Application of response surface methodology in medium optimization for pyruvic acid production of Torulopsis glabrata TP19 in batch fermentation

Zhang, Jian; Nian-fa, Gao

doi:10.1631/jzus.2007.b0098

Cited by 28 publications

(8 citation statements)

References 28 publications

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“…Nevertheless, such approaches have some serious drawbacks, such as a heavy workload, uncertainty, and growth defects (23,(29)(30)(31). Here, we propose a strategy that could overcome the above-mentioned problems by enhancing pyruvate production through overexpression of Med15B and increased dry weight of cells.…”

Section: Discussionmentioning

confidence: 99%

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Liu

et al. 2017

Appl Environ Microbiol

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Candida glabrata is a promising producer of organic acids. To elucidate the physiological function of the Mediator tail subunit Med15B in the response to low-pH stress, we constructed a deletion strain, C. glabrata med15BΔ, and an overexpression strain, C. glabrata HTUΔ/CgMED15B. Deletion of MED15B caused biomass production, glucose consumption rate, and cell viability to decrease by 28.3%, 31.7%, and 26.5%, respectively, compared with those of the parent (HTUΔ) strain at pH 2.0. Expression of lipid metabolism-related genes was significantly downregulated in the med15BΔ strain, whereas key genes of ergosterol biosynthesis showed abnormal upregulation. This caused the proportion of C 18:1 fatty acids, the ratio of unsaturated to saturated fatty acids (UFA/SFA), and the total phospholipid content to decrease by 11.6%, 27.4%, and 37.6%, respectively. Cells failed to synthesize fecosterol and ergosterol, leading to the accumulation and a 60.3-fold increase in the concentration of zymosterol. Additionally, cells showed reductions of 69.2%, 11.6%, and 21.8% in membrane integrity, fluidity, and H ϩ -ATPase activity, respectively. In contrast, overexpression of Med15B increased the C 18:1 levels, total phospholipids, ergosterol content, and UFA/SFA by 18.6%, 143.5%, 94.5%, and 18.7%, respectively. Membrane integrity, fluidity, and H ϩ -ATPase activity also increased by 30.2%, 6.9%, and 51.8%, respectively. Furthermore, in the absence of pH buffering, dry weight of cells and pyruvate concentrations were 29.3% and 61.2% higher, respectively, than those of the parent strain. These results indicated that in C. glabrata, Med15B regulates tolerance toward low pH via transcriptional regulation of acid stress response genes and alteration in lipid composition. IMPORTANCE This study explored the role of the Mediator tail subunit Med15B in the metabolism of Candida glabrata under acidic conditions. Overexpression of MED15B enhanced yeast tolerance to low pH and improved biomass production, cell viability, and pyruvate yield. Membrane lipid composition data indicated that Med15B might play a critical role in membrane integrity, fluidity, and H ϩ -ATPase activity homeostasis at low pH. Thus, controlling membrane composition may serve to increase C. glabrata productivity at low pH.KEYWORDS Candida glabrata, Mediator subunit Med15B, low-pH stress, transcriptomics, membrane lipid T he Mediator coactivator complex is required for transcription initiation in eukaryotes (1, 2). It is recruited by transcription activators and conveys regulatory information from gene-specific regulators to promoters (3, 4). Mediator can influence almost all stages of transcription and coordinated processes such as chromatin remodeling, transcription elongation, and posttranslational modifications (5, 6). Mediator is a multisubunit assembly comprising four modules: head, middle, tail, and cyclin-dependent kinase 8 (CDK8) (7). The head and middle modules are highly

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Section: Discussionmentioning

confidence: 99%

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Liu

et al. 2017

Appl Environ Microbiol

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“…One of the important inputs of RSM is representation of the yield, as a surface plot. It can provide multiple responses at the same time by considering the interactions between the variables, which is utmost necessary for designing and process optimization (Zhang and Gao, 2007). Since, the theoretical relationships between the independent and dependent variables are not clear, multiple regression analysis can be applied to predict the dependent variables on the basis of a second-order equation.…”

Section: Media Optimization Strategiesmentioning

confidence: 99%

Strategies for Fermentation Medium Optimization: An In-Depth Review

et al. 2017

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Optimization of production medium is required to maximize the metabolite yield. This can be achieved by using a wide range of techniques from classical “one-factor-at-a-time” to modern statistical and mathematical techniques, viz. artificial neural network (ANN), genetic algorithm (GA) etc. Every technique comes with its own advantages and disadvantages, and despite drawbacks some techniques are applied to obtain best results. Use of various optimization techniques in combination also provides the desirable results. In this article an attempt has been made to review the currently used media optimization techniques applied during fermentation process of metabolite production. Comparative analysis of the merits and demerits of various conventional as well as modern optimization techniques have been done and logical selection basis for the designing of fermentation medium has been given in the present review. Overall, this review will provide the rationale for the selection of suitable optimization technique for media designing employed during the fermentation process of metabolite production.

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“…The combined extract was then washed with 20 ml of brine solution twice, dried over anhydrous sodium sulphate and evaporated to get the residue. The product formation was confirmed by TLC using ethyl acetate: hexane: acetic acid (5:4:1) solvent system (Zhang J. et al, 2007). The product was quantified by HPLC analysis.…”

Section: Bioreduction With Baker's Yeast Aspergillus Tubingenesismentioning

confidence: 99%

Biocatalytic Ketone Reduction - A Study on Screening and Effect of Culture Conditions on the Reduction of Selected Ketones

Kuncham¹,

Gurumurthy²,

Chandan³

et al. 2013

ILNS

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Microbial conversions are gaining importance in the synthesis of important drug metabolites and their intermediates as they are good alternative to chemical synthesis since they are enantioselective and regio-selective and even can be carried out at ambient temperature and atmospheric pressure. Till date, biocatalytic reduction of acetophenone and its derivatives has been widely reported. In the present study, we have made an attempt to carry out the microbial bioreduction of ohydroxyacetophenone by screening some of the selected microorganisms which were obtained from culture collection centre as well as those which are isolated in our Microbiology lab. The selected microorganisms include Aspergillus ochraceous, Aspergillus flavus, Aspergillus tubingenesis, Aspergillus niger, Rhizopus stolanifer MTCC 162, Rhizopus stolanifer MTCC 2591 and Baker's yeast.Among the seven microorganisms screened for the bioreduction of o-hydroxyacetophenone, Baker's yeast and Aspergillus tubingenesis showed significant bioconversion where as Aspergillus ochraceous exhibited the least bioconversion.In our earlier study it was found that Aspergillus flavus has the required bioreductase enzyme, which showed the maximum conversion of pchloroacetophenone to p-chlorophenylethanol. Hence optimization of culture conditions to get maximum enzyme expression and hence maximum conversion was thought off. The parameters considered for the study include effect of various Carbon sources, Nitrogen source, Metal ions, incubation Temperature and media pH on enzyme expression. The optimized culture a condition at which maximum bioconversion was achieved was maltose among various carbon sources. Tryptone was found to have maximum effect among the nitrogen sources. Media pH 7.6 and incubation temperature of 35 °C was found to be favourable for maximum enzyme activity. Among various divalent metal salts, addition of magnesium sulphate to the media significantly increased the enzyme activity.

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Application of response surface methodology in medium optimization for pyruvic acid production of Torulopsis glabrata TP19 in batch fermentation

Cited by 28 publications

References 28 publications

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Strategies for Fermentation Medium Optimization: An In-Depth Review

Biocatalytic Ketone Reduction - A Study on Screening and Effect of Culture Conditions on the Reduction of Selected Ketones

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