Extraction of flocculants from a strain of Bacillus thuringiensis and analysis of their properties

In a preliminary screening study,our laboratory isolated from the biofloc in aquaculture waters a strain of Bacillus thuringiensis,which produced highly efficient bio-flocculants.In the present study,we extracted the crude flocculants from this strain and analyzed their properties.Distribution analysis indicated that the flocculants were mainly distributed in the supernatant of the fermentation liquid.The flocculants were extracted using an ethanol extraction method,and the chemical compositions and morphology of the crude flocculants were analyzed using the Molish reaction,Fehling reaction,ninhydrin reaction,biuret reaction,phenol-sulfuric acid assay,Coomassie brilliant blue staining,ultraviolet scanning,infrared scanning and scanning electron microscopy.The carbohydrate composition of the polysaccharides in the flocculants was analyzed with thin layer chromatography.The results indicated that flocculants were solid substances with an ivory white color and their texture was loose and soft.Visualization under scanning electron microscopy revealed that their ultra-morphology consisted of small,long and fiber-like shapes.Chemical and physical analyses indicated that polysaccharides accounted for 34.5%of the components in the crude flocculants.The monosaccharides present in crude flocculants included mainly glucose,galactose and mannitose.

Bacillus amyloliquefaciens (IAE635) and their metabolites could purify pollutants, Vibrio spp. and coliformbacteria in coastal aquaculture wastewater

High-density aquaculture often causes the emission of polluted water to the marine environment in the coastal areas of China.To solve the aquaculture-related water quality problems,it is appropriate to adapt eco-friendly methods,such as using microbes and their metabolic products to purify polluted water.In this study,the purifying effects ofBacillus amyloliquefaciens(IAE635)metabolites(poly-γ-glutamic acid;PP)and IAE635 combined with their metabolites(MP)on turbidity,COD,NO3--N,NH4+-N,Vibrio spp.andcoliform bacteria in coastal aquaculture wastewater were conducted in the lab and in situ ponds.The results showed that the removal ofturbidity,COD,NH4+-Nand NO3--Nwith PP and MP was more significant(p<0.05).Compared to Control treatment(Co),the turbidity,COD,NH4+-Nand NO3--N concentrations at 24thhour were evidently reduced by 86.6%,87.5%,83.3%and 58.0%for PP,87.9%,93.5%,86.5%and 78.0%for MP,respectively.The populations of water pathogens under PP and MP were also significantly(p<0.05)removed compared with those of Co;at 24thhour,the Vibriospp.and coliform bacteria were decreased by 68.7%and 66.3%forPP,75.0%and 67.1%for MP,respectively.The water purifying effect of MP was slightly better than that of PP.In situ pond purification test demonstrated that MP significantly lowered the concentrations of turbidity,COD,NH4+-N,NO3--N and NO2--N,which was more effective than EM.A significantly higher(p<0.05)γ-PGA concentration and the total bacterial population for MP compared to PP indicatedthatMPpurifies the coastal aquaculture wastewaterby both flocculation and microbial decomposition.The application of MP will benefit the aquaculture industry by providing a novel method for the removal of chemical pollutants and pathogens.