Abstract
Lactic acid bacteria (LAB) are a group of important beneficial microorganisms for human, but their growth is restricted to the habitats with rich nutrients. In order to develop a simple, low-cost and efficient medium based on the mushroom Pleurotus eryngii, this study evaluated the effects of different treatment methods for the mushroom, concentration of the mushroom, buffers, tween 80, MgSO4·7H2O, MnSO4·4H2O, CuSO4·5H2O, riboflavin and ascorbic acid on the growth of Lactococcus lactis subsp. lactis SLPE1-3. An optimized medium was developed, which was composed of the mushroom at 200 g/L, the buffer sodium acetate at 5 g/L, and riboflavin at 0.5 mg/L. The mushroom was ground, boiled and filtered for the filtrate in advance. In this optimized medium which was named as PSR medium, the population density of SLPE1-3 sharply reached 2.13 × 109 CFU/mL within 18 h of incubation, and still maintained 1.17 × 108 CFU/mL at 120 h. In addition, this study found that 6 kinds of LAB could grow almost well, and maintained high survival in PSR medium compared to M17 or MRS medium, including Lactococcus lactis subsp. lactis, Lactobacillus plantarum, Lactococcus lactis subsp. cremoris, Lactobacillus paracasei, Pediococcus pentosaceus and Lactobacillus rhamnosus. These results showed that PSR medium was a simple, low cost and eurytopic medium for the cultivation of LAB, and could replace MRS or M17 medium in the food industry, biomedicine and laboratory.
Highlights
Lactic acid bacteria (LAB) are a diverse group of Grampositive, nonsporulating, low G + C content bacteria that include cocci and bacilli, such as Lactococcus, Lactobacillus, Streptococcus, Pediococcus and Leuconostoc (D’Souza et al 2012; Wyszyńska et al 2015)
Effect of different buffers on the growth of L. lactis subsp. lactis MRS medium, which was extensively used for culturing various LAB species, contained three kinds of buffers, including ammonium citrate, sodium acetate and dipotassium phosphate
When these buffers were supplemented alone or jointly to the P. eryngii medium, the population density of L. lactis susp. lactis SLPE1-3 was significantly higher than that of the control without any buffer, especially alone sodium acetate at the late stage of incubation (Fig. 3a)
Summary
Lactic acid bacteria (LAB) are a diverse group of Grampositive, nonsporulating, low G + C content bacteria that include cocci and bacilli, such as Lactococcus, Lactobacillus, Streptococcus, Pediococcus and Leuconostoc (D’Souza et al 2012; Wyszyńska et al 2015). It is worthwhile to mention that some strains of LAB could cause serious diseases in neonates, aquatic animals and During the last two decades, LAB are extensively studied and used in food technology and biomedicine because of their commercial potential, especially Lactococcus lactis and some species of the Lactobacillus genus (Aller et al 2014; Wyszyńska et al 2015) These microorganisms are fastidious in nutrient requirements, and their growth is restricted to the habitats with rich nutrients (van Niel and Hahn-Hägerdal 1999; Price et al 2012). These media are composed of diversiform materials, and their prices are very high, such as yeast extract, peptone, polypeptone, soy peptone, beef extract
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