A. Demirci et al., ETHANOL-PRODUCTION BY SACCHAROMYCES-CEREVISIAE IN BIOFILM REACTORS, Journal of industrial microbiology & biotechnology, 19(4), 1997, pp. 299-304
Biofilms are natural forms of cell immobilization in which microorgani
sms attach to solid supports, At ISU, we have developed plastic compos
ite-supports (PCS) (agricultural material (soybean hulls or oat hulls)
, complex nutrients, and polypropylene) which stimulate biofilm format
ion and which supply nutrients to the attached microorganisms, Various
PCS blends were initially evaluated in repeated-batch culture-tube fe
rmentation with Saccharomyces cerevisiae (ATCC 24859) in low organic n
itrogen medium. The selected PCS (40% soybean hull, 5% soybean flour,
5% yeast extract-salt and 50% polypropylene) was then used in continuo
us and repeated-batch fermentation in various media containing lowered
nitrogen content with selected PCS. During continuous fermentation, S
. cerevisiae demonstrated two to 10 times higher ethanol production in
PCS bioreactors than polypropylene-alone support (PPS) control, S. ce
revisiae produced 30 g L-1 ethanol on PCS with ammonium sulfate medium
in repeated batch fermentation, whereas PPS-control produced 5 g L-1
ethanol, Overall, increased productivity in row cost medium can be ach
ieved beyond conventional fermentations using this novel bioreactor de
sign.