Influence of different magnetites on properties of magnetic Pseudomonas aeruginosa immobilizates used for biosurfactant production

Abstract

During the last decades, whole-cell immobilization has been used successfully in many bioprocesses. In particular, it is aimed at implementing continuous production processes, reaching higher production rates, and reusing the biocatalyst. In some cases, effective retention of immobilizates in the bioprocess is not feasible by membranes or sieves due to pore plugging or undesired losses of immobilizates. In the present publication, it is reported about the investigation of magnetic immobilizates of Pseudomonas aeruginosa for application in continuous biosurfactant production of rhamnolipids by foam fractionation and retention of entrained immobilizates by high-gradient magnetic separation from foam. Different materials and methods were tested with respect to important parameters, such as stability, diffusion properties or magnetic separation. Good magnetic separation of immobilizates was achieved at 5% (w/w) magnetite loading. Best results in terms of homogeneous embedding, good diffusion properties, and stability enhancement vis-à-vis pure alginate beads was achieved with alginate beads with embedded Bayoxide magnetite or MagPrep silica particles. Although polyurethane immobilizates showed higher stabilities compared with alginate beads, rhamnolipid diffusion in immobilizates was superior in magnetic alginate beads. Regarding bead production, smaller immobilizates were achieved with suspension polymerization compared to droplet extrusion by the JetCutting technology. In total, magnetic immobilizates are a promising tool for an easier handling of biocatalysts in a continuous biological production process, but they have to be adapted to the current production task.

Microwave enhanced silica encapsulation of magnetic nanoparticles

“…5b) to external fields, which implies usefulness for various bioapplications including magnetically assisted cell separation, 36 drug delivery 37 and removal of micro-organisms. 38 The size of our products is comparable to commercially available magnetic nanoparticles with silica surface, such as SiMAG (0.5 mm to 1 mm size, Chemicell), BcMagÔ (1 mm size, Bioclone) and MagPrep Ò (0.1mm size, Merck), having $26, 39 40 40 and 88 emu/g composite, 41 respectively, which are used for magnetic bioseparation.…”

Continuous rhamnolipid production with integrated product removal by foam fractionation and magnetic separation of immobilized Pseudomonas aeruginosa

“…The produced immobilizates had a particle size distribution ranging from about 30 μm to 640 μm (for 95% of beads) with a medium volume‐related particle size of ∼240 μm ( x AV , 50 ). The initial specific saturation magnetization of the humid immobilizates was ∼5 A m 2 kg −1 and, hence, more than sufficient for magnetic separation in a high‐gradient magnetic separator 40…”

Chemically modified nanoparticles surface for sensing bacterial loading—experimental study based on fluorescence stimulation by iron ions

“…The interaction of Pseudomonas bacteria and iron ions from magnetic nanoparticles has been studied by several research teams focused on the magnetite nanoparticle antimicrobial features [18][19][20], while others developed some biotechnological applications. Liu et al(2009) have proposed a method for targeting bacteria from clinical samples based on the interaction between the galactophilic lecithin from P. aeruginosa membrane receptors and the magnetic nanoparticles coated with phosphoproteic containing Galα(1-4)Gal units [21], while Heyd et al(2009) reported on the investigation of magnetic immobilizates of P. aeruginosa on magnetite for the application in continuous biosurfactant production of rhamnolipids [22]. Pseudomonas delafieldii labeled with magnetic Fe 3 O 4 /ammonium oleate nanoparticles and immobilized by external magnetic field was found able of greater desulfurization activity than free cells or cells immobilized on celite (Shan et al, 2005) [23].…”