Ethanol Tolerance and Titer

For ethanol, or any other fermentation product, there are limiting concentrations at which metabolic functions cease to be operative. Because the limiting concentration for catabolism is often greater than for anabolism, it is possible - and 

On the basis of these considerations, the feasible window for stand-alone facilities processing lignocellulose to ethanol is bounded on the low side by distillation energy requirements and on the high side by the difficulty of handling biomass 

Notwithstanding recent progress, it remains to be demonstrated that ther-mophiles can produce economically viable titers under industrial conditions - for example, an affordable lignocellulosic feedstock, inexpensive growth media, and in the presence of potential inhibitors. It has been shown that thermophiles can be adapted to manifest increased resistance to inhibitors other than ethanol, in particular in the case of by-products resulting from Populus pretreatment [85]. We speculate that it may be difficult and perhaps not feasible to develop strains of thermophiles that are as resistant to chemical inhibition as yeast, and that the merits of thermophiles may be best realized in the context of processes that minimize formation of inhibitors in the first place. 

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