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3 results on '"Signori L"'

1. Different response to acetic acid stress in Saccharomyces cerevisiae wild-type and l-ascorbic acid-producing strains.

Author

Martani F, Fossati T, Posteri R, Signori L, Porro D, and Branduardi P

Subjects
Catalase metabolism, Metabolic Engineering, Reactive Oxygen Species metabolism, Saccharomyces cerevisiae metabolism, Superoxide Dismutase metabolism, Acetic Acid toxicity, Ascorbic Acid metabolism, Drug Tolerance, Saccharomyces cerevisiae drug effects, Saccharomyces cerevisiae physiology, Stress, Physiological
Abstract

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 pretreatment 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 concentrations, measured as viability on plates. Starting from this evidence, we investigated more deeply: (a) the nature and levels of reactive oxygen species (ROS); (b) the activation of enzymes that act directly as detoxifiers of reactive oxygen species, 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 acid damage; moreover, these studies will possibly provide additional targets for further strain improvements., (Copyright © 2013 John Wiley & Sons, Ltd.)

Published
2013
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2. Assessing physio-macromolecular effects of lactic acid on Zygosaccharomyces bailii cells during microaerobic fermentation

Author

Paola Branduardi, Diletta Ami, John P. Morrissey, Lorenzo Signori, Nurzhan Kuanyshev, Danilo Porro, Kuanyshev, N, Ami, D, Signori, L, Porro, D, Morrissey, J, and Branduardi, P

Subjects
0301 basic medicine, Chemical Phenomena, Protein Conformation, Zygosaccharomyces bailii, Saccharomyces cerevisiae, Bioreactor, Zygosaccharomyces, Microbiology, Applied Microbiology and Biotechnology, Cell wall, Fungal Proteins, 03 medical and health sciences, chemistry.chemical_compound, Bioreactors, Cell Wall, Stress, Physiological, Spectroscopy, Fourier Transform Infrared, Propidium iodide, Anaerobiosis, Lactic Acid, Microbial Viability, biology, Staining and Labeling, Medicine (all), Cell Membrane, food and beverages, General Medicine, Hydrogen-Ion Concentration, biology.organism_classification, CHIM/11 - CHIMICA E BIOTECNOLOGIA DELLE FERMENTAZIONI, Yeast, Lactic acid, Culture Media, 030104 developmental biology, chemistry, Biochemistry, FTIR, Fermentation, Propidium
Abstract

The ability of Zygosaccharomyces bailii to grow at low pH and in the presence of considerable amounts of weak organic acids, at lethal condition for Saccharomyces cerevisiae , increased the interest in the biotechnological potential of the yeast. To understand the mechanism of tolerance and growth effect of weak acids on Z. bailii , we evaluated the physiological and macromolecular changes of the yeast exposed to sub lethal concentrations of lactic acid. Lactic acid represents one of the important commodity chemical which can be produced by microbial fermentation. We assessed physiological effect of lactic acid by bioreactor fermentation using synthetic media at low pH in the presence of lactic acid. Samples collected from bioreactors were stained with propidium iodide (PI) which revealed that, despite lactic acid negatively influence the growth rate, the number of PI positive cells is similar to that of the control. Moreover, we have performed Fourier Transform Infra-Red (FTIR) microspectroscopy analysis on intact cells of the same samples. This technique has been never applied before to study Z. bailii under this condition. The analyses revealed lactic acid induced macromolecular changes in the overall cellular protein secondary structures, and alterations of cell wall and membrane physico-chemical properties.

Published
2016

3. Re-assessment of YAP1 and MCR1 contributions to inhibitor tolerance in robust engineered Saccharomyces cerevisiae fermenting undetoxified lignocellulosic hydrolysate

Author

Maria R. Foulquié-Moreno, Maurizio Bettiga, Yingying Li, Paola Branduardi, Magnus Ask, Valeria Wallace-Salinas, Lorenzo Signori, Marie-Francoise Gorwa-Grauslund, Danilo Porro, Johan M. Thevelein, Wallace Salinas, V, Signori, L, Li, Y, Ask, M, Bettiga, M, Porro, D, Thevelein, J, Branduardi, P, Foulquié Moreno, M, and Gorwa Grauslund, M

Subjects
2. Zero hunger, YAP1, Inhibitor, biology, Ethanol, Catabolism, Inhibitors, Saccharomyces cerevisiae, Biophysics, MCR1, Reductase, Xylose, biology.organism_classification, CHIM/11 - CHIMICA E BIOTECNOLOGIA DELLE FERMENTAZIONI, Applied Microbiology and Biotechnology, Hydrolysate, Yeast, chemistry.chemical_compound, chemistry, Biochemistry, Fermentation, Original Article
Abstract

Development of robust yeast strains that can efficiently ferment lignocellulose-based feedstocks is one of the requirements for achieving economically feasible bioethanol production processes. With this goal, several genes have been identified as promising candidates to confer improved tolerance to S. cerevisiae. In most of the cases, however, the evaluation of the genetic modification was performed only in laboratory strains, that is, in strains that are known to be quite sensitive to various types of stresses. In the present study, we evaluated the effects of overexpressing genes encoding the transcription factor (YAP1) and the mitochondrial NADH-cytochrome b5 reductase (MCR1), either alone or in combination, in an already robust and xylose-consuming industrial strain of S. cerevisiae and evaluated the effect during the fermentation of undiluted and undetoxified spruce hydrolysate. Overexpression of either gene resulted in faster hexose catabolism, but no cumulative effect was observed with the simultaneous overexpression. The improved phenotype of MCR1 overexpression appeared to be related, at least in part, to a faster furaldehyde reduction capacity, indicating that this reductase may have a wider substrate range than previously reported. Unexpectedly a decreased xylose fermentation rate was also observed in YAP1 overexpressing strains and possible reasons behind this phenotype are discussed.

Published
2014

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