Fermentation of rice bran hydrolysate to ethanol using Zymomonas mobilis biofilm immobilization on DEAE-cellulose

Abstract

Background: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 biofilm has 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. Results: Z. mobilis 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 (Y P/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 (Y P/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 (Y P/S ) in the repeated batch of Z. mobilis ZM4 was 0.354 ± 0.07 g ethanol/g glucose (69.51% theoretical yield). Conclusions: Homogeneous biofilm structure of Z. mobilis provided more recycle beneficial over the heterogeneous biofilm structure for the ethanol production from lignocellulosic hydrolysate.

Progress and perspective on lignocellulosic hydrolysate inhibitor tolerance improvement in Zymomonas mobilis

“…Recent studies showed that Z. mobilis biofilm cells exhibited a higher survival rate and metabolic activity than planktonic or free cells, which can also be developed and applied for the production of valuable bioproducts from toxic lignocellulosic hydrolysates (Li et al 2006;Todhanakasem et al 2014Todhanakasem et al , 2015Todhanakasem et al , 2018.…”

Artificial cordyceps mycelium by submerged fermentation of Hirsutella sinensis HS 1201 using rice bran hydrolysate as substrate

“…The mannitol and polysaccharides were generally increased with the increase of RBH dosage. The increasing polysaccharide production in CM was caused by the abundance of sugars in RBH that can be used as carbon sources for fungus (Todhanakasem et al., 2015).…”

Development of corn silk as a biocarrier for <i>Zymomonas mobilis</i> biofilms in ethanol production from rice straw

“…This work also documented increases in the immobilized cell concentrations for Z. mobilis biofilms on delignified corn silk and increased ethanol productivity in fermentations. Many different abiotic substrates have been used as immobilizers for Z. mobilis in the production of bioethanol, including glass beads, anionic exchangers and polypropylene composite agricultural waste (Krug and Daugulis, 1983;Kunduru and Pometto Iii, 1996;Todhanakasem et al, 2015;Weuster-Botz et al, 1993). The present study is unique in that it is the first work to show the biofilm structure and biofilm forming ability of Z. mobilis on agricultural material, as well as illustrating the potential for enhanced ethanol production from lignocellulosic hydrolysate.…”