Physiological implications of class IIa bacteriocin resistance in Listeria monocytogenes strains

Microbiology ◽  
2004 ◽  
Vol 150 (2) ◽  
pp. 335-340 ◽  
Author(s):  
Viveka Vadyvaloo ◽  
Jacky L. Snoep ◽  
John W. Hastings ◽  
Marina Rautenbach
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Consumption Rate ◽  
Biomass Yield ◽  
Specific Growth ◽  
Glucose Consumption ◽  
Acid Fermentation ◽  
Lower Growth ◽  
Glucose Consumption Rate ◽  
Resistant Strains

High-level resistance to class IIa bacteriocins has been directly associated with the absent EIIABMan (MptA) subunit of the mannose-specific phosphoenolpyruvate-dependent phosphotransferase system (PTS) () in Listeria monocytogenes strains. Class IIa bacteriocin-resistant strains used in this study were a spontaneous resistant, L. monocytogenes B73-MR1, and a defined mutant, L. monocytogenes EGDe-mptA. Both strains were previously reported to have the EIIABMan PTS component missing. This study shows that these class IIa bacteriocin-resistant strains have significantly decreased specific growth and glucose consumption rates, but they also have a significantly higher growth yield than their corresponding wild-type strains, L. monocytogenes B73 and L. monocytogenes EGDe, respectively. In the presence of glucose, the strains showed a shift from a predominantly lactic-acid to a mixed-acid fermentation. It is here proposed that elimination of the EIIABMan in the resistant strains has caused a reduced glucose consumption rate and a reduced specific growth rate. The lower glucose consumption rate can be correlated to a shift in metabolism to a more efficient pathway with respect to ATP production per glucose, leading to a higher biomass yield. Thus, the cost involved in obtaining bacteriocin resistance, i.e. losing substrate transport capacity leading to a lower growth rate, is compensated for by a higher biomass yield.

Biofilm monitoring: a perfect solution in search of a problem

2003 ◽  
Vol 47 (5) ◽  
pp. 9-18 ◽  
Author(s):  
Z. Lewandowski ◽  
H. Beyenal
Keyword(s):  
Consumption Rate ◽  
Glucose Consumption ◽  
Data Interpretation ◽  
Integrated System ◽  
Glucose Consumption Rate ◽  
Biofilm Heterogeneity

The main problem with monitoring biofilms is data interpretation. Biofilm heterogeneity causes monitored parameters to vary from location to location in the same biofilm, and it is difficult to assess to what extent these variations are caused by biofilm heterogeneity and to what extent they reflect other properties of the biofilm. We have used the concept of discretized biofilms, which is an integrated system of biofilm monitoring and data interpretation, to assess the effect of biofilm heterogeneity on biofilm activity. Using this approach we have estimated that a heterogeneous biofilm can be ten times more active, in terms of glucose consumption rate, than a homogeneous biofilm of the same thickness but with uniformly distributed density.

scholarly journals Physiological Characterization of an Anaerobic Ammonium-Oxidizing Bacterium Belonging to the “Candidatus Scalindua” Group

2013 ◽  
Vol 79 (13) ◽  
pp. 4145-4148 ◽  
Author(s):  
Takanori Awata ◽  
Mamoru Oshiki ◽  
Tomonori Kindaichi ◽  
Noriatsu Ozaki ◽  
Akiyoshi Ohashi ◽  
...  
Keyword(s):  
Growth Rate ◽  
Specific Growth ◽  
Maximum Specific Growth Rate ◽  
Ammonium Oxidation ◽  
Lower Growth ◽  
Content Type ◽  
Physiological Characterization ◽  
Phylogenetic Affiliation ◽  
Lower Growth Rate

ABSTRACTThe phylogenetic affiliation and physiological characteristics (e.g.,Ksand maximum specific growth rate [μmax]) of an anaerobic ammonium oxidation (anammox) bacterium, “CandidatusScalindua sp.,” enriched from the marine sediment of Hiroshima Bay, Japan, were investigated. “CandidatusScalindua sp.” exhibits higher affinity for nitrite and a lower growth rate and yield than the known anammox species.

scholarly journals KINETIC EVALUATION OF ETHANOL-TOLERANT THERMOPHILE Geobacillus thermoglucosidasius M10EXG FOR ETHANOL PRODUCTION

2016 ◽  
Vol 10 (1) ◽  
pp. 24
Author(s):  
Eny Ida Riyanti ◽  
Peter L. Rogers
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Ethanol Production ◽  
Yeast Extract ◽  
Biomass Yield ◽  
Specific Growth ◽  
Kinetic Evaluation ◽  
Geobacillus Thermoglucosidasius ◽  
Low Level ◽  
Wide Range

