Three wild strains of Lactobacillus plantarum were investigated for their growth and ability to produce lactic acid, acetic acid and ethanol under aerobic and anaerobic conditions. They were tested at three different temperatures (30 °C, 37 °C and 45 °C). The growth of lactobacilli was studied by measuring optical density (OD) at λ = 600 nm and pH value at the following times. With increasing temperature difference of cell yield was observed. The fi nal cell yield under aerobic conditions was higher. Organic acids and ethanol were analysed using an HPLC RID method. Formation of lactic acid (as the major metabolite) was the slowest during cultivation at 30 °C, but the fi nal amount of lactic acid showed the highest values. Concentrations of metabolites produced by lactobacilli after 48th hours of cultivation were: 9.18-11.48 g.dm -3 (lactic acid), 0.84-1.65 g.dm -3 (acetic acid) and 2.51-4.03 g.dm -3 (ethanol). No signifi cant differences (p = 0.05) were found in production of lactic acid and ethanol by different bacterial strains under aerobic and anaerobic conditions. Statistically signifi cant differences (p = 0.05) were observed in production of acetic acid by 2L2 under aerobic and anaerobic conditions and for production of ethanol under anaerobic conditions by strains 1L5 and 2L2.
Smetanková J., Hladíková Z., Zimanová M., Greif G., Greifová M. (2014): Lactobacilli isolated from lump sheep's cheeses and their antimicrobial properties. Czech J. Food Sci., 32: 152-157.A total of 34 strains of lactobacilli were isolated from the lump sheep's cheeses produced from raw sheep milk. The strains were identified by MALDI-TOF MS, and 20 of them demonstrating the best fermentation and sensoric properties in milk were chosen and tested for their antimicrobial activity. All selected strains were active against the indicator bacteria and moulds. The highest inhibitory effect was observed with the strains lactobacillus paracasei 314, l. paracasei 316, l. plantarum K816, l. plantarum L718, and l. plantarum 2L2. The subsequent research was focused on the metabolites causing this inhibition. The production of lactic and acetic acids was studied under different cultivation conditions (0, 2, 4, and 6.5% NaCl addition; cultivation at 15, 30, 37, and 45°C; and pH value of the broth before sterilisation 5 and 9). l. plantarum L718 produced the highest concentration of lactic and acetic acids under most of the cultivation conditions. Antimicrobial substances such as phenyllactic acid (62.54-101.62 mg/dm 3 ), H 2 O 2 (0.78-2.30 μg/cm 3 ), and diacetyl (produced by l. plantarum K816 and L718) were studied as well. Keywords: lactobacillus plantarum; lactobacillus paracasei; antimicrobial potentialIt is known that the natural microflora, present in the traditional biotechnological processes during manufacturing, participates in the production of the characteristic aroma, taste, and texture of different cheeses. At first, only artisanal starters were used for the dairy although fermentations. Although they are still used in certain cases, their microbiological instability promoted the evolution of more precisely defined mixtures of lactic acid bacteria (LAB). As cheesemaking became more industrialised, pasteurised milk and standardised bacterial and fungal inocula were introduced with the aim of obtaining a more stable acidifying activity and consistent quality of the products (Carminati et al. 2010). In spite of this trend, the production of raw milk cheeses is still significant, as consumers seek organic foods or traditional sensory characteristics. However, the diversity of microbial populations that have developed in the original cheesemaking environments is largely undefined and is a valuable source of new strains for commercial uses (Laurenčík et al. 2008). For example, non-starter LABs with the potential to inhibit the undesirable microflora are used in the biopreservation of foods (Rodríguez et al. 2000).As far as the technology is concerned, several characteristic properties of the bacterial strains of LAB (acid production in different media and at different temperatures, proteinase and peptidase activities, autolysis, production of volatile compounds, resistance to bacteriophages, production of inhibitory compounds) are important for their use as starters or adjuncts and have been evaluated in the sc...
<p><em>Lactococcus lactis</em> species is one of the most important groups of lactic acid bacteria that are used in the dairy industry. <em>Lactococci </em>are generally found on plants and the skins of animals. Special interest is placed on the study of <em>Lactococcus lactis</em> ssp. <em>lactis</em> and <em>Lactococcus lactis</em> ssp. <em>cremoris</em>, as they are the strains used as starter cultures in industrial dairy fermentation. The major functions of this species in dairy fermentation are the production of lactic acid, formation of flavour and aroma compounds, development of ripened cheese texture and antimicrobial activity against spoilage bacteria and moulds.<br /><br /><strong>doi:10.5219/162</strong></p>
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