Recovery and characterization of structural extracellular biopolymers from aerobic granular sludge treating citrus industrial wastewater

Microbial polymer production has gained significant interest in recent years due to its potential for sustainable material recovery from renewable resources, such as wastewater, instead of using conventional petroleum-based polymers. Among these biopolymers, those extracted from aerobic granular sludge (AGS) have attracted increasing attention. AGS is an innovative wastewater treatment technology for both municipal and industrial effluents. Aerobic granules are dense, compact, and self-immobilized microbial aggregates capable of performing multiple biological treatment processes simultaneously (Campo et al., 2022). Bacteria in AGS are embedded in a complex extracellular polymeric substance (EPS) matrix, which provides structural stability and protection against external agents. Alginate-like exopolysaccharides (ALEs) are the primary components of EPS and are referred to as structural EPS (sEPS) due to their crucial role in maintaining the integrity of the granules (Felz et al., 2016). Bacterial-derived ALEs comprise a mixture of biopolymers, including polysaccharides, proteins, humic acids, and lipids. ALEs have garnered attention for their unique properties, including strong gelling ability, biocompatibility, and biodegradability, making them highly valuable for industrial applications. While the majority of literature studies on this topic focus on sEPS extracted from AGS for the treatment of municipal wastewater, limited research is available on sEPS extraction from AGS treating industrial effluents. This study aimed to evaluate the productivity and characteristics of ALEs extracted from AGS treating an industrial wastewater from a citrus industry.