Note - Preliminary Applications of Response Surface Modelling to the Evaluation of Optimal Growth Conditions for Beer-spoiling Pediococcus damnosus

Abstract

Beer‐spoiling lactic acid bacteria (LAB) belong to the most harmful contaminants in the brewing industry and various rapid molecular detection methods have been introduced for the detection of these organisms. However, the enrichment cultivation steps needed prior to detection by molecular methods can extend the duration of the analytical procedure by up to several days. The use of brewery‐specific enrichment cultivation media has been recommended due to the large variety within the group of LAB, as well as differences in the microbes encountered at the breweries. In contrast to using a general medium that may support only the growth of some LAB, the combination of several media could allow detection of all relevant LAB. The aim of the present study was to show the effects of shifts in the cultivation conditions and media on the growth of beer‐spoiling LAB using one of the most frequently encountered species, Pediococcus damnosus, as an example. Based on the variable analysis, significant factors could be recognized and their effects on lag‐times and growth rates were compared by means of response surface modelling.

Brewing microbiology - Lactic acid bacteria and cultivation methods of detection - part II

“…Initial medium is B-MRS with reduced concentrations of all the components and a lower pH (Taskila et al, 2010b). The medium allows the growth of all pediococci used in the study and a wide range of lactobacilli (95.3%), which is consistent with the results of Taskila et al (2010b).…”

“…Výchozí půdou je B-MRS se sníženými koncentracemi všech složek a nižším pH (Taskila et al 2010b). Na půdě rostou všechny pediokoky použité ve studii a široké spektrum laktobacilů (95,3 %), což je v souladu s výsledky studie Taskily et al (2010b).…”

“…Růst u kmenů Lactobacillus byl také nejpomalejší, průměrná detekce růs-tu byla 67 hodin, pediokoky rostly rychleji a srovnatelně s nárůstem v tekutých půdách B-MRS a NBB-B. Médium PDM bylo původně navrženo pro detekci P. damnosus (Taskila et al, 2010b), úspěšně v něm však rostou další druhy pediokoků a také kmeny laktobacilů. V naší studii se v tomto médiu pomnožily všechny kmeny, a to rychlostí stejnou pro oba rody -průměrná doba detekce 46 hodin řadí PDM půdu na druhé místo za HLP médium, ve kterém rostly laktobacily o 10 hodin rychleji.…”

“…Growth of Lactobacillus strains was also the slowest, the average time of detection being 67 hours; pediococci grew faster and comparably with the growth in liquid B-MRS and NBB-B media. PDM medium was originally designed for the detection of P. damnosus (Taskila et al, 2010b), but it successfully supports the growth of other species of pediococci and strains of lactobacilli. In our study, all strains propagated in this medium at the same rate for both genera -the average detection time of 46 hours ranks the PDM medium second after HLP medium in which lactobacilli grew about 10 hours faster.…”

Enrichment Cultivation of Beer-Spoiling Lactic Acid Bacteria

“…Suzuki and coworkers 80 showed that the resuscitation of slowly growing beer spoilers, such as L. lindneri, can be remarkably faster at a low glucose concentration compared to commonly used 10-20 g/L. Similar findings were found in our study 92 , indicating that the use of a lower initial concentration of glucose in MRS could be advantageous in the case of beer samples. The nutrient supply can be arranged either by manual addition of nutrients after a short adaptation phase or by use of slow release techniques.…”