Isolation And Identification Of Floc-producing Bacteria And Flocculation Component Analysis

Bioflocculants are polymers produced by microorganisms during their growth, and their obvious advantages are non-poisonous, readily biodegradable and without pollution to the environment. With the enhancement of people's environmental consciousness, the studies of bioflocculants are gaining more and more attentions.In this paper, 4 strains bacteria were obtained respectively from activated sludge and biofilm at low temperature by primary screening and secondary screening, they performed flocculating properties effectively and were named DG2, DN1, H8, and H13. The flocculating rates with kaolin cay were DG2 87.35%, DN1 81.33%, H8 85.79%, H13 78.44%. Further study on these flocculant-producing bacteria indicated that the strain H8 sendimented kaolin cay most effectively and with rapid speed from 10℃to 20℃. It was identified as Pseudomonas sp. based on its morphological and physiological characteristics and 16SrRNA sequencing method. This is the frist time to report about bioflocculants produced by Pseudomonas sp.at low temperature.In order to improve the flocculating activity of strain H8, the culturing conditions and flocculating conditions were optimized. The results showed that the optimal culturing conditions were: carbon source is glucoses, nitrogen source are yeast extract and peptone, medium initial pH8.0, culture temperature 10℃and culture time 20h; The best flocculating condition were: pH 9.0, adding amount of culturing liquid is 2%, sendimental time is 5 mins, the additions of CaCl2 were able to increase the flocculating rate and the optimal amount was proved to be 0.04%.The distribution of flocculants produced by strain H8 were tested, and the results showed that the effective flocculants were evenly distributed in supernatant and pellet, and extract flocculant. The supersonic method was eventually used to extract the bio-flocculants from the culturing liquid of strain H8, the optimal extracting condition were: F(frquency)=40Hz, T(time)=10min,R(rotational speed)=4000r/min. The ethanol was used to precipitate the flocculant and totally the extracting amount was about 0.562g/L. The components of bio-flocculants were detected through qualitative analysis and quantitive analysis. The results showed that the major components were polysaccharide and protein, with as much as 51% and 2.64 %, also there were amino sugar 0.38 % and glucuronide 1.3 %.