Investigating Acid Stress Response in Different<i>Saccharomyces</i>Strains

Brandão, Rogélio Lopes; Rosa, Júlio César Câmara; Nicoli, Jacques Robert; Almeida, Marcos Vinicius Simi; Carmo, Ana Paula do; Queiros, Heloa Teixeira; Castro, Ieso de Miranda

doi:10.1155/2014/178274

Cited by 21 publications

(20 citation statements)

References 47 publications

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“…These orthologous proteins have been associated with various physiological functions. ScCrz1p participates in the acidic and alkaline pH response through regulation of intracellular Ca 2ϩ (21,22) and, in Na ϩ /Li ϩ hypertonic saline stress, by increasing the activity of the Na ϩ /Li ϩ -ATPase proton pump (19). Overexpression of ScCrz1p was shown to increase the fermentative capacity of industrial strains (38).…”

Section: Discussionmentioning

confidence: 99%

“…In Saccharomyces cerevisiae, Crz1p (ScCrz1p) is involved in metal ion resistance (19), cell wall biogenesis (20), regulation of the transcriptional response to alkaline pH (21) or acid stress (22), and tolerance to ethanol (23). In Candida albicans, Crz1p (CaCrz1p) is implicated in antifungal susceptibility (24), virulence, lithium ion resistance, filamentation, and the regulation of pH homeostasis under alkaline and acidic conditions (24,25).…”

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confidence: 99%

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Crz1p Regulates pH Homeostasis in Candida glabrata by Altering Membrane Lipid Composition

Yan

Lin

et al. 2016

Appl Environ Microbiol

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The asexual facultative aerobic haploid yeast Candida glabrata is widely used in the industrial production of various organic acids. To elucidate the physiological function of the C. glabrata transcription factor Crz1p (CgCrz1p) and its role in tolerance to acid stress, we deleted or overexpressed the corresponding gene, CgCRZ1. Deletion of CgCRZ1 resulted in a 60% decrease in the dry weight of cells (DCW) and a 50% drop in cell viability compared with those of the wild type at pH 2.0. Expression of lipid metabolism-associated genes was also significantly downregulated. Consequently, the proportion of C 18:1 fatty acids, the ratio of unsaturated to saturated fatty acids, and the ergosterol content decreased by 30%, 46%, and 30%, respectively. Additionally, membrane integrity, fluidity, and H ؉ -ATPase activity were reduced by 45%, 9%, and 50%, respectively. In contrast, overexpression of CgCrz1p increased C 18:1 and ergosterol contents by 16% and 40%, respectively. Overexpression also enhanced membrane integrity, fluidity, and H ؉ -ATPase activity by 31%, 6%, and 20%, respectively. Moreover, in the absence of pH buffering, the DCW and pyruvate titers increased by 48% and 60%, respectively, compared to that of the wild type. Together, these results suggest that CgCrz1p regulates tolerance to acidic conditions by altering membrane lipid composition in C. glabrata. IMPORTANCEThis study provides insight into the metabolism of Candida glabrata under acidic conditions, such as those encountered during the industrial production of organic acids. We found that overexpression of the transcription factor CgCrz1p improved viability, biomass, and pyruvate yields at a low pH. Analysis of plasma membrane lipid composition indicated that CgCrz1p might play an important role in its integrity and fluidity and that it enhanced the pumping of protons in acidic environments. We propose that altering the structure of the cell membrane may provide a successful strategy for increasing C. glabrata productivity at a low pH.T he asexual facultative aerobic haploid yeast Candida glabrata is the only microorganism used for the industrial production of pyruvic (1), fumaric (2), malic (3), and ␣-ketoglutaric (4) acids. However, the accumulation of extracellular acid causes a significant reduction in the pH of the fermentation broth, thereby inhibiting cell growth and decreasing the synthesis of the target compound (5). To maintain the culture medium at a suitable pH, alkaline reagents, such as NaOH, Na 2 CO 3 , and CaCO 3 , are added, although this can result in increased osmotic stress (6). Improving the tolerance of C. glabrata to low-pH conditions should boost the economic efficiency of organic acid production. Various approaches have been attempted in this sense, including the addition of exogenous auxiliary energy substrates (7), chemical mutagenesis of microorganisms (8), rational genetic engineering (9), and adaptive evolution (10). Such approaches have achieved improvements in the titer and yield of some target organic acids ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Crz1p Regulates pH Homeostasis in Candida glabrata by Altering Membrane Lipid Composition

Yan

Lin

et al. 2016

Appl Environ Microbiol

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“…Fungal resistance or adaptation to weak organic acids rely on several mechanisms. In S. cerevisiae and other fungi, it includes maintenance of the cell wall structure, changes in plasma membrane or cell wall composition, metal metabolism, and activation of ATP-consuming membrane transporters to remove protons and anions [ 126 ]. Ullah et al [ 127 ] showed that S. cerevisiae adaptation to sorbic or acetic acid resulted in a decreased diffusional entry of the molecule.…”

