| For a long time, people have always thought that the bacteria survival based on the planktonic. Until the past decade, because the birth of Laser Scanning Confocal Microscope, it was discovered that, the main way of life for the most bacteria is biofilm, and supplemented by planktonic. Boifilm can be formationed by pure strains, and can also be composed of multi-strain. The bacteria of biofilm is different from the planktonic bacteria, they have enhanced resistance to antimicrobial agents such as antibiotics, harsh environment and host immune defense mechanism. The bacteria of biofilm have special characteristic on physiology, metabolism, the degradation or use of substrate, and resistance to the environment. Therefore, people attaches great importance to the research of biofilm.At present, the study on biofilm is mainly in the medical field, there are more relatively study of pathogenic bacteria biofilm, but for the probiotics such as lactic acid bacteria, there is very little research. Owing to their stable and easy of operation, various biofilm processes have already been implemented in industry with great success over the last few decades. In addition, biofilm reactors for productive catalysis have the potential for continuous operation based on low-cost self-imm-obilization of viable, robust and self-regenerating cells.As one of the most important probiotic of human body, lactic acid bacteria has been widely used in dairy fermentation industry. In this study, the research object is Streptococcus thermophilus and Lactobacillus bulgaricus, we made they formed mixed biofilm on the appropriate carrier surface, carried out a preliminary exploration for the resistance and inoculated in a continuous process of the mixed biofilm. The contents and results are as follows:1. Screening for carrier of lactic acid bacteria biofilmIn this part, the research object is the single biofilm of Streptococcus thermophil-us and Lactobacillus bulgaricus, we made the biofilms formed on different carrier surface, then selected stainless steel mesh and coconut as suitable carrier materials for lactic acid bacteria biofilm formation by comparing. And then made the mixed biofilm of Streptococcus thermophilus and Lactobacillus bulgaricus on the two carrier materials as study object, carried out colony count for the biofilm and observed it, the result showed that, the cfu(colony-forming units) of the mixed biofilm maintained stable for seven consecutive days, and it had typical biofilm structure, and it also showed that the method of the lactic acid bacteria biofilm formation in this part is feasible.2. Preliminary study for resistance of lactic acid bacteria biofilmIn this part, the study object is the mixed biofilm of Streptococcus thermophilus and Lactobacillus bulgaricus on the stainless steel mesh and coconut, research for the resistance of it, preliminary proved that the mixed biofilm formed on the two carriers showed stronger resistance than planktonic in the environment of50℃ã€60℃and pH2.0, this confirmed that the lactic acid bacteria biofilm of this research had tolerance for adverse environment in certain areas, and it also proved that the lactic acid bacteria biofilm formed by the method in this research was the typical biofilm.3. Preliminary study for continuous inoculation process of lactic acid bacteria biofilmIn this part, the research object is the mixed biofilm of Streptococcus thermophi-lus and Lactobacillus bulgaricus on the stainless steel mesh, operate the experiments about fermentation and continuous inoculation process of lactic acid bacteria biofilm, we found that, the means of use the lactic acid bacteria detached from biofilm instead of normal inoculation is possible; the study also showed that the lactic acid bacteria mixed biofilm could provide cfu at least106/ml continuously and stably, and if we use some simple conditions for the resumption(such as "feed film" process), the process will last for fifteen cycles or more, and keep up the good stability. |
