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The influence of salt-enhanced cultivation on the micromechanical behaviour of filamentous pellets

Dittmann, Johannes, Tesche, Sebastian, Krull, Rainer, Böl, Markus
Biochemical engineering journal 2019 v.148 pp. 65-76
Actinomadura, Aspergillus niger, ammonium sulfate, enzymes, mechanical properties, microorganisms, mycelium, pellets, secondary metabolites, sodium chloride
Micromechanical properties are important indicators for pellet formation of filamentous microorganisms in biotechnological processes. Therefore, the pellet's morphology plays a key role, as its shape and the mechanical characteristics influence the production efficacy of biotechnological processes. Current investigations focus on characterisation of the pellet's mechanical behaviour as a function of its geometrical size. While the cultivation of filamentous pellets of Aspergillus niger SKAn1015 and Actinomadura namibiensis showed improved production performances for the enzyme fructofuranosidase and the secondary metabolite labyrinthopeptin A1, respectively, under various salt-enhanced cultivation (SEC) conditions micromechanical plate compression experiments were performed. A. niger was cultivated with 0 and 500 mM NaCl and A. namibiensis was cultivated with 0 and 50 mM (NH4)2SO4. While the results with A. niger showed little difference after the addition of NaCl to the cultivation broth, the treatment of A. namibiensis with 0 mM (NH4)2SO4 resulted in optically dense pellets, leading to stiffer mechanical behaviour than that observed under 50 mM (NH4)2SO4 cultivation. Mechanical properties could be used to monitor the production-specific properties of these mycelial objects, motivating further research in this area.