Research On Culture Optimization Of A Bioflocculant-producing Bacterium And Bioactive Flora Compounding

Flocculant plays a necessary part in wastewater treatment. Since traditional flocculants may damage ecological environment and harm human health, a type of "green flocculants", microbial flocculants, are greatly needed. Presently microbial flocculant-producing bacteria are mainly from soil, active sludge in sewage plant which have some limitations on marine pollution. In order to control marine pollution targeted, finding a high active microbioal flocculant has very important theoretical value and market prospect. By the way, the scope of application of microbioal flocculants have been expanded.Ruditapes philippinarum, known as mottled clam, has an abundance in China coastal areas. Its adhesion sludge showed excellent flocculation and decolorization activities. Researches revealed that the activities have a relationship with some flocculant-producing microorganisms residing in the adhesion sludge. In this research,11 strains have been isolated from the the adhesive sludge through sample collection, purification and high-efficiency screening.Subsequently, a high-efficiency flocculant-producing bacterium ZHT3-9 was selected out. By bacterial morphological observation, physiological and biochemical feature analysis, 16s rRNA whole gene sequencing and blast in Genebank, the strain ZHT3-9 was determined to be a speices of the genus Arthrobacter.The culture conditions and their effects on flocculation rate were studied. In terms of flocculation performance, the fermentation liquor of strain ZHT3-9 flocculated Kaolin suspension best with starch as carbon source, urea and ammonium sulfate as Nitrogen sources, C/N of 30/1, inoculation amount of 1.5mL, initial pH of 6 and 4-day cultivation.The crude flocculant MBF3-9 was prepared. By sugar and protein chromogenic reactions as well as UV scanning, the active substance in MBF3-9 was mainly polysaccharides, probably containing small amounts of protein, without nucleic acids.Four strains of flocculant-producing bacteria including strain ZHT3-9 were choosed to complexly cultured by two or three in a group. As a result, a group of high-efficiency compound strains was obtained. Its flocculating activity for kaolin clay was up to 90.2%. Measured by phenol sulfuric acid method, the percentage of polysaccharide was determined to be 58%.The COD removal rate for municipal wastewater was 71.17% when treated with the compound bioflocculants.