Effect of PCL/PEG‐Based Membranes on Actinorhodin Production in Streptomyces coelicolor Cultivations

Abstract

The actinomycetes, Gram-positive filamentous bacteria, are the most prolific source of natural occurring antibiotics. At an industrial level, antibiotics from actinomycete strains are produced by means of submerged fermentations, where one of the major factors negatively affecting bioproductivity is the pellet-shaped biomass growth. The immobilization of microorganisms on properly chosen supports prevents cell-cell aggregation resulting in improving the biosynthetic capability. Thus, novel porous biopolymer-based devices are developed by combining melt mixing and particulate leaching. In particular, polycaprolactone (PCL), polyethylene glycol (PEG), and sodium chloride (NaCl) with different grain sizes are used to prepare PCL/PEG/NaCl blends in the melt. These blends are then leached to obtain PCL-based porous membranes that are used as solid support for the growth of Streptomyces coelicolor, a model streptomycete used to produce various antibiotics including the blue colored actinorhodin (ACT). Thereafter, the effect of the devices' characteristics on the bacterial growth and on the production ACT is evaluated. The results showed that ACT production is strongly dependent on the pore size distribution of the device. Moreover, membranes with pores ranging from 90 to 110 μm are able to offer a potential improvement in volumetric productivity of ACT if compared to conventional submerged liquid culture.

Secondary Metabolite Production from Industrially Relevant Bacteria is Enhanced by Organic Nanofibers

“…The density of the fibrous materials, related to the interconnected porosity of polymer nanofibers, which can reach values as high as 80–90%, also plays an important role, because it disfavors mycelia entanglements and formation of bacterial pellets, which cause suboptimal growth and production yields in SmF cultures (i.e., without solid substrates for cell adsorption) . In our samples, voids among fibers typically range around a few tens of μm, which well‐matches the size of pores (50–100 μm) requested for enhancing productivity . These findings indicate that cultivation systems supported by organic fibers allow the biosynthetic potential of filamentous microorganisms to be stimulated in vitro, opening a new field of application for electrospun polymers.…”

“…[34][35][36] In our samples, voids among fibers typically range around a few tens of μm, which well-matches the size of pores (50-100 μm) requested for enhancing productivity. [36] These findings indicate that cultivation systems supported by organic fibers allow the biosynthetic potential of filamentous microorganisms to be stimulated in vitro, opening a new field of application for electrospun polymers. A biphasic cultivation [37] in presence of nanofibers might support bacterial attachment and growth mimicking surface dehydration and particle microenvironments of soil in natural habitats.…”

“…The strong affinity for fibers might result from mutual electrostatic, hydrophobic interactions involving proteins forming the superficial layer of aerial hyphae. The density of the fibrous materials, related to the interconnected porosity of polymer nanofibers, which can reach values as high as 80–90%, also plays an important role, because it disfavors mycelia entanglements and formation of bacterial pellets, which cause suboptimal growth and production yields in SmF cultures (i.e., without solid substrates for cell adsorption) . In our samples, voids among fibers typically range around a few tens of μm, which well‐matches the size of pores (50–100 μm) requested for enhancing productivity .…”

Mechanical behavior of polylactic acid/polycaprolactone porous layered functional composites

“…Theoretical porosity, porosity and connectivity were calculated according to the following expressions [37]:…”

Using Taguchi method for the optimization of processing variables to prepare porous scaffolds by combined melt mixing/particulate leaching

“…Among biodegradable polymers of synthetic origin, poly(lactic acid) (PLA) has been extensively studied for several decades, thanks to its chemical-physical properties and easy processability [5,[12][13][14]. One of the most efficient plasticizers for PLA is poly(ethylene glycol) (PEG) hydrophilic and biocompatible polymer [13,[15][16][17][18].…”