Enhancing erythromycin production by Saccharopolyspora erythraea E3::sucBA in chemically defined medium

Erythromycin, a clinically vital macrolide antibiotic biosynthesized bySaccharopolyspora erythraea, is predominantly produced using complex media derived from agricultural by-products. However, these complex media bring about batch-to-batch variation, complicate downstream purification, and increase the biological oxygen demand (BOD) of wastewater, thereby raising treatment costs and environmental footprints.To address limitations of complex media, this study focused on optimizing erythromycin fermentation by S. erythraea E3::sucBA in a chemically defined medium (CDM). The engineered strain E3::sucBA exhibits enhanced erythromycin synthesis capacity but suffers from a distinct early-stage growth retardation. Through targeted metabolomes analysis, insufficient intracellular glutamate was pinpointed as the key driver of this growth limitation and a tailored approach medium optimization approach was applied. Supplementing 0.5 g/L glutamate to CDM alleviated the lag, accelerating nutrient consumption and raising erythromycin from 930.1 mg/L to 1307.9 mg/L. Furthermore, a dynamic fed-batch concentration scaling fermentation strategy was developed in 5 L bioreactors, and an erythromycin titer of 4065.8 mg/L was achieved with higher cell density. Vitamin and cofactor addition further optimized productivity, resulting in a record 4847.4 mg/L erythromycin in CDM. In conclusion, this study provided an optimization framework for erythromycin fermentation in the CDM, and offered references for medium customization and fermentation process development in actinomyces antibiotic production, promoting green and efficient industrial manufacturing.