초록
<P><B>Background</B></P><P>Consolidated bioprocessing (CBP) of butanol production from cellulosic biomass is a promising strategy for cost saving compared to other processes featuring dedicated cellulase production. CBP requires microbial strains capable of hydrolyzing biomass with enzymes produced on its own with high rate and high conversion and simultaneously produce a desired product at high yield. However, current reported butanol-producing candidates are unable to utilize cellulose as a sole carbon source and energy source. Consequently, developing a co-culture system using different microorganisms by taking advantage of their specific metabolic capacities to produce butanol directly from cellulose in consolidated bioprocess is of great interest.</P><P><B>Results</B></P><P>This study was mainly undertaken to find complementary organisms to the butanol producer that allow simultaneous saccharification and fermentation of cellulose to butanol in their co-culture under mesophilic condition. Accordingly, a highly efficient and stable consortium N3 on cellulose degradation was first developed by multiple subcultures. Subsequently, the functional microorganisms with 16S rRNA sequences identical to the denaturing gradient gel electrophoresis (DGGE) profile were isolated from consortium N3. The isolate <I>Clostridium celevecrescens</I> N3-2 exhibited higher cellulose-degrading capability was thus chosen as the partner strain for butanol production with <I>Clostridium acetobutylicum</I> ATCC824. Meanwhile, the established stable consortium N3 was also investigated to produce butanol by co-culturing with <I>C. acetobutylicum</I> ATCC824. Butanol was produced from cellulose when <I>C. acetobutylicum</I> ATCC824 was co-cultured with either consortium N3 or <I>C. celevecrescens</I> N3-2. Co-culturing <I>C. acetobutylicum</I> ATCC824 with the stable consortium N3 resulted in a relatively higher butanol concentration, 3.73 g/L, and higher production yield, 0.145 g/g of glucose equivalent.</P><P><B>Conclusions</B></P><P>The newly isolated microbial consortium N3 and strain <I>C. celevecrescens</I> N3-2 displayed effective degradation of cellulose and produced considerable amounts of butanol when they were co-cultured with <I>C. acetobutylicum</I> ATCC824. This is the first report of application of co-culture to produce butanol directly from cellulose under mesophilic condition. Our results indicated that co-culture of mesophilic cellulolytic microbe and butanol-producing clostridia provides a technically feasible and more simplified way for producing butanol directly from cellulose.</P>