Abstract
Background2,3-Butanediol (2,3-BD) is a high-value chemical usually produced petrochemically but which can also be synthesized by some bacteria. To date, Klebsiella pneumoniae is the most powerful 2,3-BD producer which can utilize a wide range of substrates. However, many by-products are also produced by K. pneumoniae, such as ethanol, lactate, and acetate, which negatively regulate the 2,3-BD yield and increase the costs of downstream separation and purification.ResultsIn this study, we constructed K. pneumoniae mutants with lactate dehydrogenase (LDH), acetaldehyde dehydrogenase (ADH), and phosphotransacetylase (PTA) deletion individually by suicide vector conjugation.These mutants showed different behavior of production formation. Knock out of ldhA had little influence on the yield of 2,3-BD, whereas knock out of adhE or pta significantly improved the formation of 2,3-BD. The accumulation of the intermediate of 2,3-BD biosynthesis, acetoin, was decreased in all the mutants. The mutants were then tested in five different carbon sources and increased 2,3-BD was observed. Also a double mutant strain with deletion of adhE and ldhA was constructed which resulted in accelerated fermentation and higher 2,3-BD production. In fed-batch culture this strain achieved more than 100 g/L 2,3-BD from glucose with a relatively high yield of 0.49 g/g.Conclusion2,3-BD production was dramatically improved with the inactivation of adhE and pta. The inactivation of ldhA could advance faster cell growth and shorter fermentation time. The double mutant strain with deletion of adhE and ldhA resulted in accelerated fermentation and higher 2,3-BD production. These results provide new insights for industrial production of 2,3-BD by K. pneumoniae.
Highlights
Biorefineries for chemicals have attracted a great deal of interest because they can alleviate the dependence on oil supply for the production of platform chemicals, reduce environmental pollution, and ensure sustainable development [1,2]
lactate dehydrogenase (LDH), acetaldehyde dehydrogenase (ADH), and PTA activity assays The activities of LDH, ADH, and PTA in the mutants and parent strain were determined
The engineering strategy pursued in this study, which was based on the redirection of carbons toward the production of byproducts, led to the development of K. pneumoniae strains with high efficiency for 2,3-BD production
Summary
Biorefineries for chemicals have attracted a great deal of interest because they can alleviate the dependence on oil supply for the production of platform chemicals, reduce environmental pollution, and ensure sustainable development [1,2]. The inactivation of acetaldehyde dehydrogenase gene significantly increases the 2,3-BD yield and decreases ethanol production [11]. Deletion of the ldh gene encodes lactate dehydrogenase (LDH) in E. aerogenes, resulting in a very small amount of lactate yield and 16.7% more 2,3-BD than that of the parent strain in batch fermentation [9]. The ldh, ldhB, and ldhX genes in Lactococcus lactis, which encode LDH, have been deleted, and the results showed that ΔldhB is a valuable basis for engineering strategies for the production of reduced compounds [15]. The deletion of adhE in K. oxytoca increases the hydrogen yield of the mutant by 16.07% but decreases the ethanol concentration by 77.47%, compared with those of the parent strain [16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
