scholarly journals Single Mathematical Parameter for Evaluation of the Microorganisms’ Growth as the Objective Function in the Optimization by the DOE Techniques

2020 ◽  
Vol 8 (11) ◽  
pp. 1706
Author(s):  
Maciej Konopacki ◽  
Adrian Augustyniak ◽  
Bartłomiej Grygorcewicz ◽  
Barbara Dołęgowska ◽  
Marian Kordas ◽  
...  
Keyword(s):  
Objective Function ◽  
Growth Parameter ◽  
Growth Curves ◽  
Culture Conditions ◽  
Lag Phase ◽  
Mathematical Approach ◽  
Phase Duration ◽  
Scientific Disciplines ◽  
Shape Curve ◽  
Model Curve

The cultivation of bacteria sets a ground for studying biological processes in many scientific disciplines. The development of the bacterial population is commonly described with three factors that can be used to evaluate culture conditions. However, selecting only one of them for the optimization protocol is rather problematic and may lead to unintended errors. Therefore, we proposed a novel mathematical approach to obtain a single factor that could be used as the objective function to evaluate the whole growth dynamic and support the optimization of the biomass production process. The sigmoidal-shape curve, which is the commonly used function to plot the amount of biomass versus time, was the base for the mathematical analysis. The key process parameters, such as maximal specific growth rate and lag-phase duration were established with the use of mathematical coefficients of the model curve and combined to create the single growth parameter. Moreover, this parameter was used for the exemplary optimization of the cultivation conditions of Klebsiella pneumoniae that was cultured to be further used in the production of lytic bacteriophages. The proposed growth parameter was successfully validated and used to calculate the optimal process temperature of the selected bacterial strain. The obtained results indicated that the proposed mathematical approach could be effortlessly adapted for a precise evaluation of growth curves.

Comparison of Growth Kinetics for Healthy and Heat-Injured Listeria monocytogenes in Eight Enrichment Broths

2002 ◽  
Vol 65 (8) ◽  
pp. 1333-1337 ◽  
Author(s):  
TODD M. SILK ◽  
TATIANA M. T. ROTH ◽  
C. W. DONNELLY
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Curves ◽  
Lag Phase ◽  
Phase Duration ◽  
Enrichment Broth ◽  
Selective Enrichment ◽  
Gompertz Equation ◽  
Selective Agents ◽  
Time Required ◽  
Maximum Population Density

Detection of Listeria in food products is often limited by performance of enrichment media used to support growth of Listeria to detectable levels. In this study, growth curves were generated using healthy and heat-injured Listeria monocytogenes strain F5069 in three nonselective and five selective enrichment broths. Nonselective enrichment media included the current Food and Drug Administration Bacteriological Analytical Manual Listeria enrichment broth base (BAM), Listeria repair broth (LRB), and Trypticase soy broth. Selective enrichment media included BAM with selective agents and LRB with selective agents, BCM L. monocytogenes preenrichment broth, Fraser broth, and UVM-modified Listeria enrichment broth. The Gompertz equation was used to model the growth of L. monocytogenes. Gompertz parameters were used to calculate exponential growth rate, lag-phase duration (LPD), generation time, maximum population density (MPD), and time required for repair of injured cells. Statistical differences (P < 0.05) in broth performance were noted for LPD and MPD when healthy and injured cells were inoculated into the broths. With the exception of Fraser broth, there were no significant differences in the time required for the repair of injured cells. Results indicate that the distinction between selective and nonselective broths in their ability to grow healthy Listeria and to repair sublethally injured cells is not solely an elementary issue of presence or absence of selective agents.

Control of Listeria monocytogenes on Vacuum-Packaged Frankfurters Sprayed with Lactic Acid Alone or in Combination with Sodium Lauryl Sulfate

2008 ◽  
Vol 71 (4) ◽  
pp. 728-734 ◽  
Author(s):  
OLEKSANDR A. BYELASHOV ◽  
PATRICIA A. KENDALL ◽  
KEITH E. BELK ◽  
JOHN A. SCANGA ◽  
JOHN N. SOFOS
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Sodium Lauryl Sulfate ◽  
Growth Curves ◽  
Lag Phase ◽  
Lauryl Sulfate ◽  
Phase Duration ◽  
Poultry Products ◽  
All Solutions ◽  
Pathogen Populations

