Accelerated bioethanol fermentation by using a novel yeast immobilization technique: Microtube array membrane

Cell immobilization is a way to isolate or localize intact cells in a certain space and maintain their catalytic activity. Immobilized cells can effectively reduce the negative effects of inhibitors and the processing cost of inoculum preparation for continuous or fed-batch fermentation of microorganisms. In this study, a novel yeast immobilization technique using renewable poly-l-lactic acid (PLLA) microtube array membrane (MTAM) was thoroughly evaluated for bioethanol fermentation. PLLA-MTAM was shown to be stable in 15% (v/v) ethanol solution during shaking cultivation. A yeast encapsulation efficiency of 67-70% was obtained, and the yeasts in MTAMs with greater porosity showed greater bioethanol productivity. The MTAM-immobilized Kluyveromyces marxianus, prepared using in situ and siphon methods, were evaluated using 5% (w/v) glucose fermentation. Improved glucose consumption and bioethanol production were observed in batch bioethanol fermentation. In 7 cycles during repeated-batch fermentation, the immobilized yeasts prepared using the in situ method showed a maximum C_EtOH of 24.23 g/L, maximum Y_P/S of 0.48 g/g, and r P_EtOH of 2.69 g/L h. Our data indicated that the PLLA-MTAM immobilized yeasts significantly enhanced bioethanol productivity and was a novel, promising technology for bioethanol fermentation.