Abstract
In-depth knowledge of cell metabolism and nutrient uptake mechanisms can lead to the development of a tool for improving acetone-butanol-ethanol (ABE) fermentation performance and help to overcome bottlenecks in the process, such as the high cost of substrates and low production rates. Over 300 genes potentially encoding transport of amino acids, metal ions, vitamins and carbohydrates were identified in the genome of the butanol-producing strain Clostridium beijerinckii NRRL B-598, based on similarity searches in protein function databases. Transcriptomic data of the genes were obtained during ABE fermentation by RNA-Seq experiments and covered acidogenesis, solventogenesis and sporulation. The physiological roles of the selected 81 actively expressed transport genes were established on the basis of their expression profiles at particular stages of ABE fermentation. This article describes how genes encoding the uptake of glucose, iron, riboflavin, glutamine, methionine and other nutrients take part in growth, production and stress responses of C. beijerinckii NRRL B-598. These data increase our knowledge of transport mechanisms in solventogenic Clostridium and may be used in the selection of individual genes for further research.
Highlights
Until the 1950s, ABE fermentation by clostridial species was one of the largest industrial biotechnological processes, the second largest after ethanol fermentation
We identify genes encoding putative transporters of amino acids, metal ions, vitamins and carbohydrates in C. beijerinckii NRRL B-598, combined with their transcriptomic data obtained from the whole life cycle of the bacterium, including acidogenesis, solventogenesis and sporulation
The experiments comprised two-phase ABE fermentation: the acidogenic phase, which is characterized by acid production and pH decrease, and the solventogenic phase, when glucose and organic acids are utilized to produce solvents
Summary
Until the 1950s, ABE fermentation by clostridial species was one of the largest industrial biotechnological processes, the second largest after ethanol fermentation. It became unprofitable after the development of petrochemical methods for solvent production, methods which have been used exclusively until now. Due to environmental concerns and resource limitations there is a demand for renewable methods of fuel and chemical production, independent of crude-oil [1]; ABE fermentation as an alternative and ecological process is being reinvestigated [2]. The major products of ABE fermentation are butanol, acetone and ethanol, which in the well-studied solventogenic strain Clostridium acetobutylicum ATCC 824, are usually produced.
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