Microaerophilic conditions support elevated mixed culture polyhydroxyalkanoate (PHA) yields, but result in decreased PHA production rates

2012 ◽  
Vol 65 (2) ◽  
pp. 243-246 ◽  
Author(s):  
S. Pratt ◽  
A. Werker ◽  
F. Morgan-Sagastume ◽  
P. Lant
Keyword(s):  
Mixed Culture ◽  
Oxygen Limitation ◽  
Mixed Cultures ◽  
Biomass Growth ◽  
Production Rates ◽  
Early Stages ◽  
Batch Systems ◽  
Accumulation Capacity ◽  
Pha Production ◽  
Microaerophilic Conditions

For commercial polyhydroxyalkanoate (PHA) production the objective is to maximise the fraction of feedstock that ends up as polymer, and minimise biomass growth. In this paper, oxygen limitation was applied to achieve this. Intracellular PHA content in mixed cultures in batch systems operated with low and high DO was compared. It is shown that in microaerophilic conditions a higher fraction of substrate is accumulated as PHA in comparison to high DO conditions, evidenced by elevated intracellular PHA content: in the order of 50% higher in the early stages of accumulation. However, the accumulation capacity is not affected by DO. The PHA content in biomass in both the low and high DO systems reached approximately 35%. The time taken for the PHA content in the low DO system to reach capacity was three times longer than in the high DO system.

scholarly journals Hydrogen Production by Geobacter Species and a Mixed Consortium in a Microbial Electrolysis Cell

2009 ◽  
Vol 75 (24) ◽  
pp. 7579-7587 ◽  
Author(s):  
Douglas F. Call ◽  
Rachel C. Wagner ◽  
Bruce E. Logan
Keyword(s):  
Hydrogen Production ◽  
Mixed Culture ◽  
Applied Voltage ◽  
Energy Recovery ◽  
Hydrogen Gas ◽  
Geobacter Sulfurreducens ◽  
Mixed Cultures ◽  
Production Rates ◽  
Current Densities ◽  
Microbial Electrolysis

ABSTRACT A hydrogen utilizing exoelectrogenic bacterium (Geobacter sulfurreducens) was compared to both a nonhydrogen oxidizer (Geobacter metallireducens) and a mixed consortium in order to compare the hydrogen production rates and hydrogen recoveries of pure and mixed cultures in microbial electrolysis cells (MECs). At an applied voltage of 0.7 V, both G. sulfurreducens and the mixed culture generated similar current densities (ca. 160 A/m3), resulting in hydrogen production rates of ca. 1.9 m3 H2/m3/day, whereas G. metallireducens exhibited lower current densities and production rates of 110 ± 7 A/m3 and 1.3 ± 0.1 m3 H2/m3/day, respectively. Before methane was detected in the mixed-culture MEC, the mixed consortium achieved the highest overall energy recovery (relative to both electricity and substrate energy inputs) of 82% ± 8% compared to G. sulfurreducens (77% ± 2%) and G. metallireducens (78% ± 5%), due to the higher coulombic efficiency of the mixed consortium. At an applied voltage of 0.4 V, methane production increased in the mixed-culture MEC and, as a result, the hydrogen recovery decreased and the overall energy recovery dropped to 38% ± 16% compared to 80% ± 5% for G. sulfurreducens and 76% ± 0% for G. metallireducens. Internal hydrogen recycling was confirmed since the mixed culture generated a stable current density of 31 ± 0 A/m3 when fed hydrogen gas, whereas G. sulfurreducens exhibited a steady decrease in current production. Community analysis suggested that G. sulfurreducens was predominant in the mixed-culture MEC (72% of clones) despite its relative absence in the mixed-culture inoculum obtained from a microbial fuel cell reactor (2% of clones). These results demonstrate that Geobacter species are capable of obtaining similar hydrogen production rates and energy recoveries as mixed cultures in an MEC and that high coulombic efficiencies in mixed culture MECs can be attributed in part to the recycling of hydrogen into current.

Impact of Transfaunation of Rumen Ciliate Cultures on Physical Examination, Selected Serum Parameters and Milk Profile in Defaunated Lactating Dairy Goats

2020 ◽  
Keyword(s):  
Physical Examination ◽  
Mixed Culture ◽  
Pure Culture ◽  
Milk Fat ◽  
Mixed Cultures ◽  
Dairy Goats ◽  
Serum Parameters ◽  
Native Breed ◽  
Culture Duration ◽  
Inorganic Phosphorous

