Abstract
An effective method for research of macro-morphological characterization and its kinetics was developed by studying the macro-morphological characteristics of Mortierella alpina, an oleaginous zygomycete widely used to produce lipids rich in PUFA, in function of culture medium composition and to link morphological features of fungus with the level of lipid production. A number of distinct morphological forms including hollow pellets, fluffy pellets and freely dispersed mycelia were obtained by changing the fermentation factors. By fitting a Logistic curve, the maximum specific growth rate (μmax)was obtained, which determined the final mycelia morphology. μmax of 0.6584 in three kind of morphological forms is the more appropriate. According to the Luedeking-Piret equation fitting, α≠0 and β≠0, lipid production was partially associated with the hyphal growth, fluffy pellets which turn glucose into lipidwas more effective than the other two kinds of morphological forms.
Highlights
Microbial lipophilic compounds, called single cell oils (SCO), are potentially interesting to the food and pharmaceutical industries owing to their specific characteristics [1,2]
During the optimization of fermentation conditions for polyunsaturated fatty acids (PUFA) production, we found that the culture medium component could influence the macro-morphology of Mortierella alpina
Increasing the glucose concentration to 100 g/L, M. alpina appeared as pellets but the mycelia were slender (Fig 1A).The reason for slender hyphae is that high concentrations of glucose cause excessive osmotic pressure in fermentation broth, which lead to intracellular water molecules leakage, further affecting the mycelial growth
Summary
Microbial lipophilic compounds, called single cell oils (SCO), are potentially interesting to the food and pharmaceutical industries owing to their specific characteristics [1,2]. When grown in submerged culture, filamentous fungi are able to develop complex morphologies, which have been classified into three major groups: pellets, mycelia aggregates (so called clumps) and freely dispersed mycelia [8,9,10]. Studies addressing the morphology and physiology of fungi in liquid cultures have been reviewed [11,12,13], which showed fungal morphology played a significant role on medium rheology, and thereby affecting the mixing and mass transfer within the bioreactor, and influenced metabolite activity, resulting in either
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