Section: Prevention and Control Of Fungal Spoilage In Dairy Producmentioning

confidence: 99%

Diversity and Control of Spoilage Fungi in Dairy Products: An Update

2017

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Fungi are common contaminants of dairy products, which provide a favorable niche for their growth. They are responsible for visible or non-visible defects, such as off-odor and -flavor, and lead to significant food waste and losses as well as important economic losses. Control of fungal spoilage is a major concern for industrials and scientists that are looking for efficient solutions to prevent and/or limit fungal spoilage in dairy products. Several traditional methods also called traditional hurdle technologies are implemented and combined to prevent and control such contaminations. Prevention methods include good manufacturing and hygiene practices, air filtration, and decontamination systems, while control methods include inactivation treatments, temperature control, and modified atmosphere packaging. However, despite technology advances in existing preservation methods, fungal spoilage is still an issue for dairy manufacturers and in recent years, new (bio) preservation technologies are being developed such as the use of bioprotective cultures. This review summarizes our current knowledge on the diversity of spoilage fungi in dairy products and the traditional and (potentially) new hurdle technologies to control their occurrence in dairy foods.

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“…At the end of fermentation, the pH of the culture had dropped to 3.8, indicating a highly acidic culture environment due to the presence of acetic acid (~3 g/L). A low pH environment is known to cause acid stress in yeasts, resulting in reduced membrane permeability, anion extrusion, and alters expression of genes that are key for yeast growth [29,30].…”

Section: Batch Bioreactor Fermentations Using Semi-defined Mediamentioning

confidence: 99%

Optimised Production and Extraction of Astaxanthin from the Yeast Xanthophyllomyces dendrorhous

et al. 2020

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Currently, astaxanthin demand is fulfilled by chemical synthesis using petroleum-based feedstocks. As such, alternative pathways of natural astaxanthin production attracts much research interest. This study aimed at optimising bioreactor operation parameters for astaxanthin production and evaluating strategies for its subsequent extraction. The effect of pH and agitation was evident, as a significant reduction in both biomass and astaxanthin production was observed when the culture pH was not controlled and a low agitation speed was applied. At controlled pH conditions and a high agitation speed, a significant increase in biomass (16.4 g/L) and astaxanthin production (3.6 mg/L) was obtained. Enzymatic yeast cell lysis using two commercial enzymes (Accellerase 1500 and Glucanex) was optimised using the central composite design of experiment (DoE). Accellerase 1500 led to mild cell disruption and only 9% (w/w) astaxanthin extraction. However, Glucanex treatment resulted in complete astaxanthin extractability, compared to standard extraction method (DMSO/acetone). When supercritical CO 2 was employed as an extraction solvent in Accellerase-pre-treated Xanthophyllomyces dendrorhous cells, astaxanthin extraction increased 2.5-fold. Overall, the study showed that extraction conditions can be tailored towards targeted pigments present in complex mixtures, such as in microbial cells.Microorganisms 2020, 8, 430 2 of 18 up and commercialisation of astaxanthin production [3-5], while its extraction and purification still contributes to the overall complexity and cost of the whole production process.Various cultivation modes, including batch, fed-batch, and continuous, have been investigated for carotenoid production in yeasts, either in the lab or at the pilot scale [6][7][8]. In the case of some yeast species cultivated on batch mode, high initial carbon concentrations (usually glucose) result in suppression of cell growth as well as product formation due to the Crabtree effect [9,10]. It has been demonstrated that X. dendrorhous undergoes the Crabtree effect, a phenomenon where cells metabolically switch to fermentative metabolism leading to ethanol production even under ample oxygen supply when initial glucose present is above a given threshold (strain dependent) [10,11]. Fed-batch cultivation mode is considered as an appropriate strategy to overcome such issues, as it allows the addition of one or more nutrients to the reactor during fermentation in order to maintain the concentration of the substrate below its inhibitory levels [12]. Furthermore, with regards to media optimization, low concentrations of ammonium and phosphate have been reported to be favourable towards astaxanthin production, whereas increased levels of citrate in the growth medium have been shown to stimulate astaxanthin production, as citrate can act as a carbon source towards astaxanthin biosynthesis in Phaffia rhodozyma [13]. The effect of light on astaxanthin productivity in several yeast and microalgae strains has been also extensively studied [1...

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Investigating Acid Stress Response in DifferentSaccharomycesStrains

Cited by 21 publications

References 47 publications

Crz1p Regulates pH Homeostasis in Candida glabrata by Altering Membrane Lipid Composition

Crz1p Regulates pH Homeostasis in Candida glabrata by Altering Membrane Lipid Composition

Diversity and Control of Spoilage Fungi in Dairy Products: An Update

Optimised Production and Extraction of Astaxanthin from the Yeast Xanthophyllomyces dendrorhous

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