Effects of dissolved oxygen tension and mechanical forces on fungal morphology in submerged fermentation

Abstract

The effects of dissolved oxygen tension and mechanical forces on fungal morphology were both studied in the submerged fermentation of Aspergillus awamori. Pellet size, the hairy length of pellets, and the free filamentous mycelial fraction in the total biomass were found to be a function of the mechanical force intensity and to be independent of the dissolved oxygen tension provided that the dissolved oxygen tension was neither too low (5%) nor too high (330%). When the dissolved oxygen concentration was close to the saturation concentration corresponding to pure oxygen gas, A. awamori formed denser pellets and the free filamentous mycelial fraction was almost zero for a power input of about 1 W/kg. In the case of very low dissolved oxygen tension, the pellets were rather weak and fluffy so that they showed a very different appearance. The amount of biomass per pellet surface area appeared to be affected only by the dissolved oxygen tension and was proportional to the average dissolved oxygen tension to the power of 0.33. From this it was concluded that molecular diffusion was the dominant mechanism for oxygen transfer in the pellets and that convection and turbulent flow in the pellets were negligible in submerged fermentations. The biomass per wet pellet volume increased with the dissolved oxygen tension and decreased with the size of the pellets. This means that the smaller pellets formed under a higher dissolved oxygen tension had a higher intrinsic strength. Correspondingly, the porosity of the pellets was a function of the dissolved oxygen tension and the size of pellets. Within the studied range, the void fraction in the pellets was high and always much more than 50%.

Agitation effects on morphology and protein productive fractions of filamentous and pelleted growth forms of recombinant Aspergillus niger

“…The morphology of Aspergillus, filamentous growth forms and/or the shape and size of pelleted growth forms as well as the branching frequency, is influenced by many factors including specific strain properties [22] but also environmental factors such as spore numbers in the inoculum or type of inoculum [23][24][25], medium composition [23,[26][27][28], dissolved oxygen concentration [29][30][31], pH [23,32], temperature [23,27], reactor type and scale [27,33], and power input [23,25,26,28,29,[33][34][35][36].…”

Ultrasound-intensified laccase production from Trametes versicolor

“…However, pelleted growth may limit the transfer of substrates and oxygen in the core of the pellet [28]. Therefore, in this study, we evaluated the pellet porosity (Fig.…”

Estimativa Da Velocidade De Cisalhamento Em Diferentes Modelos E Escalas De Biorreatores Pneumáticos Operados Com Fluidos Não-Newtonianos

“…Tais campos de cisalhamento mesmo em baixos níveis podem afetar a morfologia celular (Jonczyk et al, 2013), formação de pellets e biofilmes (Cui et al, 1998) e instabilidade mecânica de biocatalisadores imobilizados (Martins et al, 1997). Tais influências refletem em aspectos industrialmente importantes como a produtividade, produtos gerados e suas características (Chisti, 2009).…”