Analysis Of Contamination In Solid-State Fermentation Of Bacillus Subtilis And Investigation Of Adaptability To Low Nutrition

Bacillus is a probiotics to regulate water quality in aquaculture because of whose ability for degrading the organic matter quickly. The studies of Bacillus focusing on suppressing pathogenic bacteria, improving enzyme activation, the liquid fermentation and the solid state fermentation technology in laboratory condition. But few study about scaling up fermentation technology and mechanism in low-nutrient conduction. A strain FY99-01 was employed in this study. The aim of this study was to investigate the problem of infection occurred in biological in industry fermentation and the effect of different nutrient concentration on growth of Bacillus subtilis, which can scientific provide rules and clues for large-scale application aquiculture.The problem of contaminated were studied by spread plate method. The result indicated this problem was unavoidable during the solid state fermentation of B. subtilis because of the produce method and conduction. At the beginning of fermentation, contamination bacterial began to grow. After 20-hours culture, the cells of contamination bacterial increased. And this problem related the weather as well. Moisture would aggravate contaminated situation.The study on the growth of FY99-01 in low-nutrition condition showed when concentration of vegetative cells reached 108 CFU/ml, FY99-01 could maintain survival at least 24h in less than 50 times diluted peptone-beef extract liquid medium, however the cells of FY reduced 90-99% in more than 50 times diluted peptone-beef liquid medium after 24h. Similar results were obtained when adding inorganic salts. And it proves that lack of inorganic salts is main factor which limits growth of bacteria in low nutrition condition. When spore were put in 50 and 100 times peptone-beef extract liquid medium, some spore germinated but some of them changed their shape after budding. The 5- day test of CODMn of the medium, the results show on distinct difference between experiment group and control group, which reflects low metabolism level of microorganism.