Thermophiles are challenging to be studied for ethanol production using agricultural waste containing lignocellulosic materials rich in hexose and pentose. These bacteria have many advantages such as utilizing a wide range of substrates, including pentose (C5) and hexose (C6). In ethanol production, it is important to use ethanol tolerant strain capable in converting lignocellulosic hydrolysate. This study was aimed to investigate the growth profile of ethanol-tolerant thermophile Geobacillus thermoglucosidasius M10EXG using a defined growth medium consisted of single carbon glucose (TGTV), xylose (TXTV), and a mixture of glucose and xylose (TGXTV), together with the effect of yeast extract addition<br />to the media. The experiments were conducted at the School of Biotechnology and Biomolecular Sciences of The University of New South Wales, Australia on a shake flask fermentation at 60°C in duplicate experiment. Cultures were sampled every two hours and analised for their kinetic parameters including the maximum specific growth rate (µmax), biomass yield (Yx/s), ethanol and by-product yields (acetate and L-lactate) (Yp/s), and the doubling time (Td). Results showed that this strain was capable of growing on minimal medium containing glucose or xylose as a single carbon source. This strain utilized glucose and xylose simultaneously (co-fermentation), although there was glucose repression of xylose at relatively low glucose concentration (0.5% w/v), particularly when yeast extract (0.2% w/v) was added to the medium. The highest biomass yield was obtained at 0.5 g l-1 on glucose medium; the yield increased when yeast extract was added (at 0.59 g l-1). The highest specific growth rate of 0.25 was obtained in the phase I growth when the strain was grown on a mixture of glucose and xylose (0.5% : 0.5% w/v) medium. Diauxic growth was shown on the mixture of glucose, xylose, and yeast extract. The strain produced low level of ethanol (0.1 g l-1), as well as low level (0.2 g l-1) of by-products (L-lactate and acetate) after 15 hours. The results suggests its potential application for fermenting lignocellulosic agricultural wastes for ethanol production.

Estimation and control of non-linear variables in a continuous fermentation process using sliding mode techniques

2011 ◽  
Vol 34 (7) ◽  
pp. 769-779 ◽  
Author(s):  
AFNA Rahman ◽  
SK Spurgeon ◽  
XG Yan
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Substrate Concentration ◽  
Fermentation Process ◽  
Consumption Rate ◽  
Specific Growth ◽  
Sliding Mode ◽  
Biomass Concentration ◽  
Substrate Consumption ◽  
Non Linear

Biomass, substrate or metabolite concentrations are difficult to measure online in fermentation processes because of the lack of reliable, cheap and sterilizable transducers. Currently, many of the measurements required may be determined through offline analysis, which is costly and time consuming. Furthermore, the specific growth rate conditions involved in the fermentation are typically non-linear and uncertain. In this paper, a new variable, the substrate consumption rate, consisting of a combination of substrate concentration, biomass concentration, specific growth rate and yield production coefficient, is introduced to overcome these problems and simplify the non-linear differential equations of the fermentation process. A sliding mode observer, which only requires measurement of substrate concentration, is then developed to solve the estimation problem, providing a soft sensor to estimate the substrate consumption rate. It is shown that the sliding mode exhibited by the corresponding observer error dynamics is exponentially stable. This parameterization and the resulting estimate of biomass concentration are then utilized within a feedback control strategy. Non-linear simulation results in the presence of both parameter uncertainties and external disturbances illustrate the approach.

scholarly journals Influence of static magnetic fields on S. cerevisae biomass growth

2007 ◽  
Vol 50 (3) ◽  
pp. 515-520 ◽  
Author(s):  
João B. Muniz ◽  
Milton Marcelino ◽  
Mauricio da Motta ◽  
Alexandre Schuler ◽  
Mauricy Alves da Motta
Keyword(s):  
Magnetic Fields ◽  
Consumption Rate ◽  
Cylindrical Tube ◽  
Glucose Consumption ◽  
Dry Weight ◽  
Biomass Growth ◽  
Glucose Consumption Rate ◽  
Static Magnetic Fields ◽  
Tube Reactor ◽  
Flow Intensity

