Quantifying the Significance of Phage Attack on Starter Cultures: a Mechanistic Model for Population Dynamics of Phage and Their Hosts Isolated from Fermenting Sauerkraut

Abstract

We investigated the possibility of using starter cultures in sauerkraut fermentation and thereby reducing the quantity of salt used in the process. This, in turn, would reduce the amount of waste salt that would enter in our water resources. Phage, naturally present in sauerkraut fermentation, could potentially affect the starter cultures introduced. Thus, a mechanistic mathematical model was developed to quantify the growth kinetics of the phage and starter cultures. The model was validated by independent experiments with two Leuconostoc mesenteroides strains isolated from sauerkraut and their corresponding phage. Model simulations and experimental evidence showed the presence of phage-resistant cell populations in starter cultures which replaced phage-sensitive cells, even when the initial phage density (P 0 ) and multiplicity of infection (MOI) were low (P 0 < 1 ؋ 10 3 PFU/ml; MOI < 10 ؊4 ) in the MRS media. Based on the results of model simulation and parameter optimization, it was suggested that the kinetic parameters of phage-host interaction, especially the adsorption rate, vary with the initial phage and host densities and with time. The model was validated in MRS broth. Therefore, the effects of heterogeneity and other environmental factors, such as temperature and pH, should be considered to make the model applicable to commercial fermentations.Traditionally, sauerkraut fermentation is carried out by a small population of lactic acid bacteria (LAB) indigenous to cabbage in the presence of 2 to 3% salt (24). Sauerkraut fermentation is carried out in two stages, a heterofermentative stage followed by a homofermentative stage. Leuconostoc mesenteroides initiates the early heterofermentative stage and is primarily responsible for the quality characteristics, such as flavor and aroma, of sauerkraut (22). Salt serves as a selecting agent for LAB and thus is an important factor in deciding the microbial succession during sauerkraut fermentation. During the fermentation process, excess brine is discharged in effluents from processing plants. Due to the environmental concerns about waste salt disposal and the associated economic issues, it may be desirable to reduce the salt concentration by 50% or more. To ensure quality with low-salt fermentations, starter cultures may be needed to maintain the desired flavor and texture of the finished product.In previous studies, Leuconostoc species have been used as starter cultures for sauerkraut fermentations. The starter cultures were found to prolong the heterolactic fermentation, which is responsible for the characteristic flavor and aroma of sauerkraut (4, 13). Recent studies have investigated the genetics and ecology of bacteriophage from fermentating sauerkraut (20,30). Phage active against several LAB have been isolated from commercial fermentations, including L. mesenteroides, which is a potential starter culture for sauerkraut fermentation (20,30). These studies raised the possibility that phage may interfere with the use of starter cultures in low-salt vegetabl...

Metagenomic Analysis of Kimchi, a Traditional Korean Fermented Food

“…Previous studies have reported that the fermentation temperature and acidity are important determinants of the microbial community composition in kimchi fermentation (5,27). However, our results showed that in addition to temperature and acidity, a new influence, that of bacteriophages, was another clearly important determinant of microbial community dynamics, as in sauerkraut fermentation (31,32,37), especially at the end stages of kimchi fermentation.…”

Sequence Analysis of Leuconostoc mesenteroides Bacteriophage Φ1-A4 Isolated from an Industrial Vegetable Fermentation

“…The average burst size of ⌽1-A4 is 24 particles per infective center. The latency period is about 30 min in MRS broth supplemented with 10 mM CaCl 2 at 30°C based on a one-step growth kinetics curve (56). In addition to infecting its natural host, L. mesenteroides 1-A4, ⌽1-A4 was also found to infect two other L. mesenteroides strains, 1-B8 and 1-E10 (48).…”

“…Recent studies have shown that phages are present in the vegetable fermentations (4,47,48,74,75). Because of the rapid lytic cycle of these phages, they may significantly impact starter cultures and bacterial succession in vegetable fermentations (56). Phages active against L. mesenteroides have been isolated and characterized (48); however, genome sequences have not been reported.…”

Bacteriophage Therapy and the Mutant Selection Window

“…Bacteriophages are able to selectively infect and kill susceptible bacteria, in the process producing large numbers of progeny that are similarly capable and therefore have considerable potential for use as self-replicating pharmaceuticals (21). It has been argued that threshold phenomena determine the success and mode of action of phage therapies (11,(21)(22)(23)29), and the predictions of various pharmacokinetic and pharmacodynamic (PK/PD) models have been tested against in vitro data for a variety of bacterial species (2,11,16,17,24,28). These models are broadly consistent with phage-bacterium interactions observed experimentally, but they do not address the issue of how to prevent or alleviate the possible emergence of phage-resistant bacteria.…”