Screening Of Superior Bioflocculant-producing Ultraviolet Mutagenesis Strain Kebsiella Sp.NIII2and The Study On Its Specificity

Bioflocculant is a kind of metabolites produced by microorganisms，which isbiodegradable, can be safe and efficient, nontoxic and no secondary pollution of watertreatment agent. However，the microbial flocculant has not been widely used in result ofits large yield and high cost. So screening highly effective bioflocculant producingbacterium，improving the flocculation activity and its yield，reducing production cost，has practical significance to realize the mass industrial production and application ofmicrobial flocculants.Based on much abundant research of this project group， this experimentmutagenesis strain by UV from a bioflocculant producing bacterium Kebsiella. On thebasis of producing flocculant mutantstrains，the culture medium and fermentationconditions of bioflocculant producing by the mutantstrain were optimized and thesecretion of growth characteristics of flocculants was studied. The main researchconclusion is as follows：(1) A genetic stable and high yield bioflocculant mutantstrain NIII2has beenobtained by UV induced mutation from Kebsiella sp.NIII2.(2) Factors which effect the mutantstrain NIII2-I producing flocculant，influencesize order is pH> phosphate＞quantity of Mg＞inoculation amount. Mutation strainNIII2–I best culture medium was as follows：sugar20g/L, sodium nitrate2.4g/L,MgSO4solution16.8mg/L (with Mg2+), phosphate buffer27g/L(with PO43-), originalculture medium pH value of8, culture temperature30℃, the night growing seeds2ml,culture fermentation time of72h. The flocculant produced by mutation bacteria NIII2-Iwhich yield reached up to12.11g/L. (3) Microbial flocculant produced by wild strain NIII2and mutagenesis NIII2-I hasalmost the same functional group.They have characteristic absorption peak of proteinand sugar，which contained-OH，-COOH，-NH，C-O-C.(4) Culture temperature and nitrogen source effect the content of total sugar andprotein of microbial flocculants. When the content of protein in the microbial flocculantis higher，the flocculation effect is better. Compared with the wild fungus, proteincontent in flocculant produced by mutant strain NIII2-I is higher.(5) Microbial flocculant produced by Wild fungus NIII2and mutagenesis NIII2–Ihave different particle size distribution. Particle size distribution of the flocculant fromthe wild fungus NIII2is in0.4-3.0um and3.0-100um range, and it hasthe largerproportion of flocculant in0.4-3.0um range. Particle size distribution of the flocculantfrom mutantstrain distribute in0.4-2.5um and3.5-60um range. From the statisticalresults，within the scope of0.4-2.5um flocculant proportion is larger.3.5-60um rangeof flocculant molecular size is divided into three range which are4-10um,10-28um,28-60um，and the proportion is increasing gradually. It can be seen obviously that themolecular weight distribution of flocculant produced by mutant strain is more scattered.The result of the study above layed a foundation for industrial production andapplication of microbial flocculants produced by strain NIII2and mutant strain.