The recombinant strain thus created was used in a growth-arrested process where product production phase and cell catalyst production phase are uncoupled. Growth-cessation is achieved simply by the lowering of the oxygen tension which results when a high density cell suspension is incubated in the absence of aeration. The main metabolic machinery remains however functional and the production reaction can be continued for several weeks using the same growth-arrested cells. An important property of this design is that the bulk of the carbon source is directed towards product production rather than towards vegetative functions. Ethanol productivities greater than 30 g/l/h could be routinely attained 1).
This work paves the way for the construction of an efficient bioconverter strain capable of cost-effectively utilising various sugars, and particularly the pentose sugars that are typically contained in saccharified lignocellulosic mixtures. Notably, the fast on/off response displayed by the process/converter strain system that we propose facilitates the implementation of continuous ethanol fermentation production that can be run at steady-state for an extended period of time. This property is critical for the realization of the biorefinery concept.
This study was partially supported by a grant from New Energy and Industrial Technology Development Organization (NEDO).
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