The filamentous fungal pellet—relationship between morphology and productivity

Abstract

Filamentous fungi are used for the production of a multitude of highly relevant biotechnological products like citric acid and penicillin. In submerged culture, fungi can either grow in dispersed form or as spherical pellets consisting of aggregated hyphal structures. Pellet morphology, process control and productivity are highly interlinked. On the one hand, process control in a bioreactor usually demands for compact and small pellets due to rheological issues. On the other hand, optimal productivity might be associated with less dense and larger morphology. Over the years, several publications have dealt with aforementioned relations within the confines of specific organisms and products. However, contributions which evaluate such interlinkages across several fungal species are scarce. For this purpose, we are looking into methods to manipulate fungal pellet morphology in relation to individual species and products. This review attempts to address (i) how variability of pellet morphology can be assessed and (ii) how morphology is linked to productivity. Firstly, the mechanism of pellet formation is outlined. Subsequently, the description and analysis of morphological variations are discussed to finally establish interlinkages between productivity, performance and morphology across different fungal species.

The entomopathogenic fungus Beauveria bassiana produces microsclerotia‐like pellets mediated by oxidative stress and peroxisome biogenesis

“…B. bassiana 4 day‐old granules had an average size of 815 ± 30 μm, with different sizes between 450 and 1350 μm (n = 40 granules measured). This pattern of microsclerotia development in B. bassiana is very similar to the noncoagulative model of pellet formation described in other filamentous fungi grown in submerged liquid cultures (Priegnitz et al ., ; Veiter et al ., ).…”

Biotransformation of struvite by Aspergillus niger: phosphate release and magnesium biomineralization as glushinskite

“…carbopol, polyacrylic acid) and genetic attributes of the particular fungal strain have all been implicated in pellet formation and structure (Fomina and Gadd, ). Depending on cultivation conditions, fungal species can exhibit different morphologies even for the same species (Gow et al, ; Veiter et al ., ). In this study, addition of struvite into the liquid medium altered the initial pH which might have been one factor influencing pellet formation.…”

“…In this study, addition of struvite into the liquid medium altered the initial pH which might have been one factor influencing pellet formation. At the initial steps in fungal development, electrostatic and hydrophobic interactions affect spore aggregation (Priegnitz et al ., ; Zhang and Zhang, ; Veiter et al ., ). For instance, conidia of A .…”

An X‐ray microtomography‐based method for detailed analysis of the three‐dimensional morphology of fungal pellets

“…Considering the three regions with high hyphal fractions, it can be supposed that the P. chrysogenum pellet was a product of the agglomeration of three hyphal clumps. This is a typical pellet-formation mechanism for filamentous microorganisms of the hyphal element agglomerating type, including P. chrysogenum (Nielsen, Johansen, Jacobsen, Krabben, & Villadsen, 1995;Veiter et al, 2018).…”

“…In fungal biotechnology, three pellet‐forming mechanisms are generally distinguished: coagulative, noncoagulative, and hyphal element agglomerating (Veiter, Rajamanickam, & Herwig, ). Coagulative formation comprises two steps.…”