Effects of dissolved oxygen on fungal morphology and process rheoleogy during fed-batch processing of Ganoderma lucidum

Mariana L. Fazenda, Linda M. Harvey, Brian McNeil

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)

Abstract

Controlling the dissolved oxygen (DO) in the fed-batch culture of the medicinal mushroom Ganoderma lucidum led to a two-fold increase of the maximum biomass productivity compared to uncontrolled DO conditions. By contrast, extracellular polysaccharide (EPS) production was two times higher under oxygen limitation (uncontrolled DO) than under increased oxygen availability (controlled DO). Morphologically, dispersed mycelium was predominant under controlled DO conditions, with highly branched hyphae, consistent with the enhanced culture growth noted under these conditions. While in the uncontrolled DO processes mycelial clumps were the most common morphology throughout the culture. However, in both cultures clamp connections were found. This is an exciting new finding, which widens the applicability of this basidiomycete in submerged fermentation. In rheological terms, broths demonstrated shear-thinning behaviour with a yield stress under both DO conditions. The flow curves were best described by the Herschel-Bulkley model: flow index down to 0.6 and consistency coefficient up to 0.2 and 0.6 Pa sn in uncontrolled and controlled cultures DO, respectively. The pseudoplastic behaviour was entirely due to the fungal biomass, and not to the presence of EPS (rheological analysis of the filtered broth showed Newtonian behaviour). It is clear that dissolved oxygen tension is a critical process parameter that distinctly influences G. lucidum morphology and rheology, affecting the overall performance of the process. This study contributes to an improved understanding of the process physiology of submerged fermentation of G. lucidum.
Original languageEnglish
Pages (from-to)844-851
Number of pages8
JournalJournal of Microbiology and Biotechnology
Volume20
Issue number4
Publication statusPublished - Apr 2010

Keywords

  • dissolved oxygen
  • fungal morphology
  • process rheology
  • Ganoderma lucidum

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