Biomass growth of Saccharomyces cerevisiae DAUFPE-1012 was studied in eight batch fermentations exposed to steady magnetic fields (SMF) running at 23ºC (± 1ºC), for 24 h in a double cylindrical tube reactor with synchronic agitation. For every batch, one tube was exposed to 220mT flow intensity SMF, produced by NdFeB rod magnets attached diametrically opposed (N to S) magnets on one tube. In the other tube, without magnets, the fermentation occurred in the same conditions. The biomass growth in culture (yeast extract + glucose 2%) was monitored by spectrometry to obtain the absorbance and later, the corresponding cell dry weight. The culture glucose concentration was monitored every two hours so as the pH, which was maintained between 4 and 5. As a result, the biomass (g/L) increment was 2.5 times greater in magnetized cultures (n=8) as compared with SMF non-exposed cultures (n=8). The differential (SMF-control) biomass growth rate (135%) was slightly higher than the glucose consumption rate (130 %) leading to increased biomass production of the magnetized cells.

scholarly journals Overflow Metabolism in Escherichia coli during Steady-State Growth: Transcriptional Regulation and Effect of the Redox Ratio

2006 ◽  
Vol 72 (5) ◽  
pp. 3653-3661 ◽  
Author(s):  
G. N. Vemuri ◽  
E. Altman ◽  
D. P. Sangurdekar ◽  
A. B. Khodursky ◽  
M. A. Eiteman
Keyword(s):  
Escherichia Coli ◽  
Consumption Rate ◽  
Nadh Oxidase ◽  
Glucose Consumption ◽  
Tca Cycle ◽  
Overflow Metabolism ◽  
Glucose Consumption Rate ◽  
Redox Ratio ◽  
E Coli ◽  
Acetate Formation

ABSTRACT Overflow metabolism in the form of aerobic acetate excretion by Escherichia coli is an important physiological characteristic of this common industrial microorganism. Although acetate formation occurs under conditions of high glucose consumption, the genetic mechanisms that trigger this phenomenon are not clearly understood. We report on the role of the NADH/NAD ratio (redox ratio) in overflow metabolism. We modulated the redox ratio in E. coli through the expression of Streptococcus pneumoniae (water-forming) NADH oxidase. Using steady-state chemostat cultures, we demonstrated a strong correlation between acetate formation and this redox ratio. We furthermore completed genome-wide transcription analyses of a control E. coli strain and an E. coli strain overexpressing NADH oxidase. The transcription results showed that in the control strain, several genes involved in the tricarboxylic acid (TCA) cycle and respiration were repressed as the glucose consumption rate increased. Moreover, the relative repression of these genes was alleviated by expression of NADH oxidase and the resulting reduced redox ratio. Analysis of a promoter binding site upstream of the genes which correlated with redox ratio revealed a degenerate sequence with strong homology with the binding site for ArcA. Deletion of arcA resulted in acetate reduction and increased the biomass yield due to the increased capacities of the TCA cycle and respiration. Acetate formation was completely eliminated by reducing the redox ratio through expression of NADH oxidase in the arcA mutant, even at a very high glucose consumption rate. The results provide a basis for studying new regulatory mechanisms prevalent at reduced NADH/NAD ratios, as well as for designing more efficient bioprocesses.

scholarly journals Analytical solution for a hybrid Logistic-Monod cell growth model in batch and CSTR culture

2019 ◽  
Author(s):  
Peng Xu
Keyword(s):  
Growth Rate ◽  
Cell Growth ◽  
Analytical Solution ◽  
Carrying Capacity ◽  
Biomass Yield ◽  
Specific Growth ◽  
Logistic Equation ◽  
Monod Equation ◽  
Limiting Nutrient ◽  
Growth Inhibiting

AbstractMonod and Logistic growth models have been widely used as basic equations to describe cell growth in bioprocess engineering. In the case for Monod equation, specific growth rate is governed by a limiting nutrient, with the mathematical form similar to the Michaelis-Menten equation. In the case for Logistic equation, specific growth rate is determined by the carrying capacity of the system, which could be growth-inhibiting factors (i.e. toxic chemical accumulation) other than the nutrient level. Both equations have been found valuable to guide us build structure-based kinetic models to analyze fermentation process and understand cell physiology. In this work, we present a hybrid Logistic-Monod growth model, which accounts for multiple growth-dependence factors including both the limiting nutrient and the carrying capacity of the system. Coupled with substrate consumption and yield coefficient, we present the analytical solutions for this hybrid Logistic-Monod model in both batch and CSTR culture. Under high biomass yield (Yx/s) conditions, the analytical solution for this hybrid model is approaching to the Logistic equation; under low biomass yield condition, the analytical solution for this hybrid model converges to the Monod equation. This hybrid Logistic-Monod equation represents the cell growth transition from substrate-limiting condition to growth-inhibiting condition, which could be adopted to accurately describe the multi-phases of cell growth and may facilitate kinetic model construction, bioprocess optimization and scale-up in industrial biotechnology.

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