A novel Pseudomonas sp. strain with high flocculation efficiency for aquaculture wastewater treatment.

A bacterium showing excellent flocculation performance was isolated from sludge. Through 16S rDNA sequencing, morphological observation, and enzyme characterization, the strain was found to represent a novel bacterium of the Pseudomonas sp., termed Pseudomonas sp. GXUN74702. Pseudomonas sp. GXUN74702 was isolated from the sludge of Siyuan Lake in Guangxi Minzu University. Research showed that strain GXUN74702 had good flocculation performance. After the strain was cultured in fermentation medium (pH 7.0) containing glucose as carbon and urea as nitrogen, shaking at 30 °C 180 rpm for 36 h, the flocculation rate reached 92.5% when treating kaolin suspension with 2 mL of the fermentation broth. The microbial flocculants (MBF) GXUN74702 contained 78.90% total sugars and 6.78% protein. Ion chromatography detection showed that the monosaccharide constituents of MBF-GXUN74702 were most mannose (10.55 µg/mg), glucose (5.34 µg/mg), and glucosamine hydrochloride (1.48 µg/mg). The use of MBF-GXUN74702 for treating aquaculture wastewater was then explored, demonstrating chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal rates of 52% and 20%, respectively. In summary, Pseudomonas sp. GXUN74702 is a newly identified Pseudomonas sp. strain that shows highly efficient flocculation performance in treating aquaculture wastewater, suggesting its potential value in wastewater treatment applications. The fermentation medium components of Pseudomonas sp. GXUN74702 identified in this study are simple and easy to obtain, and the fermentation conditions of the strain are mild and not harsh, so a large number of fermentation liquid with high flocculation performance can be obtained in a short time. The main component of MBF-GXUN74702 has been proved to be polysaccharides that are superior to inorganic and synthetic organic flocculants owing to their non-toxicity, biodegradability, high efficiency, free secondary pollution, and wide adaption to pH variation. At present, the team has obtained the flocculants powder of the strain under laboratory conditions. The production process of this powder is simple, the yield and flocculation rate are high, and the property is stable and easy to preserve.