以羊毛粉为唯一碳氮源,对苏云金芽孢杆菌菌株NJY1的液体发酵产角蛋白降解酶的工艺条件进行了优化,确定最佳发酵培养基为:羊毛粉15.0 g/L,MgSO4.7H2O0.3 g/L,NaCl 0.3 g/L,CaCl20.02 g/L,K2HPO40.72 g/L,KH2PO40.36 g/L;最佳发酵条件:初始pH值7.5～8.0,接种量2.0%,菌龄12 h,发酵温度37℃。测定表明,优化后的培养条件下发酵36 h,角蛋白酶活力达到最高,为88.77 U/mL,比未优化前酶活力增加247.91%。
A strain of degrading feather keratin bacterium with high efficiency was isolated from environment by adopting the culture medium taking feather meal as sole carbon and nitrogen source.This strain was identified as Bacillus pumilus by morphology,physiological and biochemical experiments and 16SrDNA gene analysis,and named as the Bacillus pumilus WHK4.The degradation rate of feather keratin reached to 85.76% after 48h fermentation.The results indicated that WHK4 was an appropriate strain for exploring microorganic fermentation system to degrade feather keratin,and had a great potential to be applied in producing high quality protein feed.
To obtain high efficient degradation bacteria of hemoglobin,strain NJM4 from slaughterhouse sewer in Nanjing was isolated by blood agar plate.The ability of degeneration hemoglobin was assessed by hematolysis circle ratio.Initially,the strain was identified as Bacillus pumilus based on morphology observation,physicochemical characteristics and 16S rRNA sequence analysis(GenBank ID:EU234500).The results showed that the hemoglobin could be degraded into small molecular multi-peptides,and after 24 h incubation under 37 ℃,120 r/min,the degradation rate of hemoglobin could reach to 53.64%.
To obtain high efficient keratin-degraded bacteria,strain NJY1 from environment soil was isolated by feather meal as its sole source of carbon,nitrogen. Strain NJY1 was identified as Bacillus thuringiensis based on morphology observation,physicochemical characteristics and 16S rRNA sequence analysis(GenBank ID:EU624205) due to100% homology with it. The degradation rate of feather was up to 72.5% after 72 h of fermentation at 37℃,and soluble protein concentration in fermented liquid was 25.2 mg/ml. We provided a high efficient keratin-degraded bacterium to product high quality protein feed.