U.S. regulations require that processors employ lethal or inhibitory antimicrobial alternatives in production of ready-toeat meat and poultry products that support growth of Listeria monocytogenes and may be exposed to the processing environment after a lethality treatment. In this study, lactic acid (LA; 5%, vol/vol) and sodium lauryl sulfate (SLS; 0.5%, wt/vol) were evaluated individually or as a mixture (LASLS) for control of L. monocytogenes on frankfurters. Frankfurters were inoculated with a 10-strain mixture of L. monocytogenes, sprayed for 10 s (20 bar, 23 ± 2°C) with antimicrobials or distilled water (DW) before (LASLS or DW) or after (LA, SLS, LASLS, or DW) inoculation (4.8 ± 0.1 log CFU/cm2), vacuum packaged, and stored at 4°C for 90 days. Samples were analyzed for numbers of the pathogen (on PALCAM agar) and for total microbial counts (on tryptic soy agar with yeast extract) during storage. Spraying with DW, LA, or SLS after inoculation reduced numbers of L. monocytogenes by 1.3 ± 0.2, 1.8 ± 0.5, and 2.0 ± 0.4 log CFU/cm2, respectively. The LASLS mixture applied before or after inoculation reduced pathogen populations by 1.8 ± 0.4 and 2.8 ± 0.2 log CFU/cm2, respectively. No further reduction by any treatment was observed during storage. The bacterial growth curves (fitted by the model of Baranyi and Roberts) indicated that the lag-phase duration of the bacterium on control samples (13.85 to 15.18 days) was extended by spraying with all solutions containing LA. For example, LA suppressed growth of L. monocytogenes for 39.14 to 41.01 days. Pathogen growth rates also were lower on frankfurters sprayed after inoculation with LA or LASLS compared to those sprayed with DW. Therefore, spraying frankfurters with a mixture of LA and SLS may be a useful antilisterial alternative treatment for ready-to-eat meat and poultry products.

scholarly journals Modeling the Lag Time of Listeria monocytogenes from Viable Count Enumeration and Optical Density Data

2002 ◽  
Vol 68 (12) ◽  
pp. 5816-5825 ◽  
Author(s):  
F. Baty ◽  
J. P. Flandrois ◽  
M. L. Delignette-Muller
Keyword(s):  
Listeria Monocytogenes ◽  
Optical Density ◽  
Growth Parameters ◽  
Growth Models ◽  
Growth Parameter ◽  
Viable Count ◽  
Linear Increase ◽  
Lag Phase ◽  
Parameter Estimates ◽  
Phase Duration

ABSTRACT The following two factors significantly influence estimates of the maximum specific growth rate (μmax) and the lag-phase duration (λ): (i) the technique used to monitor bacterial growth and (ii) the model fitted to estimate parameters. In this study, nine strains of Listeria monocytogenes were monitored simultaneously by optical density (OD) analysis and by viable count enumeration (VCE) analysis. Four usual growth models were fitted to our data, and estimates of growth parameters were compared from one model to another and from one monitoring technique to another. Our results show that growth parameter estimates depended on the model used to fit data, whereas there were no systematic variations in the estimates of μmax and λ when the estimates were based on OD data instead of VCE data. By studying the evolution of OD and VCE simultaneously, we found that while log OD/VCE remained constant for some of our experiments, a visible linear increase occurred during the lag phase for other experiments. We developed a global model that fits both OD and VCE data. This model enabled us to detect for some of our strains an increase in OD during the lag phase. If not taken into account, this phenomenon may lead to an underestimate of λ.

Growth Variation Among Species and Strains of Listeria in Culture Broth

1994 ◽  
Vol 57 (9) ◽  
pp. 765-769 ◽  
Author(s):  
WERNER B. BARBOSA ◽  
LAURA CABEDO ◽  
HEIDI J. WEDERQUIST ◽  
JOHN N. SOFOS ◽  
GLENN R. SCHMIDT
Keyword(s):  
Growth Parameters ◽  
Phosphate Buffer Solution ◽  
Growth Curves ◽  
Culture Broth ◽  
Lag Phase ◽  
Gompertz Function ◽  
Buffer Solution ◽  
Phase Duration ◽  
Growth Variation ◽  
Increasing Temperature