Rumen ciliates still have mysterious secrets and influences in ruminants. This study investigated the effect of transfaunation of pure and mixed cultures of rumen ciliates on physical clinical examination, selected serum parameters and milk profile in defaunated lactating dairy goats. A number of 8 Baladi native breed goats were randomly classified into two groups each one containing 4 goats. Pure culture group was transfaunated with 6 ml of pure culture of Holotricha spp., while mixed culture group was transfaunated with 6 ml of mixed culture of 81.85% Holotricha and 18.15% Ophryoscolex spp. once weekly for three consecutive weeks, after defaunation of both groups using 30 ml of 8% SLS for two consecutive days. Serum and milk samples were collected weekly for three successive weeks to study effect of type of ciliate culture, duration of transfaunation and their interaction. Results revealed that transfaunation of pure and mixed cultures of rumen ciliates had no effect on physical examination with minimal non-significant improvement of calcium, inorganic phosphorous, total protein and globulin in serum of defaunated goats. Transfaunation of pure or mixed cultures of rumen ciliates within three weeks could not improve significantly decreased milk fat % of defaunated goats without any effect on other measured milk profile parameters. It is concluded that further investigations on transfaunation without prior defaunation should be performed using different pure and mixed cultures of rumen ciliates for therapeutic and productive purposes.

Note on the effect of temperature on a mixed culture of two organisms in symbiotic relation

1939 ◽  
Vol 29 (2) ◽  
pp. 302-305 ◽  
Author(s):  
E. H. Richards
Keyword(s):  
Nitrogen Fixation ◽  
Mixed Culture ◽  
Azotobacter Chroococcum ◽  
Mixed Cultures ◽  
Effect Of Temperature ◽  
Two Temperatures ◽  
Symbiotic Relation

1. A study was made of nitrogen-fixation byAzotobacter chroococcumalone in a medium containing dextrose (which it can utilize) and in mixture with a coliform organism on a medium containing no carbohydrate except starch, whichAzotobactercannot utilize unless it be hydrolysed by the coliform organism or some other agency.2. The amount of nitrogen fixed in the mixed cultures was found to be maximal at two temperatures, and a discussion is given of the causes thought to be operative in producing the double maximum.

Enhanced PHA Production with Mixed Cultures Using a Robust and Simple Controller

2018 ◽  
Vol 11 (1) ◽  
pp. 277-290
Author(s):  
Gerardo Muñoz ◽  
Alejandro Vargas
Keyword(s):  
Mixed Cultures ◽  
Pha Production

Experimentelle Rotlauf- und Streptokokken-Endokarditis bei der Ratte

1971 ◽  
Vol 8 (2) ◽  
pp. 146-174 ◽  
Author(s):  
A. Kast ◽  
M. Herbst ◽  
L. Stoll
Keyword(s):  
Endothelial Cells ◽  
Mixed Culture ◽  
Bacterial Endocarditis ◽  
Mixed Cultures ◽  
The Other ◽  
Male Rats ◽  
Bacterial Colonisation ◽  
Intravenous Injections ◽  
Single And Mixed Cultures

The ability of intravenous injections of single and mixed cultures of streptococci of types A, C, D, E, G, and N, of S. viridans and of E. rhusiopathiae of serotypes A and B, to cause endocarditis in rats was tested. A mixed culture of three strains of Erysipelothrix was particularly effective, especially in male rats, whereas in all the other experiments, bacterial endocarditis seldom occurred. The endocarditis was a consequence of vasculitis and myocarditis. In most cases of valvular endocarditis subendothelial edema caused detachment of endothelial cells and provided the environment for bacterial colonisation of the valves.

Determination of Kinetic Constants of Activated Sludge Microorganisms

1985 ◽  
Vol 17 (2-3) ◽  
pp. 259-272 ◽  
Author(s):  
J. S. Čech ◽  
J. Chudoba ◽  
P. Grau
Keyword(s):  
Activated Sludge ◽  
Mixed Culture ◽  
Removal Rate ◽  
Mixed Cultures ◽  
Kinetic Constants ◽  
Type Reactor ◽  
Substrate Removal ◽  
Velocity Coefficient ◽  
Mixed Reactor

A respirometric method for measuring kinetic constants of activated sludge microorganisms by means of a simple respirometer was developed and tested by using two types of mixed culture. It has been found that both the maximum substrate removal rate and the half-velocity coefficient are basically lower with the mixed cultures cultivated in a completely-mixed reactor /filamentous/ than with those cultivated in a selector-type reactor /nonfilamentous/.

