scholarly journals Improvement of Glucose Uptake Rate and Production of Target Chemicals by Overexpressing Hexose Transporters and Transcriptional Activator Gcr1 in Saccharomyces cerevisiae

2015 ◽  
Vol 81 (24) ◽  
pp. 8392-8401 ◽  
Author(s):  
Daehee Kim ◽  
Ji-Yoon Song ◽  
Ji-Sook Hahn
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Glucose Uptake ◽  
Uptake Rate ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Glucose Uptake Rate ◽  
Promoting Effect ◽  
Content Type ◽  
Hexose Transporters

ABSTRACTMetabolic engineering to increase the glucose uptake rate might be beneficial to improve microbial production of various fuels and chemicals. In this study, we enhanced the glucose uptake rate inSaccharomyces cerevisiaeby overexpressing hexose transporters (HXTs). Among the 5 tested HXTs (Hxt1, Hxt2, Hxt3, Hxt4, and Hxt7), overexpression of high-affinity transporter Hxt7 was the most effective in increasing the glucose uptake rate, followed by moderate-affinity transporters Hxt2 and Hxt4. Deletion ofSTD1andMTH1, encoding corepressors ofHXTgenes, exerted differential effects on the glucose uptake rate, depending on the culture conditions. In addition, improved cell growth and glucose uptake rates could be achieved by overexpression ofGCR1, which led to increased transcription levels ofHXT1and ribosomal protein genes. All genetic modifications enhancing the glucose uptake rate also increased the ethanol production rate in wild-typeS. cerevisiae. Furthermore, the growth-promoting effect ofGCR1overexpression was successfully applied to lactic acid production in an engineered lactic acid-producing strain, resulting in a significant improvement of productivity and titers of lactic acid production under acidic fermentation conditions.

scholarly journals Improvement of Lactic Acid Production in Saccharomyces cerevisiae by Cell Sorting for High Intracellular pH

2006 ◽  
Vol 72 (8) ◽  
pp. 5492-5499 ◽  
Author(s):  
Minoska Valli ◽  
Michael Sauer ◽  
Paola Branduardi ◽  
Nicole Borth ◽  
Danilo Porro ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Intracellular Ph ◽  
Cell Sorting ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Low Ph ◽  
The Mean ◽  
High Level ◽  
Lactate Dehydrogenases

ABSTRACT Yeast strains expressing heterologous l-lactate dehydrogenases can produce lactic acid. Although these microorganisms are tolerant of acidic environments, it is known that at low pH, lactic acid exerts a high level of stress on the cells. In the present study we analyzed intracellular pH (pHi) and viability by staining with cSNARF-4F and ethidium bromide, respectively, of two lactic-acid-producing strains of Saccharomyces cerevisiae, CEN.PK m850 and CEN.PK RWB876. The results showed that the strain producing more lactic acid, CEN.PK m850, has a higher pHi. During batch culture, we observed in both strains a reduction of the mean pHi and the appearance of a subpopulation of cells with low pHi. Simultaneous analysis of pHi and viability proved that the cells with low pHi were dead. Based on the observation that the better lactic-acid-producing strain had a higher pHi and that the cells with low pHi were dead, we hypothesized that we might find better lactic acid producers by screening for cells within the highest pHi range. The screening was performed on UV-mutagenized populations through three consecutive rounds of cell sorting in which only the viable cells within the highest pHi range were selected. The results showed that lactic acid production was significantly improved in the majority of the mutants obtained compared to the parental strains. The best lactic-acid-producing strain was identified within the screening of CEN.PK m850 mutants.

Lactic acid production from xylose by engineered Saccharomyces cerevisiae without PDC or ADH deletion

2015 ◽  
Vol 99 (19) ◽  
pp. 8023-8033 ◽  
Author(s):  
Timothy L. Turner ◽  
Guo-Chang Zhang ◽  
Soo Rin Kim ◽  
Vijay Subramaniam ◽  
David Steffen ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Engineered Saccharomyces Cerevisiae

d-Lactic acid production by metabolically engineered Saccharomyces cerevisiae

2006 ◽  
Vol 101 (2) ◽  
pp. 172-177 ◽  
Author(s):  
Nobuhiro Ishida ◽  
Tomiko Suzuki ◽  
Kenro Tokuhiro ◽  
Eiji Nagamori ◽  
Toru Onishi ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Engineered Saccharomyces Cerevisiae

scholarly journals Major Role of NAD-Dependent Lactate Dehydrogenases in the Production of l-Lactic Acid with High Optical Purity by the Thermophile Bacillus coagulans

2014 ◽  
Vol 80 (23) ◽  
pp. 7134-7141 ◽  
Author(s):  
Limin Wang ◽  
Yumeng Cai ◽  
Lingfeng Zhu ◽  
Honglian Guo ◽  
Bo Yu
Keyword(s):  
Lactic Acid ◽  
Lactate Dehydrogenase ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Optical Purity ◽  
Bacillus Coagulans ◽  
Lactobacillus Delbrueckii ◽  
Content Type ◽  
High Optical Purity ◽  
Optically Pure