Culture suspensions of 45 species and strains of Listeria were prepared in tryptic soy broth with 0.6% yeast extract (TSBYE) for 24 h at 37°C, and were then diluted with phosphate buffer solution and standardized to 0.10 ± 0.01 absorbance at 600 nm. Spectrophotometer tubes containing 5 ml of TSBYE (pH 7.2) were inoculated with 0.1 ml of the standardized cultures and incubated at 4, 10 or 37°C. Absorbance readings were taken during storage. Growth curves were fitted using the Gompertz function, and growth parameters were calculated. There were major differences in lag phase duration (LPD), generation time (GT) and exponential growth rate (EGR) among species and strains of Listeria tested. Values for LPD and GT decreased (P <0.05) with increasing temperature of incubation, while EGR and maximum population density (MPD) values increased. Lag phase duration and GT values at a given temperature were lower for Listeria monocytogenes compared to other Listeria spp. At 4°C, LPDs for L. monocytogenes strains ranged from 69.8 to 270.8 h. Of the L. monocytogenes cultures tested, strain Scott A had the longest average (209.8 ± 0.1) h LPD at 4°C. At l0°C, LPDs ranged from 36.5 to 68.9 h, with Scott A being again one of the strains with the longest average LPD (62.8 ± 0.7 h). At 37°C, LPDs ranged from 4.4 to 11.1 h. Variation was also observed in GT and EGR, especially at 4°C. Although there were major variations in growth parameters due to strain and temperature, no significant (P >0.05) trends were observed in average values among different serotypes of L. monocytogenes tested.

Growth Kinetics of Listeria Isolated from Salmon and Salmon Processing Environment: Single Strains versus Cocktails

2012 ◽  
Vol 75 (7) ◽  
pp. 1227-1235 ◽  
Author(s):  
TORSTEIN SKÅRA ◽  
ASTRID M. CAPPUYNS ◽  
EVA VAN DERLINDEN ◽  
JAN THOMAS ROSNES ◽  
VASILIS P. VALDRAMIDIS ◽  
...  
Keyword(s):  
Growth Rate ◽  
Relative Rate ◽  
Growth Parameter ◽  
Optimal Growth ◽  
Maximum Growth ◽  
Estimation Methods ◽  
Lag Phase ◽  
Phase Duration ◽  
Average Growth ◽  
Single Strain

The growth dynamics of Listeria monocytogenes strains isolated from salmon or a salmon processing environment and two reference Listeria innocua strains were investigated at refrigerated and close-to-optimal growth temperatures. Estimates for the growth rates and the lag-phase duration at 4, 8, 12, and 30°C were obtained for optical density measurements by using different growth parameter estimation methods, i.e., the serial dilution (SD) method and the relative rate to detection (RRD) method. Both single L. innocua and L. monocytogenes strains and mixtures of L. monocytogenes strains (cocktails) were studied. Both methods show an increase in maximum growth rate (μmax) of Listeria with increasing temperatures. Generally, single-strain growth rate estimates were quite similar for both species, although L. monocytogenes showed slightly higher μmax estimates at 4°C. The SD method gave the highest estimates for the growth rate, i.e., the estimates from the RRD method were 10 to 20% lower. This should lead to caution when using the latter method for Listeria, particularly at lower temperatures. Overall, the SD method is preferred as this method yields μmax estimates close to the biological value and provides estimates for the duration of lag time (λ). For discrimination between different strains, λ appeared to be a more suitable parameter than μmax. This effect was most prominent for L. innocua. Significant differences were observed between μmax and/or λ of L. monocytogenes cocktails and single strains at all temperatures investigated. At 4°C, the average growth rate of cocktails was higher than that of single strains. At 8 and 30°C, this trend was reversed. The average λ of single strains were more than twice as long as those of cocktails at 4°C. At 8 and 30°C, the λ of cocktails were significantly slower than those of single strains, but the variation was considerably less and the differences were less pronounced.

Growth Kinetics and Cell Morphology of Listeria monocytogenes Scott A as Affected by Temperature, NaCl, and EDTA†,‡

2003 ◽  
Vol 66 (7) ◽  
pp. 1208-1215 ◽  
Author(s):  
LAURA L. ZAIKA ◽  
JOSEPH S. FANELLI
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Kinetics ◽  
Morphological Characteristics ◽  
Brain Heart Infusion ◽  
Growth Curves ◽  
Stress Conditions ◽  
Plate Count ◽  
Lag Phase ◽  
Kinetics Parameters ◽  
Phase Duration

