Bioresources Inner-recycling Between Bioflocculation Of Microcystis Aeruginosa And Its Reutilization As A Substrate For Bioflocculant Production

The efficient and low energy recovery of algae has been an important topic in water treatment.Because of its non-toxic / natural degradation and high flocculation efficiency,bioflocculant has received extensive attention in water treatment and biological fermentation projects such as algae removal and recovery.However,most studies are still at the laboratory level and basic research stage,the main reasons include: firstly,the composition of bio flocculant by flocculating strains vary greatly,so the need for specific screening of bio flocculant in different water containing algae;secondly,flocculant producing strains to produce a lot of preparation in the engineering application of bioflocculant algae containing wastewater treatment and recycling of the algae,but due to mass production cost of medium flocculant producing bacteria limit flocculant.Based on the above reasons,we developed a method for algae biomass resources within the wastewater cycle,with Microcystis aeruginosa as the research object specific screening can produce bioflocculant flocculation of the algae,algae and waste recycling as the main flocculation culture medium,culturing the strain to produce more flocculant can used for recycling and algae water treatment flocculant.First,the bioflocculant-producing strain was isolated from an activated sludge of a secondary wastewater treatment plant in Changchun,China.The 16 S rDNA sequence of the strain was 99.9% similar to Citrobacter sp.and K.pneumoniae.With Citrobacter sp.as the main research object,flocculated algae biomass were reutilized as the flocculant producing medium with different supplementary components,including organic carbon source,organic nitrogen sources,inorganic nitrogen sources etc.We examined the bioflocculant production efficiency,flocculation efficiency for M.aeruginosa and determined the optimal bioflocculant conditions.Design Expert Software(version 8.0)was used for the statistical design of experiments and for the data analysis.Central composite design(CCD)and response surface methodology(RSM)were used to optimise the different factors impact on the algae flocculation efficiency,inlcuding: temperature,pH,flocculation,time,bioflocculant dosage and Ca2+ cationic inducer concentration.The experimental results showed that 3.4±0.1 g of bioflocculant was produced by 10 g/L of wet biomass of M.aeruginosa(high-pressure steam sterilized)with an additional 10 g/L ofglucose as an extra carbon source.Second,the microbial bioflocculant of Citrobacter sp.AzoR-1,termed MBF-12,was characterized by Fluorescence excitation emission matrix(EEM),Molecular weight and Fourier-transform infrared spectrum(FTIR).The EEM spectrum shows the composition of bioflocculant from algae biomass culture include polysaccharide(Ex/Em =300-450/350-400 nm),polyaromatic-type polysaccharides(Ex/Em = 250-300/400-550 nm),and tyrosine/tryptophan amino acids(Ex/Em = 200-250/300-400 nm).MBF-12 is a long-chain biopolymer which molecular weight was 270 kDa,so it is long enough to perform bridging between M.aeruginosa cells.The Fourier-transform infrared(FTIR)spectrum of purified MBF-12,which was generated from algae biomass culture,exhibited a broad hydroxyl stretching peak at 3423 cm-1 and an amine band at 1630-1550 cm-1.The adsorption peak at 2930 cm-1indicated the C-H stretching vibration.Strong absorption peaks present in the range of 1100-1200 cm-1are typical peaks for proteoglycans.The study zeta potential of bioflocculant MBF-12 was mainly negatively charged.The main bioflocculation mechanisms of bioflocculant for microalgae recovery is interparticle bridging and biodsorption.Third,the metabolic and gene expression profiles of the microorganisms during the microalgal consumption were identified through transcription analyses,to reveal the pathways underlying the bioflocculant production.Genes related to these bioflocculant biosynthesis pathways were classified into different functional categories using the Kyoto Encyclopedia of Genes and Genomes(KEGG)Automatic Annotation Server(KAAS)program.According to Transcriptome data analysis,including the polyketide sugar unit,lipopolysaccharide,peptidoglycan,and terpenoid backbone.Bioresources inner-recycling,between bioflocculation of Microcystis aeruginosa and its reutilization as a substrate for bioflocculant production,was achieved in this work.By this means,the bioflocculation of Microcystis aeruginosa reached as much as 95%,with the bioflocculant produced from Citrobacter sp.AzoR-1 by the harvested Microcystis aeruginosa biomass.Our work provides a noval way for the sustainable treatment and resource utilization of algae containing water.This study from two aspects of large-scale application of algae water resource processing and bioflocculant of established recycling waste for the cultivation of algae flocculant producing bacteria,and will be further used for bio flocculant recycling and waste water with algae algae,the establishment of a reliable and efficient raw material resources within the circulatory system.At the same time,the mechanism of flocculation and flocculation mechanism of algal cells in two aspects of flocculant producing bacteriafrom chemical and transcriptome,lay a solid theoretical basis for the comprehensive analysis of the effective components of flocculant and regulation of flocculant producing bacteria flocculating metabolic pathway.It provides the strategy for the industrial production and application of bioflocculant,and plays an important guiding role in improving the production of bioflocculant,reducing the production cost of flocculant,and controlling the industrial production of bioflocculant.At the same time,it provides a new idea for the sustainable treatment and resource utilization of algae bearing water.