Influence of Morphology on Product Formation in Aspergillusawamori during Submerged Fermentations

Abstract

The relationship between fungal morphology and heterologous protein production was examined for an Aspergillus awamori strain during a series of fermentations with a batch phase followed by a fed-batch phase. Agitation rate and inoculation concentration were used as controlled variables to generate different fungal morphologies in 20-dm3 stirred tank reactors. Morphology was quantitatively characterized using Image Analysis. The different agitation rates and inoculum concentrations had large effects on the development in hyphal length and number of tips during the fermentations. A reduced inoculum concentration resulted in a more branched mycelium. The different agitation rates affected the morphology after 30 h of fermentation significantly but did not affect the start time of fragmentation. A 3-fold increase in hyphal length increased the apparent viscosity by a factor of 7. The observed morphological differences had only a limited effect on product formation, suggesting that the structural features such as hyphal length and number of tips are of less importance for product formation. The primary effect of morphology on product formation is due to viscosity.

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].…”

“…In particular, power input or agitation intensity has been identified as an important variable influencing the fungal morphology and productivity in recombinant Aspergillus protein production processes [25,28,[37][38][39]. In general, increasing power input changes the growth morphology from pelleted to filamentous growth forms.…”

“…For example, power input greatly influenced morphology and extracellular hen egg white lysozyme production by recombinant Aspergillus niger with highest productivities obtained at intermediate agitation speed in batch culture [37]. On the other hand, production of an extracellular cutinase by recombinant Aspergillus awamori was found to be independent on the agitation intensity in fed-batch cultures [25]. Also, production of extracellular amyloglucosidase by recombinant Aspergillus oryzae was reported to be independent on power input variations in chemostat cultures at constant dilution rate [38].…”

Metabolic Engineering of the Morphology of Aspergillus oryzae by Altering Chitin Synthesis

“…In microscopic morphology, single hyphal elements or hyphal populations are characterized by measuring their dimensions, such as total hyphal length, number of tips, hyphal diameter, number of nuclei per cell (20), and number of membranous organelles per cell (1). Recently, there has also been considerable effort to deduce the kinetics of submerged growth and branching (8,16,28,29), adding important details to the understanding of hyphal growth.The relationship between the mycelial morphology and the rheological properties of the cultivation medium has been the subject of a number of studies (2,15,19,25). The hyphal length per branch (length of the hyphal growth unit [l HGU ]) affects the overall morphology (34); a low l HGU has been associated with the formation of clumps smaller than those formed at a high l HGU (2).…”

Fermentation of Groundnut Shell Enzymatic Hydrolysate for Fuel Ethanol Production by Free and Sorghum Stalks Immobilized Cells of <em>Pichia stipitis</em> NCIM 3498

“…The higher ethanol yield up to 5 fermentation cycles is probably due to the higher utilization of sugars (95-98%) because of high cell density present in Sorghum stalks. The difference in ethanol productivity may also be attributed to the different environment and morphology of free and immobilized yeast cell mass and its effects on apparent viscosity that alters mass transfer and mixing characteristics (Johansen et al, 1998). In the present study, ethanol production was almost constant up to 5th cycle (Fig.…”