHHJ to produce keratinase, no keratin as negative control, feathers as positive control. We measured the keratinase activities within 72 hours. When there was no inducement, the expression of the keratinase was low and the keratinase activity was lower than 0.5U/mL. S. maltophilia DHHJ could be induced to produce the keratinase by both keratin and the feathers. The highest keratinase activities were both measured in 48 h. The fragments could also induce S. maltophilia DHHJ to produce the keratinase, but the keratinase activities were much lower, which was 2.3U/mL highest. The result showed that keratin could induce the expression of related gene about the keratin degradation.The interaction between keratin and S. maltophilia DHHJ was further clarified through the fluorescence labeling technique, using fluorescence microscope and CLSM. S. maltophilia DHHJ was co-cultured with keratin labeled by FITC(FICT- Keratin), FITC-Keratin: BSA and FITC respectively for 3 hours. We measured the fluorescence value of both supernatant and sediment. The fluorescence value of FITC was stable both in supernatant and sediment, and the value in FITCKeratin and FICT-Keratin: BSA were rising. It meant that BSA and FITC-Keratin had a competitive relationship in combining to the binding site in the surface of S. maltophilia DHHJ. S. maltophilia DHHJ would choose to combine with BSA. After most of the BSA were used, S. maltophilia DHHJ would use FITC-Keratin instead. At that time, the signal pathway was opened and the keratin degradation related genes are induced to express. The results of this paper are meaningful for the further analysis of keratin degrading signaling pathway analytic foundation and also have a positive effect on the resource utilization of keratin. |
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