Applied microbiology and biotechnology uncovering the biosynthetic pathway of polysaccharide-based microbial flocculant

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ENVIRONMENTAL BIOTECHNOLOGY

Applied microbiology and biotechnology uncovering the biosynthetic pathway of polysaccharide-based microbial flocculant in Agrobacterium tumefaciens F2 Shanshan Pi 1 & Jiguo Qiu 2 & Ang Li 1

&

Liang Feng 1 & Dan Wu 1 & He-ping Zhao 3 & Fang Ma 1

Received: 6 March 2020 / Revised: 11 August 2020 / Accepted: 17 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract The low yield as bottleneck problem limits the application of microbial flocculant in water treatment. However, genetic information of microbial flocculant-producing strains can guide the regulation of microbial flocculant production, but it remains unknown. Agrobacterium tumefaciens F2 produced polysaccharide-based microbial flocculants in the fermentation medium but none in Luria Bertani medium; hence, the transcriptome was used to analyze the potentially associated genes with the production of microbial flocculants. Glucose, mannose, rhamnose, and galactose are the main sugar monomers, and genes (manA, glmM, manC, rfb genes, exo genes, etc.) with changed expression levels related to sugar monomers metabolism potentially participated in the biosynthesis of polysaccharide-based microbial flocculants. exoC, exoP, and manC were confirmed to participate in the biosynthesis via constructing the mutants F2-dexoC, F2-dexoP, and F2-dmanC. An exoF2 gene cluster was annotated due to the high percentage of matches between the genome sequences of strains F2 and C58, and exo genes in their genome sequences showed the similarity of 86~92%. The hypothetical pathway for the biosynthesis of polysaccharide-based microbial flocculants in strain F2 was proposed, laying the basis for the production yield regulation. Key points • An exoF2 gene cluster in the polysaccharide biosynthesis was annotated. • exoC, exoP, and manC genes participated in the polysaccharide biosynthesis. • A hypothetical biosynthesis pathway of polysaccharide in flocculant was proposed. Keywords Agrobacterium tumefaciens F2 . Polysaccharides . Microbial flocculants . Transcriptome . Biosynthetic pathway . exo genes Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00253-020-10850-2) contains supplementary material, which is available to authorized users. * Ang Li [email protected]; [email protected] * Fang Ma [email protected] 1

State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People’s Republic of China

2

Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, People’s Republic of China

3

College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, People’s Republic of China

Introduction Natural microbial flocculants are attractive due to their ubiquitous and environment friendly nature, biodegradability, and high application value (Salehizadeh et al. 2018; Yang et al. 2016). In gen