The effects of limiting nutrients, dilution rate, culture pH, and temperature on the yield constant and anthocyanin accumulation of carrot cells grown in semicontinuous chemostat cultures

1983 ◽  
Vol 25 (2) ◽  
pp. 569-579 ◽  
Author(s):  
D. K. Dougall ◽  
S. LaBrake ◽  
G. H. Whitten
Keyword(s):  
Dilution Rate ◽  
Anthocyanin Accumulation ◽  
Carrot Cells ◽  
Culture Ph ◽  
Chemostat Cultures ◽  
Limiting Nutrients

Evolution of Fusarium graminearum A3/5 grown in a series of glucose-limited chemostat cultures at a high dilution rate

1995 ◽  
Vol 99 (2) ◽  
pp. 173-178 ◽  
Author(s):  
Marilyn G. Wiebe ◽  
Geoffrey D. Robson ◽  
Stephen G. Oliver ◽  
Anthony P.J. Trinci
Keyword(s):  
Dilution Rate ◽  
Fusarium Graminearum ◽  
High Dilution ◽  
Chemostat Cultures ◽  
High Dilution Rate

Some properties of frozen concentrated starters produced by continuous culture

1973 ◽  
Vol 40 (2) ◽  
pp. 157-167 ◽  
Author(s):  
G. T. Lloyd ◽  
E. G. Pont
Keyword(s):  
Continuous Culture ◽  
Dilution Rate ◽  
Cell Activity ◽  
Ph Control ◽  
The Other ◽  
Culture Ph ◽  
Streptococcus Cremoris

SummaryFrozen concentrated cheese starters were prepared from 7Streptococcus cremorisand 2Str. lactisstrains by continuous culture. pH control with NH4OH and Ca(OH)2increased the yield ofStr. cremorisstrains as compared with NaOH, but the resultant cells were smaller and less active. Maximum yields for both species were obtained at a dilution rate of 0·6 and pH 6·3, but withStr. cremoriscell activity was reduced above pH 6·0.Degeneration in continuous culture was observed in the 2Str. lactisstrains, due apparently in one case to the action of a bacteriophage and in the other possibly to selection or to loss of adaptive enzymes.Concentrated starters retained full viability and activity when stored for 10–12 weeks at −110°C, and 94% activity after storage for 4 weeks at −40°C.Cheese made with the concentrated starters ripened normally and was comparable in quality with control cheese made with normal bulk starter.

Variation in the activity levels of selected enzymes of Erwinia amylovora 595 in response to changes in dissolved oxygen tension and growth rate of D-glucose-limited chemostat cultures

1975 ◽  
Vol 21 (3) ◽  
pp. 343-352 ◽  
Author(s):  
D. A. Farago ◽  
L. N. Gibbins
Keyword(s):  
Dissolved Oxygen ◽  
Dilution Rate ◽  
Malate Dehydrogenase ◽  
Oxidase Activity ◽  
Erwinia Amylovora ◽  
Specific Activity ◽  
Activity Levels ◽  
Chemostat Cultures ◽  
Succinate Oxidase

Chemostat cultures of Erwinia amylovora 595, grown in mineral salts – nicotinic acid medium at 30 °C, and limited by D-glucose concentrations in the presence of dissolved oxygen tensions (D.O.T.) greater than about 6 mm Hg, became limited by oxygen availability below about 4 mm Hg. This latter limitation was accompanied by a marked increase in acid production as the D.O.T. was depressed. The transition between D-glucose- and oxygen-limitation was also characterized by a maximum in succinate oxidase activity, and a minimum in the in situ respiration. D-Glyceraldehyde-3-phosphate dehydrogenase and D-fructose-1,6-diphosphate aldolase showed small reductions in specific activity in the region 4–6 mm Hg D.O.T., but further reduction to 2 mm Hg resulted in a marked increase in the specific activity of aldolase. Malate dehydrogenase followed the converse trend, and attained very low activity levels when the D.O.T. decreased beyond the lower limits of detection. The in situ respiration was maximal at 2 mm Hg D.O.T., while potential respiration values were minimal at 2 mm Hg, and maximal at about 8 mm Hg D.O.T. The in situ respiration rate was proportional to dilution rate (D), in presence of excess oxygen, up to 0.18 h−1, after which a marked diminution occurred and continued until the wash-out rate was attained. Succinate oxidase activity decreased with increase in dilution rate, but remained constant above D = 0.18 h−1. Malate dehydrogenase showed a persistent decline with increase in dilution rate, while D-glyceraldehyde-3-phosphate activity increased somewhat at higher dilution rates. The data are interpreted in terms of two transition points, at 6 and 2 mm Hg D.O.T., and of a change from respiratory to fermentative metabolism at low D.O.T., and at high dilution rates.

scholarly journals Effects of Pyruvate Decarboxylase Overproduction on Flux Distribution at the Pyruvate Branch Point inSaccharomyces cerevisiae

1998 ◽  
Vol 64 (6) ◽  
pp. 2133-2140 ◽  
Author(s):  
Pim van Hoek ◽  
Marcel T. Flikweert ◽  
Quirina J. M. van der Aart ◽  
H. Yde Steensma ◽  
Johannes P. van Dijken ◽  
...  
Keyword(s):  
Dilution Rate ◽  
Branch Point ◽  
Flux Distribution ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Multicopy Plasmid ◽  
Aerobic Fermentation ◽  
Gene Encoding ◽  
Chemostat Cultures ◽  
Reference Strains

ABSTRACT A multicopy plasmid carrying the PDC1 gene (encoding pyruvate decarboxylase; Pdc) was introduced in Saccharomyces cerevisiae CEN.PK113-5D. The physiology of the resulting prototrophic strain was compared with that of the isogenic prototrophic strain CEN.PK113-7D and an empty-vector reference strain. In glucose-grown shake-flask cultures, the introduction of thePDC1 plasmid caused a threefold increase in the Pdc level. In aerobic glucose-limited chemostat cultures growing at a dilution rate of 0.10 h−1, Pdc levels in the overproducing strain were 14-fold higher than those in the reference strains. Levels of glycolytic enzymes decreased by ca. 15%, probably due to dilution by the overproduced Pdc protein. In chemostat cultures, the extent of Pdc overproduction decreased with increasing dilution rate. The high degree of overproduction of Pdc at low dilution rates did not affect the biomass yield. The dilution rate at which aerobic fermentation set in decreased from 0.30 h−1 in the reference strains to 0.23 h−1 in the Pdc-overproducing strain. In the latter strain, the specific respiration rate reached a maximum above the dilution rate at which aerobic fermentation first occurred. This result indicates that a limited respiratory capacity was not responsible for the onset of aerobic fermentation in the Pdc-overproducing strain. Rather, the results indicate that Pdc overproduction affected flux distribution at the pyruvate branch point by influencing competition for pyruvate between Pdc and the mitochondrial pyruvate dehydrogenase complex. In respiratory cultures (dilution rate, <0.23 h−1), Pdc overproduction did not affect the maximum glycolytic capacity, as determined in anaerobic glucose-pulse experiments.

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