TY - JOUR
T1 - Alleviation of carbon catabolite repression in Enterobacter aerogenes for efficient utilization of sugarcane molasses for 2,3-butanediol production
AU - Jung, Moo Young
AU - Jung, Hwi Min
AU - Lee, Jinwon
AU - Oh, Min Kyu
N1 - Funding Information:
This study was supported by the R&D program of MKE/KEIT (No. 10035578, Development of 2,3‑butanediol and derivate production technology for C‑Zero bio‑platform industry) and the New & Renewable Energy Core Technol‑ ogy Program of the Korea Institute of Energy Technology Evaluation and Plan‑ ning (KETEP), granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea. (No. 20143030091040).
Publisher Copyright:
© 2015 Jung et al.
PY - 2015/7/31
Y1 - 2015/7/31
N2 - Background: Due to its cost-effectiveness and rich sugar composition, sugarcane molasses is considered to be a promising carbon source for biorefinery. However, the sugar mixture in sugarcane molasses is not consumed as efficiently as glucose in microbial fermentation due to complex interactions among their utilizing pathways, such as carbon catabolite repression (CCR). In this study, 2,3-butanediol-producing Enterobacter aerogenes was engineered to alleviate CCR and improve sugar utilization by modulating its carbon preference. Results: The gene encoding catabolite repressor/activator (Cra) was deleted in the genome of E. aerogenes to increase the fructose consumption rate. However, the deletion mutation repressed sucrose utilization, resulting in the accumulation of sucrose in the fermentation medium. Cra regulation on expression of the scrAB operon involved in sucrose catabolism was verified by reverse transcription and real-time PCR, and the efficiency of sucrose utilization was restored by disrupting the scrR gene and overexpressing the scrAB operon. In addition, overexpression of the ptsG gene involved in glucose utilization enhanced the glucose preference among mixed sugars, which relieved glucose accumulation in fed-batch fermentation. In fed-batch fermentation using sugarcane molasses, the maximum titer of 2,3-butanediol production by the mutant reached 140.0 g/L at 54 h, which was by far the highest titer of 2,3-butanediol with E. aerogenes achieved through genetic engineering. Conclusions: We have developed genetically engineered E. aerogenes as a 2,3-butanediol producer that efficiently utilizes sugarcane molasses. The fermentation efficiency was dramatically improved by the alleviation of CCR and modulation of carbon preference. These results offer a metabolic engineering approach for achieving highly efficient utilization of mixed sugars for the biorefinery industry.
AB - Background: Due to its cost-effectiveness and rich sugar composition, sugarcane molasses is considered to be a promising carbon source for biorefinery. However, the sugar mixture in sugarcane molasses is not consumed as efficiently as glucose in microbial fermentation due to complex interactions among their utilizing pathways, such as carbon catabolite repression (CCR). In this study, 2,3-butanediol-producing Enterobacter aerogenes was engineered to alleviate CCR and improve sugar utilization by modulating its carbon preference. Results: The gene encoding catabolite repressor/activator (Cra) was deleted in the genome of E. aerogenes to increase the fructose consumption rate. However, the deletion mutation repressed sucrose utilization, resulting in the accumulation of sucrose in the fermentation medium. Cra regulation on expression of the scrAB operon involved in sucrose catabolism was verified by reverse transcription and real-time PCR, and the efficiency of sucrose utilization was restored by disrupting the scrR gene and overexpressing the scrAB operon. In addition, overexpression of the ptsG gene involved in glucose utilization enhanced the glucose preference among mixed sugars, which relieved glucose accumulation in fed-batch fermentation. In fed-batch fermentation using sugarcane molasses, the maximum titer of 2,3-butanediol production by the mutant reached 140.0 g/L at 54 h, which was by far the highest titer of 2,3-butanediol with E. aerogenes achieved through genetic engineering. Conclusions: We have developed genetically engineered E. aerogenes as a 2,3-butanediol producer that efficiently utilizes sugarcane molasses. The fermentation efficiency was dramatically improved by the alleviation of CCR and modulation of carbon preference. These results offer a metabolic engineering approach for achieving highly efficient utilization of mixed sugars for the biorefinery industry.
KW - 2,3-Butanediol
KW - Carbon catabolite repression
KW - Catabolite repressor/activator
KW - Enterobacter aerogenes
KW - Fed-batch fermentation
KW - Sugarcane molasses
UR - http://www.scopus.com/inward/record.url?scp=84938352131&partnerID=8YFLogxK
U2 - 10.1186/s13068-015-0290-3
DO - 10.1186/s13068-015-0290-3
M3 - Article
AN - SCOPUS:84938352131
VL - 8
JO - Biotechnology for Biofuels
JF - Biotechnology for Biofuels
SN - 1754-6834
IS - 1
M1 - 106
ER -
