Morphological growth pattern of Phanerochaete chrysosporium cultivated on different Miscanthus x giganteus biomass fractions

Abstract

Background Solid-state fermentation is a fungal culture technique used to produce compounds and products of industrial interest. The growth behaviour of filamentous fungi on solid media is challenging to study due to the intermixity of the substrate and the growing organism. Several strategies are available to measure indirectly the fungal biomass during the fermentation such as following the biochemical production of mycelium-specific components or microscopic observation. The microscopic observation of the development of the mycelium, on lignocellulosic substrate, has not been reported. In this study, we set up an experimental protocol based on microscopy and image processing through which we investigated the growth pattern of Phanerochaete chrysosporium on different Miscanthus x giganteus biomass fractions. Results Object coalescence, the occupied surface area, and radial expansion of the colony were measured in time. The substrate was sterilized by autoclaving, which could be considered a type of pre-treatment. The fastest growth rate was measured on the unfractionated biomass, followed by the soluble fraction of the biomass, then the residual solid fractions. The growth rate on the different fractions of the substrate was additive, suggesting that both the solid and soluble fractions were used by the fungus. Based on the FTIR analysis, there were differences in composition between the solid and soluble fractions of the substrate, but the main components for growth were always present. We propose using this novel method for measuring the very initial fungal growth by following the variation of the number of objects over time. Once growth is established, the growth can be followed by measurement of the occupied surface by the mycelium. Conclusion Our data showed that the growth was affected from the very beginning by the nature of the substrate. The most extensive colonization of the surface was observed with the unfractionated substrate containing both soluble and solid components. The methodology was practical and may be applied to investigate the growth of other fungi, including the influence of environmental parameters on the fungal growth.

Easy-to-set-up image analysis characterizes phenotypic diversity in the growth of mushroom-forming fungusSchizophyllum commune

“…1b). From this observation, whiteness was also suggested as an index of growth, while area and/or diameter have been traditionally used as a growth index in fungal studies (Khalil et al, 2021; Ryan et al, 2012). We observed clear differences between strains in terms of area and whiteness of mycelial growth even on the same glucose concentration (for instance, see 37°C-High in Fig.…”

“…For instance, mycelia that are translucent and difficult to automatically detect in terms of area may have low cell density, which can be verified by counting cell numbers under a microscope. In fungi, some methods that quantify proliferation from a single spore have already been reported (Khalil et al, 2021; Ulzurrun et al, 2019; Zhang et al, 2022). However, we could not use these previous methods since we transplanted sections of mycelium that had proliferated from a single spore and thus took replicates from clones.…”

“…The growth of the mycelia of fungi is more difficult to capture than the growth of unicellular microbes because a mycelum forms complex structure on a solid medium (Khalil et al, 2021). Some experimental systems measure the growth patterns of mycelia proliferating from spores through live imaging systems (Khalil et al, 2021;Ulzurrun, Huang, Chang, Lin, & Hsueh, 2019;Zhang et al, 2022). However, live imaging systems require single-spore isolation for each experiment (i.e., the necessity to induce sexual reproduction and cycle generations), and live imaging involves expensive equipment, making it impractical for routine clinical testing.…”

“…Once a single spore can be isolated from a fruiting body in the laboratory, it allows for the establishment of genetically clonal mycelial cultures as strains similar to other microbial studies. The development of image analysis methods in microbiological research has been remarkably advanced, with many studies that target counting the number of cells or areas and diameters of colonies and biofilm in microbes(Khalil, Legin, Kurek, Perre, & Taidi, 2021; Ryan et al, 2012; Takeuchi et al, 2014; Zhang et al, 2022). The growth of the mycelia of fungi is more difficult to capture than the growth of unicellular microbes because a mycelum forms complex structure on a solid medium(Khalil et al, 2021).…”

“…The development of image analysis methods in microbiological research has been remarkably advanced, with many studies that target counting the number of cells or areas and diameters of colonies and biofilm in microbes(Khalil, Legin, Kurek, Perre, & Taidi, 2021; Ryan et al, 2012; Takeuchi et al, 2014; Zhang et al, 2022). The growth of the mycelia of fungi is more difficult to capture than the growth of unicellular microbes because a mycelum forms complex structure on a solid medium(Khalil et al, 2021). Some experimental systems measure the growth patterns of mycelia proliferating from spores through live imaging systems(Khalil et al, 2021; Ulzurrun, Huang, Chang, Lin, & Hsueh, 2019; Zhang et al, 2022).…”