Ethanol production by Saccharomyces cerevisiae in biofilm reactors

Abstract

Biofilms are natural forms of cell immobilization in which microorganisms attach to solid supports. At ISU, we have developed plastic composite-supports (PCS) (agricultural material (soybean hulls or oat hulls), complex nutrients, and polypropylene) which stimulate biofilm formation and which supply nutrients to the attached microorganisms. Various PCS blends were initially evaluated in repeated-batch culture-tube fermentation with Saccharomyces cerevisiae (ATCC 24859) in low organic nitrogen medium. The selected PCS (40% soybean hull, 5% soybean flour, 5% yeast extract-salt and 50% polypropylene) was then used in continuous 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. cerevisiae 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 low cost medium can be achieved beyond conventional fermentations using this novel bioreactor design.

Bioprocess Intensification for Production of Novel Marine Bacterial Antibiotics Through Bioreactor Operation and Design

“…Novel engineered support materials are being developed to improve immobilized bioprocesses, such as a nutrient-containing "plastic composite support," which outperforms normal polypropylene supports in ethanol production (Demirci et al, 1997). Another new support constructed from metal mesh particles aims to reduce the high shear stress sometimes suffered by immobilized bacteria (Kargi and Toprak, 1994).…”

Potential Production of Ethanol by Saccharomyces cerevisiae Immobilized and Coimmobilized with Zymomonas mobilis: Alternative for the Reuse of a Waste Organic

“…Fermentation was performed in a Chemostat Ommi Culture Plus (Virtis) with a volume of 2 L operation, adjusting stirring at 120 rpm and maintaining a temperature of 30°C. The medium equivalent to mango juice was similar to that described by Demirci et al [25] by adjusting the composition of the medium to a concentration of 200 g L −1…”

“…Nevertheless, there was greater productivity, which indicates that it is possible to obtain high alcohol content with a lower requirement of substrate, but with the disadvantage of residual glucose in the medium; this problem can be solved with sequenced systems, as suggested by Demirci et al [25]. Another alternative of solving this problem is to increase the cell number or inoculum size within the reactor.…”

Enhanced pullulan production in a biofilm reactor by using response surface methodology

“…Plastic composite support (PCS) has been developed to provide an ideal surface for biofilm formation, which is an extrusion product of a mixture of polypropylene and nutritious compounds [28]. Many studies have shown that PCS biofilm reactors can enhance production of ethanol [13], organic acid [36], and bacterial cellulose [11]. Moreover, the slow release of the ingredients on PCS, such as carbon sources, nitrogen sources, and minerals, can persist for more than 1 year without affecting its efficiency when performing continuous fermentation [12,13,18].…”