High‐energy X‐ray tomography analysis of a metal packing biofilm reactor for the production of lipopeptides byBacillus subtilis

Abstract

BACKGROUND Whereas multi‐species biofilm reactors are commonly used for the treatment of liquid and solid wastes, new strategies are progressing for the development of single species biofilm for the production of high‐value metabolites. Technically, this new concept relies on the design of bioreactors able to promote biofilm formation and on the identification of the key physico‐chemical parameters involved in biofilm formation. RESULTS An experimental setting comprising a liquid continuously recirculated on a metal structured packing has been used to promote Bacillus subtilis GA1 biofilm formation. The colonization of the packing has been visualized non‐invasively by X‐ray tomography. This analysis revealed an uneven, conical, distribution of the biofilm inside the packing. Compared with a submerged culture carried out in a stirred tank reactor, significant modification of the lipopeptide profile has been observed in the biofilm reactor with the disappearance of fengycin and iturin fractions and an increase of the surfactin fraction. In addition, considering the biofilm reactor design, no foam formation has been observed during the culture. CONCLUSIONS The configuration of this biofilm reactor set‐up allows for a higher surfactin production by comparison with a submerged culture while avoiding foam formation. Additionally, scale‐up could easily be performed by increasing the number of packing elements. © 2013 Society of Chemical Industry

Pathogenicity of <i>Aspergillus clavatus</i> produced in a fungal biofilm bioreactor toward <i>Culex quinquefasciatus</i> (Diptera: Culicidae)

“…Packing is a cylinder composed of several stainless steel corrugated sheets independent of each other, as previously described. 23) For packing, 28 metal rectangular plates (16×16 to 2×16 cm) with a 2-mm mesh were cut for assembly. The plates were superimposed symmetrically in pairs following the decreasing width of the rectangle in order to form a cylinder approximately 16 cm in diameter.…”

A fungal biofilm reactor based on metal structured packing improves the quality of a Gla::GFP fusion protein produced by Aspergillus oryzae

“…High-energy X-ray tomography was found to be a useful tool for visualizing and quantifying the fungal biomass in the BfRs. This technique has demonstrated its performance for the characterization of similar processes in previous studies (Aferka et al 2011;Zune et al 2013). Indeed, it provides relevant information about the effect of hydrodynamic conditions on biofilm distribution inside the metal structured packing.…”

“…Tomographic measurements were performed on 16 different cross-sectional areas located at different heights (analysis is performed every 5 mm). The experimental method for tomographic measurements and subsequent treatment for absorption coefficient processing and image analysis have been previously described (Aferka et al 2011;Zune et al 2013). …”

“…Although the structure of filamentous fungi biofilms has been previously investigated at the micro-scale level by confocal laser scanning microscopy and cryo-scanning electron microscopy , the macro-scale characterization of biofilms inside process equipment had not been previously considered. In this work, large-scale X-ray tomography analysis will be used for the non-invasive visualization of the biofilm structure inside the bioreactor (Aferka et al 2011;Zune et al 2013). This bioreactor will be used for the production of recombinant protein by Aspergillus oryzae.…”

Recent Advances in Fungal Hydrophobin Towards Using in Industry

“…To overcome this, the use of biofilm reactor has been suggested [26]. Higher fermentation productivity, higher end concentration of products, higher product stability, lower demand of sterility, and the possibility of the operation in continuous mode, are the advantages of this set-up [57]. Using a biofilm reactor has been reported to cause a significant increase of hydrophobin HFBII up to 80 % and in shorter time, in comparison with a classical submerged bioreactor [26].…”