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Biotechnological processes are of increasing significance for industrial production of fine and bulk chemicals, including biofuels. Unfortunately, under operative conditions microorganisms meet multiple stresses such as non-optimal pH, temperature, oxygenation and osmotic stress. Moreover, they have to face inhibitory compounds released during the pre-treatment of lignocellulosic biomasses, which constitute the preferential substrate for second generation processes. Inhibitors include furan derivatives, phenolic compounds and weak organic acids, among which acetic acid is one of the most abundant and detrimental for cells. They impair cellular metabolism and growth, reducing the productivity of the process: therefore, the development of robust cell factories with improved production rates and resistance is of crucial importance. Here we show that a yeast strain engineered to endogenously produce vitamin C exhibits an increased tolerance compared to the parental strain when exposed to acetic acid at moderately-toxic concentration, measured as viability on plates. Starting from this evidence we deeper investigated i) the nature and levels of reactive oxygen species ii) the activation of enzymes that act directly as detoxifiers of reactive oxygen species (ROS), such as superoxide dismutase (SOD) and catalase in parental and engineered strains during acetic acid stress. The data indicate that the engineered strain can better recover from stress by limiting ROS accumulation, independently from SOD activation. The engineered yeast can be proposed as a model for further investigating direct and indirect mechanism(s) by which an antioxidant can rescue cells from organic acids damages; moreover, said studies will possibly provide additional targets for further strain improvements. This article is protected by copyright. All rights reserved.
PMID: 23847041 [PubMed - as supplied by publisher]