Facile and green synthesis of reduced graphene oxide/loofah sponge for Streptomyces albulus immobilization and ε-poly-l-lysine production

Facile and green fabrication of reduced graphene oxide on loofah sponge (rGOLS) carrier was applied for cell immobilization of ε-Poly-l-lysine (ε-PL) production. Due to surface properties including large specific surface area, high polarity, and low interaction energy, rGOLS-1 was employed as the optimum rGOLS to enhance immobilization of Streptomyces albulus. Compared with raw LS, batch experiments showed rGOLS-1 facilitated superior cell vitality for ε-PL production due to the presence of reduced graphene oxide. In the sequential fed-batch cultivation of Streptomyces albulus using rGOLS-1 with an aerobic plant fibrous-bed bioreactor (rGOLS-1-AFPB), the maximum ε-PL concentration and productivity reached to 39.2 ± 0.63 g/L and 0.48 g/L/h. The cells immobilized in rGOLS-1 with high vitality and ε-PL production efficiency were reused six times over a period of 624 h. This research afforded an effective approach to enhance the fermentation performance of immobilized cells with the design of an advanced immobilization carrier.