(609h) Genomic and Proteomic Analysis to Characterize Butyric Acid Fermentation By Metabolically Engineered Clostridium Tyrobutyricum

The production of butyric acid, widely used in chemical, food and pharmaceutical industries, via fermentation using Clostridium tyrobutyricum has drawn an increasing attention. Both wild type C. tyrobutyricum and the metabolically engineered mutant PAK-Em with down-regulated acetate kinase were used to produce butyric acid at pH 6.0 and 37 ^oC. The free-cell fermentation showed that the mutant cells produced higher production of butyric acid than wild type in terms of titer (38 g/L vs. 20 g/L) and yield (0.43 g/g vs. 0.35 g/g). However, the cell growth rate of the engineered mutant was around 30% lower than that of wild type. To understand the mechanism of butyric acid production and cell growth regulation in engineered C. tyrobutyricum mutant, the comparative genomics and proteomics studies were performed. Around 50% genome sequences were annotated and showed that multiple mutations happened in the engineered mutant, including one deletion, one insertion, five non-synonymous coding genes, three stop codons gained and one stop codon lost. It was concluded that the genome mutations in transcription, translation, amino acid and phosphate transportation and cofactor binding might play important role in regulating cell growth and butyric acid production. The intracellular protein analysis demonstrated significant changes in the expression of the genes related to primary metabolism although genome mutation was not detected in these genes. In future work, the de novo sequencing and mapping will be completed to further characterize the metabolically engineered C. tyrobutyricum mutant and identify the host cell regulators of cell growth and butyric acid production.