Improvement of actinorhodin production yield in Streptomyces coelicolor by immobilized-cell cultivations by using PCL- and PLA-based films

Actinomycetes are Gram-positive bacteria producing most of naturally occurring antibiotics (Donadio et al., 2010). At industrial level, antibiotics are produced by submerged fermentations where the actinomycete filamentous morphology negatively affects bioproductivity (van Dissel et al., 2014). Microporous membranes for bacterial cell-immobilization were already proven increasing bioproductivity in Streptomyces coelicolor, that is a model actinomycete producing the blue pigmented actinorhodin (ACT) antibiotic (Scaffaro et al., 2016). To develop an immobilized-cell bioreactor system, different kinds of polycaprolactone (PCL) and polylactic acid (PLA) films were produced by an electrospinning-based approach. S. coelicolor cells immobilized on PCL and PLA membranes formed a dense biofilm as observed by scanning electron microscope. An increased biomass content and more than 4-fold ACT yield was obtained in comparison with free-cell cultivations for all the membranes, with O2-plasma treated PLA membranes as the most effective. Therefore, the membranes are suitable for bioproduction improvement in actinomycete-based fermentation and encourage studies for process scaling-up.