A kinetic method for calculating the viability of lactic starter cultures

Barreto, M. T. O.; Melo, Eduardo P.; Almeida, Jonas S.; Xavier, Ana M. R. B.; Carrondo, Manuel J.T.

doi:10.1007/bf00167916

Cited by 5 publications

(3 citation statements)

References 16 publications

(17 reference statements)

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“…In this sense, once the growth phase has been detected, it is reliable to consider the presence of nonviable organisms as negligible, and every organism in the sample can be considered as viable. Therefore, the monitoring of the growth phase may enable the estimation of the initial concentration able to develop the observed growth curve (Barreto et al 1991).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of ultraviolet disinfection of microalgae by growth modeling: application to ballast water treatment

et al. 2016

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Ultraviolet disinfection is a frequent option for eliminating viable organisms in ballast water to fulfill international and national regulations. The objective of this work is to evaluate the reduction of microalgae able to reproduce after UV irradiation, based on their growth features. A monoculture of microalgae Tisochrysis lutea was irradiated with different ultraviolet doses (UV-C 254 nm) by a flow-through reactor. A replicate of each treated sample was held in the dark for 5 days simulating a treatment during the ballasting; another replicate was incubated directly under the light, corresponding to the treatment application during de-ballasting. Periodic measurements of cell density were taken in order to obtain the corresponding growth curves. Irradiated samples depicted a regrowth following a logistic curve in concordance with the applied UV dose. By modeling these curves, it is possible to obtain the initial concentration of organisms able to reproduce for each applied UV dose, thus obtaining the dose-survival profiles, needed to determine the disinfection kinetics. These dose-survival profiles enable detection of a synergic effect between the ultraviolet irradiation and a subsequent dark period; in this sense, the UV dose applied during the ballasting operation and subsequent dark storage exerts a strong influence on microalgae survival. The proposed methodology, based on growth modeling, established a framework for comparing the UV disinfection by different devices and technologies on target organisms. This procedure may also assist the understanding of the evolution of treated organisms in more complex assemblages such as those that exist in natural ballast water.

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Section: Introductionmentioning

confidence: 99%

Evaluation of ultraviolet disinfection of microalgae by growth modeling: application to ballast water treatment

et al. 2016

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“…A few authors demonstrated that the harvesting time has a strong impact on cellular parameters such as viability and acidification activity (3,20,24). Béal et al (6) specified that there is an optimal range of time during which to harvest cells in a good physiological state, i.e., at a high cellular concentration and a high acidification activity.…”

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confidence: 99%

“…Bis(1,3-dibutylbarbituric acid) trimethine oxonol [DIBAC 4 (3)] was used to assess the depolarization state of the cells (7). Dual staining was performed in order to differentiate dead cells with PI and depolarized cells with DIBAC 4 (3) in a single analysis.…”

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confidence: 99%

Fermentation pH Influences the Physiological-State Dynamics of Lactobacillus bulgaricus CFL1 during pH-Controlled Culture

Rault

Bouix

Béal

2009

Appl Environ Microbiol

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This study aims at better understanding the effects of fermentation pH and harvesting time on Lactobacillus bulgaricus CFL1 cellular state in order to improve knowledge of the dynamics of the physiological state and to better manage starter production. The Cinac system and multiparametric flow cytometry were used to characterize and compare the progress of the physiological events that occurred during pH 6 and pH 5 controlled cultures. Acidification activity, membrane damage, enzymatic activity, cellular depolarization, intracellular pH, and pH gradient were determined and compared during growing conditions. Strong differences in the time course of viability, membrane integrity, and acidification activity were displayed between pH 6 and pH 5 cultures. As a main result, the pH 5 control during fermentation allowed the cells to maintain a more robust physiological state, with high viability and stable acidification activity throughout growth, in opposition to a viability decrease and fluctuation of activity at pH 6. This result was mainly explained by differences in lactate concentration in the culture medium and in pH gradient value. The elevated content of the ionic lactate form at high pH values damaged membrane integrity that led to a viability decrease. In contrast, the high pH gradient observed throughout pH 5 cultures was associated with an increased energetic level that helped the cells maintain their physiological state. Such results may benefit industrial starter producers and fermented-product manufacturers by allowing them to better control the quality of their starters, before freezing or before using them for food fermentation.Lactic acid bacteria are traditionally used to produce or to preserve various food products such as fermented milks, meats, and vegetables. Their ability to initiate rapid acidification of the raw material is essential to improve the flavor, texture, and safety of these products (11,14). In order to prevent poor fermentation yields and to improve the quality and reliability of the products, it is important to maintain proper control starter production. This control may be achieved by studying the effects of process parameters on the growth kinetics of the bacteria and on their acidification activity and physiological state in growing conditions. Among all process parameters, pH and harvesting time are key factors that strongly influence the physiological state of lactic acid bacteria after fermentation and stabilization.Lactic acid starters are currently produced using pH-controlled pure cultures (6), during which pH is generally regulated at an optimal value by continuously adding sodium hydroxide or ammonia in the bioreactor (23). Various growth characteristics such as maximal biomass concentration, specific growth rate, fermentation time, sugar consumption or growth, and product yields are significantly influenced by the pH control value (1, 4). Optimal pH ranges were therefore determined for several lactic acid bacteria, such as Streptococcus thermophilus (pH 6.5), Lactobac...

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Growth Medium for Culturing Probiotic Bacteria for Applications in Vegetarian Food Products

Heenan

Adams

Hosken

et al. 2002

LWT - Food Science and Technology

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A kinetic method for calculating the viability of lactic starter cultures

Cited by 5 publications

References 16 publications

Evaluation of ultraviolet disinfection of microalgae by growth modeling: application to ballast water treatment

Evaluation of ultraviolet disinfection of microalgae by growth modeling: application to ballast water treatment

Fermentation pH Influences the Physiological-State Dynamics of Lactobacillus bulgaricus CFL1 during pH-Controlled Culture

Growth Medium for Culturing Probiotic Bacteria for Applications in Vegetarian Food Products

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