TY - JOUR
T1 - Consortia-mediated bioprocessing of cellulose to ethanol with a symbiotic Clostridium phytofermentans/yeast co-culture
AU - Zuroff, Trevor R.
AU - Xiques, Salvador Barri
AU - Curtis, Wayne R.
N1 - Funding Information:
We are grateful to Dr. Jamie Cate at the University of California, Berkeley for providing Saccharomyces cereivisae strain cdt-1, Dr. Susan Leschine at the University of Massachusetts, Amherst for Clostridium phytofermentans ISDg10 and the USDA NRRL for Candida molischiana (Y-2237). We thank Patrick Hillery, Jessica Bigham and Taylor Maher who assisted in sample collection and analysis and Mark Signs who supported analytical work. We would like to thank Thomas K. Wood at The Pennsylvania State University for his comments on the research and manuscript. This material is based upon work done by TR Zuroff supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-0750756. TR Zuroff also received funding for this work from the Pennsylvania State University Department of Chemical Engineering John and Jeanette McWhirter Graduate Research Fellowship. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
PY - 2013
Y1 - 2013
N2 - Background: Lignocellulosic ethanol is a viable alternative to petroleum-based fuels with the added benefit of potentially lower greenhouse gas emissions. Consolidated bioprocessing (simultaneous enzyme production, hydrolysis and fermentation; CBP) is thought to be a low-cost processing scheme for lignocellulosic ethanol production. However, no single organism has been developed which is capable of high productivity, yield and titer ethanol production directly from lignocellulose. Consortia of cellulolytic and ethanologenic organisms could be an attractive alternate to the typical single organism approaches but implementation of consortia has a number of challenges (e.g., control, stability, productivity). Results: Ethanol is produced from α-cellulose using a consortium of C. phytofermentans and yeast that is maintained by controlled oxygen transport. Both Saccharomyces cerevisiae cdt-1 and Candida molischiana "protect" C. phytofermentans from introduced oxygen in return for soluble sugars released by C. phytofermentans hydrolysis. Only co-cultures were able to degrade filter paper when mono- and co-cultures were incubated at 30°C under semi-aerobic conditions. Using controlled oxygen delivery by diffusion through neoprene tubing at a calculated rate of approximately 8 μmol/L hour, we demonstrate establishment of the symbiotic relationship between C. phytofermentans and S. cerevisiae cdt-1 and maintenance of populations of 10§ssup§5§esup§ to 10§ssup§ 6§esup§ CFU/mL for 50 days. Comparable symbiotic population dynamics were observed in scaled up 500 mL bioreactors as those in 50 mL shake cultures. The conversion of α-cellulose to ethanol was shown to improve with additional cellulase indicating a limitation in hydrolysis rate. A co-culture of C. phytofermentans and S. cerevisiae cdt-1 with added endoglucanase produced approximately 22 g/L ethanol from 100 g/L α-cellulose compared to C. phytofermentans and S. cerevisiae cdt-1 mono-cultures which produced approximately 6 and 9 g/L, respectively. Conclusion: This work represents a significant step toward developing consortia-based bioprocessing systems for lignocellulosic biofuels production which utilize scalable, environmentally- mediated symbiosis mechanisms to provide consortium stability.
AB - Background: Lignocellulosic ethanol is a viable alternative to petroleum-based fuels with the added benefit of potentially lower greenhouse gas emissions. Consolidated bioprocessing (simultaneous enzyme production, hydrolysis and fermentation; CBP) is thought to be a low-cost processing scheme for lignocellulosic ethanol production. However, no single organism has been developed which is capable of high productivity, yield and titer ethanol production directly from lignocellulose. Consortia of cellulolytic and ethanologenic organisms could be an attractive alternate to the typical single organism approaches but implementation of consortia has a number of challenges (e.g., control, stability, productivity). Results: Ethanol is produced from α-cellulose using a consortium of C. phytofermentans and yeast that is maintained by controlled oxygen transport. Both Saccharomyces cerevisiae cdt-1 and Candida molischiana "protect" C. phytofermentans from introduced oxygen in return for soluble sugars released by C. phytofermentans hydrolysis. Only co-cultures were able to degrade filter paper when mono- and co-cultures were incubated at 30°C under semi-aerobic conditions. Using controlled oxygen delivery by diffusion through neoprene tubing at a calculated rate of approximately 8 μmol/L hour, we demonstrate establishment of the symbiotic relationship between C. phytofermentans and S. cerevisiae cdt-1 and maintenance of populations of 10§ssup§5§esup§ to 10§ssup§ 6§esup§ CFU/mL for 50 days. Comparable symbiotic population dynamics were observed in scaled up 500 mL bioreactors as those in 50 mL shake cultures. The conversion of α-cellulose to ethanol was shown to improve with additional cellulase indicating a limitation in hydrolysis rate. A co-culture of C. phytofermentans and S. cerevisiae cdt-1 with added endoglucanase produced approximately 22 g/L ethanol from 100 g/L α-cellulose compared to C. phytofermentans and S. cerevisiae cdt-1 mono-cultures which produced approximately 6 and 9 g/L, respectively. Conclusion: This work represents a significant step toward developing consortia-based bioprocessing systems for lignocellulosic biofuels production which utilize scalable, environmentally- mediated symbiosis mechanisms to provide consortium stability.
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U2 - 10.1186/1754-6834-6-59
DO - 10.1186/1754-6834-6-59
M3 - Article
C2 - 23628342
AN - SCOPUS:84876784021
SN - 1754-6834
VL - 6
JO - Biotechnology for Biofuels
JF - Biotechnology for Biofuels
IS - 1
M1 - 59
ER -