Genomic, Transcriptional, and Phenotypic Analysis of the Glucose Derepressed Clostridium beijerinckii Mutant Exhibiting Acid Crash Phenotype

• Published in: Biotechnology journal 2017-11, Vol.12 (11), p.n/a
• Main Authors: Seo, Seung‐Oh, Janssen, Holger, Magis, Andrew, Wang, Yi, Lu, Ting, Price, Nathan D., Jin, Yong‐Su, Blaschek, Hans P.
• Format: Article
• Language: English
• Subjects: Acetone - metabolism; Alcohols - metabolism; Clostridium beijerinckii - genetics; Clostridium beijerinckii - metabolism; Fermentation; Gene Expression Profiling; Genome, Bacterial - genetics; Genomics; Glucose - metabolism; Hydrogen-Ion Concentration; Mutation - genetics; Mutation - physiology; Phenotype; Polymorphism, Single Nucleotide - genetics
• ISSN: 1860-6768; 1860-7314
• DOI: 10.1002/biot.201700182

Clostridium beijerinckii is a predominant solventogenic bacterium that is used for the ABE fermentation. Various C. beijerinckii mutants are constructed for desirable phenotypes. The C. beijerinckii mutant BA105 harboring a glucose derepression phenotype was previously isolated and demonstrated the enhanced amylolytic activity in the presence of glucose. Despite its potential use, BA105 is not further characterized and utilized. Therefore, the authors investigate fermentation phenotypes of BA105 in this study. Under the typical batch fermentation conditions, BA105 consistently exhibits acid crash phenotype resulting in limited glucose uptake and cell growth. However, when the culture pH is maintained above 5.5, BA105 exhibits the increased glucose uptake and butanol production than did the wild‐type. To further analyze BA105, the authors perform genome sequencing and RNA sequencing. Genome analysis identifies two SNPs unique to BA105, in the upstream region of AbrB regulator (Cbei_4885) and the ROK family glucokinase (Cbei_4895) which are involved in catabolite repression and regulation of sugar metabolism. Transcriptional analysis of BA105 reveals significant differential expression of the genes associated with the PTS sugar transport system and acid production. This study improves understanding of the acid crash phenomenon and provides the genetic basis underlying the catabolite derepression phenotype of C. beijericnkii. This study reveals that the glucose derepressed Clostridium beijerinckii mutant BA105 containing genetic mutations exhibits the fast glucose metabolism and acid overproduction, resulting in the acid crash in the absence of the pH control. When the pH is controlled at 5.5, the acid crash phenotype of BA105 became advantageous for production of solvents that are converted from the acids. The pH control could alleviate the acid toxicity by decreasing the abundance ratio of the undissociated acid form which is toxic to the cell. The BA105 is further analyzed in this study to identify the possible reasons for the phenotypic changes when compared to the wild‐type.