Elevated Atmosphere Partial Pressure of CO2 and Plant Growth. III. Interactions Between Triticum aestivum (C3) and Echinochloa frumentacea (C4) During Growth in Mixed Culture Under Different CO2, N Nutrition and Irradiance Treatments, With Emphasis on Below-Ground Responses Estimated Using the δ13C Value of Root Biomass

1991 ◽  
Vol 18 (2) ◽  
pp. 137 ◽  
Author(s):  
SC Wong ◽  
CB Osmond
Keyword(s):  
Triticum Aestivum ◽  
Mixed Culture ◽  
Elevated Co2 ◽  
Root Biomass ◽  
Shoot Growth ◽  
Mixed Cultures ◽  
C4 Plants ◽  
C3 Plants ◽  
Δ13c Value ◽  
Echinochloa Frumentacea

Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3 : 1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and 640 μbar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500 �mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3-). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from δ13C value of total root biomass. In air (320 μbar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest but C4 plants had over- taken them by the time of the second harvest. Elevated atmospheric CO2 (640 μbar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3-. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N treatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative δ13C values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Echinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.

scholarly journals Nutritional value changes in response to temperature, microalgae mono and mixed cultures

2019 ◽  
Vol 31 ◽  
Author(s):  
Frederico Pacheco Militão ◽  
Valéria de Oliveira Fernandes ◽  
Kathiani Victor Bastos ◽  
Aline Paternostro Martins ◽  
Pio Colepicolo ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Mixed Culture ◽  
Cell Density ◽  
Total Lipid ◽  
Biochemical Composition ◽  
Essential Fatty Acids ◽  
Scenedesmus Obliquus ◽  
Total Lipid Content ◽  
Mixed Cultures ◽  
Significant Difference

Abstract Aim The response of mixed cultures and monocultures of Pseudopediastrum boryanum (Turpin) E. Hegewald and Scenedesmus obliquus (Turpin) Kützing was assessed in the laboratory at three different temperatures: 20, 30 and 40 °C. The change in biomass and biochemical composition of these cultures was evaluated. Methods Microalgae were placed in a batch culture over 21-days in ASM1 medium. Cell density was directly counted every two days using a Fuchs-Rosenthal hemocytometer. Chlorophyll ‘a’ and total carotenoids were extracted twice. Protein, carbohydrate, total lipid and fatty acid contents were determined at the end of the experiment. Results Cultures grown in 40 °C exhibited no growth. However, there was increased cell density (13.6 x 106 cell.mL-1) and biomass (55 g.L-1) in the S. obliquus monoculture at 30 °C. High protein concentrations (672.6 mg.g-1) were observed in monocultures P. boryanum and S. obliquus at 20 °C treatments. There were high carbohydrate concentrations (6.17 mg.g-1) in P. boryanum unialgal at 30 °C. There was no significant difference in total lipid content between S. obliquus (95.5 mg.g-1), P. boryanum (96.3 mg.g-1) and the mixed culture at 20 °C (105.3 mg.g-1). FAMEs varied significantly regarding the number of unsaturated components, which predominantly consisted of fatty acids with two or more unsaturated bonds. Conclusions The biomass of the treatments analyzed was rich in proteins and essential fatty acids (such as linolenic acid), yet low in carbohydrate content, suggesting its potential use as a food supplement. Our results indicate that mixed culture of P. boryanum and S. obliquus was inefficient in cultivating biomass or biochemical compounds as compared to the unialgal cultivations. However, algae grown together showed better stability in their biochemical composition in response to changes in temperature, an important factor for microalgae production in open ponds and in food safety measures. These results suggest the consortia among different species of microalgae should be tested to determine better methodologies for the production of biomass and metabolites with greater stability towards environmental factors.

Mixed Culture Fermentations To Improve Nutritional Value of Corn Meal1

1988 ◽  
Vol 51 (11) ◽  
pp. 866-868
Author(s):  
M. L. FIELDS ◽  
A. AL-SHOSHAN ◽  
Y. POOSIRI
Keyword(s):  
Amino Acid ◽  
Mixed Culture ◽  
Nutritional Value ◽  
Nutritive Value ◽  
Mixed Cultures ◽  
Corn Meal ◽  
One Step ◽  
Significant Change ◽  
Amino Acid Balance ◽  
Relative Nutritive Value

One-step fermentation involving two microorganisms inoculated at the same time and two-step fermentations involving two inoculations of different microbes at different times were used to enrich corn meal. Starch in corn meal was first hydrolyzed by amylases of B. stearothermophilus, E. fibuligera or A. oryzae followed by the growth of C. utilis. The combination of E. fibuligera and C. utilis produced a significant (P<0.05) increase in lysine, methionine, tryptophan. The relative nutritive value (%), which reflected the amino acid balance, increased significantly (P<0.05) with this sequence of microorganisms. Niacin, riboflavin, and thiamin increased significantly (P<0.05) when mixed cultures of A. oryzae and E. fibuligera in combination with C. utilis were employed. When E. fibuligera alone was grown, no significant change was observed in thiamin content but significant increases occurred in niacin and riboflavin. A. oryzae by itself produced significant (P<0.05) changes in niacin, riboflavin and thiamin.

Sign in / Sign up

Export Citation Format

Share Document