초록
<P><B>Abstract</B></P> <P>Submerged hollow fiber membrane bioreactor (SHFMB) was fabricated and operated to co-culture <I>Zymomonas mobilis</I> and <I>Scheffersomyces stipitis</I> for fermentation of glucose and xylose mixture. Suspended <I>Z. mobilis</I> and <I>S. stipitis</I> in co-culture exhibited poor xylose fermentation due to substrate/product inhibition and catabolite repression. Immobilization in polymeric membranes was effective in alleviating these inhibitions in the SHFMB, which resulted in concomitant fermentation of glucose and xylose at initial glucose and xylose concentrations of 20–80 g L<SUP>−1</SUP> and 10–40 g L<SUP>−1</SUP>, respectively. Selective aeration in SHFMB resulted in 100% glucose and >70% xylose fermentation within 48 h, producing 36.7 g L<SUP>−1</SUP> ethanol from 90 g L<SUP>−1</SUP> sugar mixture. Partial immobilization in the membranes allowed <I>Z. mobilis</I> to diffuse in suspension under benign condition, whereas <I>S. stipitis</I> remained inside membrane pores throughout the operation. Xylose fermentation in the SHFMB could be enhanced further by increasing the number of <I>S. stipitis</I> immobilized membranes. Cell immobilization in the SHFMB was stable during 12 consecutive batch runs over 24 days, and exhibited improved xylose fermentation due to gradual increase in <I>S. stipitis</I> accumulation within the membranes. These results indicate that SHFMB can be promising for co-culture of <I>Z. mobilis</I> and <I>S. stipitis</I> in fermentation of mixed sugars from lignocellulosic hydrolysate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Submerged hollow fiber membrane bioreactor (SHFMB) was developed. </LI> <LI> Co-culture of immobilized and suspended <I>Z. mobilis</I> and <I>S. stipitis</I> was conducted. </LI> <LI> SHFMB alleviated catabolite repression, substrate and product inhibition. </LI> <LI> Concomitant glucose and xylose fermentation was observed in the SHFMB. </LI> <LI> Cell immobilization in SHFMB was stable and performance improved with time. </LI> </UL> </P>