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D M Stuart

Publications and source records attributed to D M Stuart.

3 recordsLinked to original sources
PubMed1999

Response of Rhizopus oligosporus to temporal temperature profiles in a model solid-state fermentation system.

Membrane overcultures of Rhizopus oligosporus were shifted from 37 to 50 degrees C for 10 h and then returned to 37 degrees C, mimicking the temporal temperature profiles which typically occur in SSF due to heat transfer limitations. Analysis with a modified two-phase growth model suggests that the temperature upshift causes a 48% decrease in the number of actively extending hyphal tips, and that the first order death rate constant of tips increases from 0. 059 to 0.073 h(-1). The fungus did not immediately recover when the temperature was returned to 37 degrees C. The model assumed that the specific growth rate constant microgram(g) was not affected by the increase of temperature, although contradictory data was obtained from radial growth rate experiments.

Cell Division↗
PubMed1999

Solid-state fermentation in rotating drum bioreactors: operating variables affect performance through their effects on transport phenomena.

Aspergillus oryzae ACM 4996 was grown on an artificial gel-based substrate and on steamed wheat bran during solid-state fermentations in 18.7 L rotating drum bioreactors. For gel fermentations fungal growth decreased as rotational speed increased, presumably due to increased shear. For wheat bran fermentations fungal growth improved under agitated compared to static culture conditions, due to superior heat and mass transfer. We conclude that the effects of operational variables on the performance of SSF bioreactors are mediated by their effects on transport phenomena such as mixing, shear, heat transfer, and mass transfer within the substrate bed. In addition, the substrate characteristics affect the need for and the rates of these transport processes. Different transport phenomena may be rate limiting with different substrates. This work improves understanding of the effects of bioreactor operation on SSF performance.

Aspergillus oryzae↗