ABSTRACTBacillus coagulans2-6 is an excellent producer of optically purel-lactic acid. However, little is known about the mechanism of synthesis of the highly optically purel-lactic acid produced by this strain. Three enzymes responsible for lactic acid production—NAD-dependentl-lactate dehydrogenase (l-nLDH; encoded byldhL), NAD-dependentd-lactate dehydrogenase (d-nLDH; encoded byldhD), and glycolate oxidase (GOX)—were systematically investigated in order to study the relationship between these enzymes and the optical purity of lactic acid.Lactobacillus delbrueckiisubsp.bulgaricusDSM 20081 (ad-lactic acid producer) andLactobacillus plantarumsubsp.plantarumDSM 20174 (adl-lactic acid producer) were also examined in this study as comparative strains, in addition toB. coagulans. The specific activities of key enzymes for lactic acid production in the three strains were characterizedin vivoandin vitro, and the levels of transcription of theldhL,ldhD, and GOX genes during fermentation were also analyzed. The catalytic activities ofl-nLDH andd-nLDH were different inl-,d-, anddl-lactic acid producers. Onlyl-nLDH activity was detected inB. coagulans2-6 under native conditions, and the level of transcription ofldhLinB. coagulans2-6 was much higher than that ofldhDor the GOX gene at all growth phases. However, for the twoLactobacillusstrains used in this study,ldhDtranscription levels were higher than those ofldhL. The high catalytic efficiency ofl-nLDH toward pyruvate and the high transcription ratios ofldhLtoldhDandldhLto the GOX gene provide the key explanations for the high optical purity ofl-lactic acid produced byB. coagulans2-6.

scholarly journals Plasticity of the Pyruvate Node Modulates Hydrogen Peroxide Production and Acid Tolerance in Multiple Oral Streptococci

2017 ◽  
Vol 84 (2) ◽  
Author(s):  
Xingqun Cheng ◽  
Sylvio Redanz ◽  
Nyssa Cullin ◽  
Xuedong Zhou ◽  
Xin Xu ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Environmental Conditions ◽  
Dental Plaque ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Acid Tolerance ◽  
Oral Bacteria ◽  
Low Ph ◽  
Content Type ◽  
Pyruvate Node

ABSTRACTCommensalStreptococcus sanguinisandStreptococcus gordoniiare pioneer oral biofilm colonizers. Characteristic for both is the SpxB-dependent production of H2O2, which is crucial for inhibiting competing biofilm members, especially the cariogenic speciesStreptococcus mutans. H2O2production is strongly affected by environmental conditions, but few mechanisms are known. Dental plaque pH is one of the key parameters dictating dental plaque ecology and ultimately oral health status. Therefore, the objective of the current study was to characterize the effects of environmental pH on H2O2production byS. sanguinisandS. gordonii.S. sanguinisH2O2production was not found to be affected by moderate changes in environmental pH, whereasS. gordoniiH2O2production declined markedly in response to lower pH. Further investigation into the pyruvate node, the central metabolic switch modulating H2O2or lactic acid production, revealed increased lactic acid levels forS. gordoniiat pH 6. The bias for lactic acid production at pH 6 resulted in concomitant improvement in the survival ofS. gordoniiat low pH and seems to constitute part of the acid tolerance response ofS. gordonii. Differential responses to pH similarly affect other oral streptococcal species, suggesting that the observed results are part of a larger phenomenon linking environmental pH, central metabolism, and the capacity to produce antagonistic amounts of H2O2.IMPORTANCEOral biofilms are subject to frequent and dramatic changes in pH.S. sanguinisandS. gordoniican compete with caries- and periodontitis-associated pathogens by generating H2O2. Therefore, it is crucial to understand howS. sanguinisandS. gordoniiadapt to low pH and maintain their competitiveness under acid stress. The present study provides evidence that certain oral bacteria respond to environmental pH changes by tuning their metabolic output in favor of lactic acid production, to increase their acid survival, while others maintain their H2O2production at a constant level. The differential control of H2O2production provides important insights into the role of environmental conditions for growth competition of the oral flora.

Construction of lactic acid-tolerant Saccharomyces cerevisiae by using CRISPR-Cas-mediated genome evolution for efficient d-lactic acid production

2020 ◽  
Vol 104 (21) ◽  
pp. 9147-9158
Author(s):  
Ryosuke Mitsui ◽  
Ryosuke Yamada ◽  
Takuya Matsumoto ◽  
Shizue Yoshihara ◽  
Hayato Tokumoto ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Genome Evolution ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Acid Tolerant

THE EFFECT OF INSULIN ON THE UPTAKE OF MONOSACCHARIDES BY THE RAT LENS

1961 ◽  
Vol 22 (4) ◽  
pp. 361-369 ◽  
Author(s):  
RUTH LEVARI ◽  
W. KORNBLUETH ◽  
E. WERTHEIMER
Keyword(s):  
Lactic Acid ◽  
Glucose Uptake ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Bicarbonate Buffer ◽  
Total Uptake ◽  
Order Of Magnitude ◽  
Normal Rat ◽  
Stimulation Of

SUMMARY 1. A direct stimulatory effect of insulin, in vitro, on the uptake of galactose, glucosamine and some pentoses by the intact lens, has been established. Stimulation of glucose uptake is perceptible only under certain conditions, and was more pronounced in a medium of bicarbonate buffer than in phosphate. 2. Insulin increased lactic acid production from glucose and from galactose. 3. Chronic diabetes decreased galactose uptake. Insulin, in vitro, restored the uptake to the level of that of normal rat lenses. 4. Phloridzin was found to cancel the effect of insulin. 5. The increase in uptake by insulin was of the same order of magnitude for glucose and galactose, irrespective of the total uptake. The decrease in uptake due to diabetes was quantitatively the same as the increase by insulin in normal rat lenses. The effect of insulin on lactic acid production was identical for both hexoses. 6. The possible existence of two pathways of glucose uptake in the rat lens is discussed.

scholarly journals Changes in SAM 2 expression affect lactic acid tolerance and lactic acid production in Saccharomyces cerevisiae

2014 ◽  
Vol 13 (1) ◽  
pp. 147 ◽  
Author(s):  
Laura Dato ◽  
Nadia Berterame ◽  
Maria Ricci ◽  
Paola Paganoni ◽  
Luigi Palmieri ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactic Acid ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Acid Tolerance
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