Demirci A, Pometto A L, Ho K L
Department of Food Science and Human Nutrition, Iowa State University, Ames 50011, USA.
J Ind Microbiol Biotechnol. 1997 Oct;19(4):299-304. doi: 10.1038/sj.jim.2900464.
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.
生物膜是细胞固定化的自然形式，其中微生物附着在固体载体上。在爱荷华州立大学，我们开发了塑料复合载体（PCS）（农业材料（大豆壳或燕麦壳）、复合营养素和聚丙烯），它能刺激生物膜形成，并为附着的微生物提供营养。最初在低有机氮培养基中，用酿酒酵母（ATCC 24859）对各种PCS混合物进行重复分批培养管发酵评估。然后，将选定的PCS（40%大豆壳、5%大豆粉、5%酵母提取物盐和50%聚丙烯）用于在含降低氮含量的各种培养基中与选定的PCS进行连续和重复分批发酵。在连续发酵过程中，酿酒酵母在PCS生物反应器中的乙醇产量比单独使用聚丙烯载体（PPS）对照高两到十倍。在重复分批发酵中，酿酒酵母在含硫酸铵培养基的PCS上产生了30 g L-1乙醇，而PPS对照产生了5 g L-1乙醇。总体而言，使用这种新型生物反应器设计，在低成本培养基中可以实现超过传统发酵的更高生产率。
