Recovery of cyanophycin granule polypeptide from activated sludge: carbon source dependence and aggregation-induced luminescence characteristics

Highlights

● Sodium acetate significantly enriched the CGP synthetase-encoding gene.

● The highest CGP yield was obtained from activated sludge fed with sodium acetate.

● Biofilm is more conducive to CGP accumulation compared with floc sludge.

● Aggregation-induced luminescence of CGP was first reported.

Abstract

In the sewage treatment process, facilitating the conversion of pollutants into value-added resources holds great potential for reducing the amount of greenhouse gas emissions and promoting economic circulation. Cyanophycin granule polypeptide (CGP), a recently discovered high value-added biopolymer present in activated sludge, has provided new avenues for the recovery of resources. However, the mechanisms that regulate CGP synthesis and the characteristics of this biopolymer in activated sludge remain unclear thus far. This study investigated the synthesis of CGP, polyhydroxyalkanoates (PHA), and alginate-like exopolysaccharides (ALE) in various microbial aggregates under different carbon sources feeding conditions. Our results showed that the CGP yields was superior that of PHA and ALE when subjected to identical carbon source feeding conditions. Furthermore, biofilm was more conducive to CGP accumulation than floc sludge. Compared with glucose and methanol, sodium acetate significantly enriched the CGP synthetase-encoding gene (cphA_abundance = ~17419), resulting in the highest CGP yield (average 107.1 mg/g MLSS) in both biofilm and floc sludge. This study is the first to reported the characteristic fluorescence of CGP (Ex/Em = ~360/450 nm) caused by the aggregated luminescence of arginine on the side chains. Overall, this study highlights the potential application of CGP as a fluorescent material and offers insights into CGP recovery from activated sludge in wastewater treatment plants.

Graphical abstract

Keywords

Cyanophycin / Polyhydroxyalkanoate / Alginate-like exopolysaccharides / Bioresource recovery / Aggregation-induced luminescence

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. U22A20617), the Natural Science Foundation of Hunan Province, China (Nos. 2021JJ30664, 2022JJ30559, and 2022JJ50131), and Environmental Protection Research Project of Hunan Province, China (No. HBKT-2022036).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11783-024-1776-7 and is accessible for authorized users.

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