Growth kinetics and morphological characteristics of Listeria monocytogenes Scott A grown under stress conditions induced by increasing levels of NaCl and EDTA were studied as a function of temperature. L. monocytogenes Scott A was inoculated into brain heart infusion broth (pH 6) at 19, 28, 37, and 42°C. Test cultures contained NaCl (at concentrations of 4.5, 6.0, and 7.5%) or EDTA (at concentrations of 0.1, 0.2, and 0.3 mM); control cultures contained 0.5% NaCl. Growth curves were fitted from plate count data by the Gompertz equation, and growth kinetics parameters were derived. Stationary-phase cells were examined by scanning and transmission electron microscopy. Generation times (GTs) and lag phase duration times (LPDs) increased as additive levels were increased. The bacterium grew at all NaCl levels. At 37 and 42°C, growth was slow in media containing 7.5% NaCl, and no growth occurred in media containing 0.3 mM EDTA. Temperature was a major factor in certain stress conditions that led to cell elongation and loss of flagella. Cells in control media at 28°C grew as short rods (0.5 by 1.0 to 2.0 μm), while at 42°C most cells were 4 to 10 times as long. Higher levels of NaCl at higher temperatures resulted in longer and thicker cells. At 28°C, 0.1 mM EDTA had little effect on growth kinetics and morphology; however, 0.3 mM EDTA caused a sixfold increase in GT and LPD and loss of flagellae, with most cells being two to six times as long as normal. Cell length did not correlate with growth kinetics. The results of this study suggest that the effect of altered morphological characteristics of L. monocytogenes cells grown under stress on the virulence and subsequent survival of these cells should be investigated.

scholarly journals Reciprocal hemizygosity analysis reveals that the Saccharomyces cerevisiae CGI121 gene affects lag time duration in synthetic grape must

2021 ◽  
Author(s):  
Runze Li ◽  
Rebecca C Deed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperatures ◽  
Lag Time ◽  
Lag Phase ◽  
Phenotypic Traits ◽  
Time Duration ◽  
Phase Duration ◽  
Grape Must ◽  
The Impact ◽  
Reciprocal Hemizygosity Analysis

Abstract It is standard practice to ferment white wines at low temperatures (10-18 °C). However, low temperatures increase fermentation duration and risk of problem ferments, leading to significant costs. The lag duration at fermentation initiation is heavily impacted by temperature; therefore, identification of Saccharomyces cerevisiae genes influencing fermentation kinetics is of interest for winemaking. We selected 28 S. cerevisiae BY4743 single deletants, from a prior list of open reading frames (ORFs) mapped to quantitative trait loci (QTLs) on chromosomes VII and XIII, influencing the duration of fermentative lag time. Five BY4743 deletants, Δapt1, Δcgi121, Δclb6, Δrps17a, and Δvma21, differed significantly in their fermentative lag duration compared to BY4743 in synthetic grape must (SGM) at 15 °C, over 72 h. Fermentation at 12.5 °C for 528 h confirmed the longer lag times of BY4743 Δcgi121, Δrps17a, and Δvma21. These three candidate ORFs were deleted in S. cerevisiae RM11-1a and S288C to perform single reciprocal hemizygosity analysis (RHA). RHA hybrids and single deletants of RM11-1a and S288C were fermented at 12.5 °C in SGM and lag time measurements confirmed that the S288C allele of CGI121 on chromosome XIII, encoding a component of the EKC/KEOPS complex, increased fermentative lag phase duration. Nucleotide sequences of RM11-1a and S288C CGI121 alleles differed by only one synonymous nucleotide, suggesting that intron splicing, codon bias, or positional effects might be responsible for the impact on lag phase duration. This research demonstrates a new role of CGI121 and highlights the applicability of QTL analysis for investigating complex phenotypic traits in yeast.

scholarly journals Predictive Modeling for the Growth of Salmonella spp. in Liquid Egg White and Application of Scenario-Based Risk Estimation

2021 ◽  
Vol 9 (3) ◽  
pp. 486
Author(s):  
Mi Seon Kang ◽  
Jin Hwa Park ◽  
Hyun Jung Kim
Keyword(s):  
Predictive Model ◽  
Scenario Analysis ◽  
Specific Growth ◽  
Risk Estimation ◽  
Egg White ◽  
Lag Phase ◽  
Salmonella Spp ◽  
Baseline Model ◽  
Phase Duration ◽  
Root Model

