Engineering aerobic granular sludge for enhanced curdlan biosynthesis: the impact of organic loading rate, carbon-to‑nitrogen ratio, and feeding strategy

This study reports, for the first time, the recovery of curdlan from aerobic granular sludge (AGS) wastewater systems. Nine bench-scale experiments were conducted to evaluate the effects of organic loading rate (OLR), carbon-to‑nitrogen ratio (C/N), and feeding strategy on curdlan biosynthesis during wastewater treatment. At OLR = 2.1 kg COD/m 3 ∙d with C/ N = 10 and 30 min feeding/30 min stationary phase, curdlan yield reached 74 ± 6 mg/g biomass, while at OLR = 2.1 kg COD/m 3 ∙d with C/ N = 30 and 10 min feeding/50 min stationary phase, curdlan yield was 69 ± 11 mg/g biomass. Univariate statistical analysis showed that there was a statistically significant association between curdlan production and OLR, and between curdlan production and feeding strategy at α = 0.05. Although synthetic wastewater was used for controlled bench-scale experiments, the complex composition of municipal wastewater may further affect microbial dynamics and curdlan biosynthesis. These findings highlight AGS as a promising platform for integrating curdlan recovery into wastewater biorefinery. • Curdlan was recovered from AGS systems: 69 ± 11 mg/g and 74 ± 6 mg/g peak yields. • OLR and feeding strategy significantly influenced curdlan production (α = 0.05). • Optimal conditions: OLR = 2.1 kg COD/m 3 ∙d, C/ N = 10, & 0.5 h feeding/0.5 h resting. • Curdlan recovered was identified by aniline blue staining, FT-IR, and NMR. • Curdlan recovery from AGS shows promise for wastewater biorefinery applications.