Empirical and experimental determination of the kinetics of pellet growth in filamentous fungi: A case study using Neurospora intermedia

Abstract

Pellet morphology formation by filamentous fungi has gained a lot of attention because of its multiple benefits such as the ease of separation and smaller bioreactor volume requirement. Most reported kinetics studies on fungal pellet growth are centred on aeration, despite the experimental results pointing to the importance of other factors such as pH, substrates and product concentration etc., influencing the pellet formation. Hence a kinetic study on the effect of multiple factors such as aeration, substrate and product concentration and pH was done in this paper using Neurospora intermedia as a model organism, whose ability to form mycelial pellets was recently reported. The maximum growth rate of the pellets under uninhibited conditions at its optimal growth pH was 0.318h−1. The pellets were found to be inhibited by high product (ethanol) concentration with no growth occurring at 70gL−1 and above. High substrate concentration favoured the formation of loose fur-like fluffy pellets. The specific oxygen uptake rate of the pellets was between 0.27–0.9 mmol-O2 g-biomass−1h−1 depending on the pellet average diameter. The results from this kinetic study can be used for bioreactor design, operations and optimization of fermentation processes utilizing N. intermedia.