Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms
2015
Cray, Jonathan A | Stevenson, Andrew | Ball, Philip | Bankar, Sandip B | Eleutherio, Elis CA | Ezeji, Thaddeus C. | Singhal, Rekha S. | Thevelein, Johan M | Timson, David J. | Hallsworth, John E
Fermentation products can chaotropically disorder macromolecular systems and induce oxidative stress, thus inhibiting biofuel production. Recently, the chaotropic activities of ethanol, butanol and vanillin have been quantified (5.93, 37.4, 174kJkg−1m−1 respectively). Use of low temperatures and/or stabilizing (kosmotropic) substances, and other approaches, can reduce, neutralize or circumvent product-chaotropicity. However, there may be limits to the alcohol concentrations that cells can tolerate; e.g. for ethanol tolerance in the most robust Saccharomyces cerevisiae strains, these are close to both the solubility limit (<25%, w/v ethanol) and the water-activity limit of the most xerotolerant strains (0.880). Nevertheless, knowledge-based strategies to mitigate or neutralize chaotropicity could lead to major improvements in rates of product formation and yields, and also therefore in the economics of biofuel production.
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