The major challenges associated with the fermentation of lignocellulosic hydrolysates are the
reduction in the operating cost and minimizing the complexity of the process. Zymomonas mobilis
been emerged to resolve these complexities. Biofilm has been reported to tolerate to the toxic inhibitors and
easily manipulated toward the cell recycle through the cell immobilization.
ZM4 and TISTR 551 were able to develop biofilms on DEAE cellulose under the differences in the morphologies. Z. mobilis
ZM4 developed homogeneous biofilm that brought DEAE fiber to be crosslinking, while Z. mobilis
TISTR 551 developed heterogeneous biofilm in which crosslinking was not observed. Ethanol
production under batch and repeated batch fermentation of rice bran hydrolysate containing toxic inhibitors
were compared between these two biofilms. TISTR 551 biofilm produced the maximum yield (YP/S
) of 0.43 ±
0.09 g ethanol/g glucose (83.89% theoretical yield). However the repeated batch could not be proceeded due
to the bacterial detachment. Z. mobilis
ZM4 biofilm produced the maximum yield (YP/S
) of 0.177 ± 0.05 g ethanol/g glucose (34.74% theoretical yield) in the batch culture and the biofilm remained intact to proceed
along the repeated batch. The highest ethanol yield (YP/S) in the repeated batch of Z. mobilis
ZM4 was 0.354 ±
0.07 g ethanol/g glucose (69.51% theoretical yield).
Homogeneous biofilm structure of Z. mobilis
provided more recycle beneficial over the
heterogeneous biofilm structure for the ethanol production from lignocellulosic hydrolysate.