Mechanisms of weak acid-induced stress tolerance in yeasts: Prospects for improved bioethanol production from lignocellulosic biomass |
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Institution: | 1. Material Resource Efficiency Division (MRED), CSIR-Indian Institute of Petroleum, Mohkampur, Haridwar Road, Dehradun 248005, Uttarakhand, India;2. Academy of Scientific and Innovative Research (AcSIR), CSIR-HRDC Campus, Ghaziabad 210002, India;3. Department of Biosciences and Bioengineering, Indian Institute of Technology-Roorkee, Roorkee, Uttarakhand-247667 |
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Abstract: | Weak acids are known to have a negative impact on yeast performance, restraining production efficiency during the production of bioethanol and other fermentative yeast-derived products. These acids, which might be hydrophilic or lipophilic exert negative effects on yeasts when they diffuse into the cell in their unionized state as a result of their pH being lower than the pka of yeast growth medium. Consequently, the unionized acids dissociate into their respective cations and anions, as intracellular pH is typically neutral. Further, proton accumulation tends to reduce intracellular pH. As a result, the anions destabilize the internal cell machinery, thus affecting cellular metabolism on various levels. Overcoming this acid-mediated stress in budding yeast would in part, harness the potential of using lignocellulosic biomass hydrolysate – which is typically acetic acid-rich – as a cheaper feedstock for large-scale bioethanol production. Since organic acids are key intermediates in ethanol fermentation, this review focuses on the prospects of bioethanol production from lignocellulosic biomass using weak acid-tolerant strains of yeasts derived by metabolic engineering. |
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Keywords: | Acetic acid Weak acid tolerance Yeasts Bioethanol Ligcocellulosic hydrolysate Fermentation |
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