The objective of the study was to develop a predictive model of Salmonella spp. growth in pasteurized liquid egg white (LEW) and to estimate the salmonellosis risk using the baseline model and scenario analysis. Samples were inoculated with six strains of Salmonella, and bacterial growth was observed during storage at 10–37 °C. The primary models were developed using the Baranyi model for LEW. For the secondary models, the obtained specific growth rate (μmax) and lag phase duration were fitted to a square root model and Davey model, respectively, as functions of temperature (R2 ≥ 0.98). For μmax, the values were satisfied within an acceptable range (Af, Bf: 0.70–1.15). The probability of infection (Pinf) due to the consumption of LEW was zero in the baseline model. However, scenario analysis suggested possible salmonellosis for the consumption of LEW. Because Salmonella spp. proliferated much faster in LEW than in egg white (EW) during storage at 20 and 30 °C (p < 0.01), greater Pinf may be obtained for LEW when these products are stored at the same conditions. The developed predictive model can be applied to the risk management of Salmonella spp. along the food chain, including during product storage and distribution.

scholarly journals Biomethane Potential of Sludges from a Brackish Water Fish Hatchery

2021 ◽  
Vol 11 (2) ◽  
pp. 552
Author(s):  
Francesco da Borso ◽  
Alessandro Chiumenti ◽  
Giulio Fait ◽  
Matia Mainardis ◽  
Daniele Goi
Keyword(s):  
Brackish Water ◽  
Gompertz Model ◽  
Experimental Tests ◽  
Lag Phase ◽  
Phase Duration ◽  
Fish Hatchery ◽  
Volatile Solids ◽  
Water Recirculation ◽  
Methane Potential ◽  
Intensive Aquaculture

The development of intensive aquaculture is facing the challenge of the sustainable management of effluents. The reproductive sectors (i.e., hatcheries) mainly use water recirculation systems (RAS), which discharge a portion of wastewater. Anaerobic digestion (AD) could reduce the environmental impact of this waste stream while producing biogas. The study is focused on the biochemical methane potential (BMP) of brackish fish hatchery sludges. Wastewater was concentrated by microfiltration and sedimentation and thickened sludges were treated in a BMP system with different inoculum/substrate (I/S) volatile solids ratios (from 50:1 to no inoculum). The highest I/S ratio showed the highest BMP (564.2 NmL CH4/g VS), while different I/S ratios showed a decreasing trend (319.4 and 127.7 NmL CH4/g VS, for I/S = 30 and I/S = 3). In absence of inoculum BMP resulted of 62.2 NmL CH4/g VS. The kinetic analysis (modified Gompertz model) showed a good correlation with the experimental data, but with a long lag-phase duration (from 14.0 to 5.5 days) in particular with the highest I/S. AD applied to brackish water sludges can be a promising treatment with interesting methane productions. For a continuous, full-scale application further investigation on biomass adaptation to salinity and on retention times is needed. Further experimental tests are ongoing.

scholarly journals Growth of Listeria monocytogenes in Thawed Frozen Foods

2017 ◽  
Vol 80 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Ai Kataoka ◽  
Hua Wang ◽  
Philip H. Elliott ◽  
Richard C. Whiting ◽  
Melinda M. Hayman
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Quadratic Model ◽  
Lag Phase ◽  
Frozen Foods ◽  
Phase Duration ◽  
Primary Model

ABSTRACT The growth characteristics of Listeria monocytogenes inoculated onto frozen foods (corn, green peas, crabmeat, and shrimp) and thawed by being stored at 4, 8, 12, and 20°C were investigated. The growth parameters, lag-phase duration (LPD) and exponential growth rate (EGR), were determined by using a two-phase linear growth model as a primary model and a square root model for EGR and a quadratic model for LPD as secondary models, based on the growth data. The EGR model predictions were compared with growth rates obtained from the USDA Pathogen Modeling Program, calculated with similar pH, salt percentage, and NaNO2 parameters, at all storage temperatures. The results showed that L. monocytogenes grew well in all food types, with the growth rate increasing with storage temperature. Predicted EGRs for all food types demonstrated the significance of storage temperature and similar growth rates among four food types. The predicted EGRs showed slightly slower rate compared with the values from the U.S. Department of Agriculture Pathogen Modeling Program. LPD could not be accurately predicted, possibly because there were not enough sampling points. These data established by using real food samples demonstrated that L. monocytogenes can initiate growth without a prolonged lag phase even at refrigeration temperature (4°C), and the predictive models derived from this study can be useful for developing proper handling guidelines for thawed frozen foods during production and storage.

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