Antimicrobial and immunomodulatory potential of various Lactobacillus reuteri strains is closely connected to their metabolite production profile under given cultivation conditions. We determined the in vitro production of antimicrobial substances such as organic acids, ethanol, and reuterin by four strains of L. reuteri (L. reuteri E, L. reuteri KO5, L. reuteri CCM 3625, and L. reuteri ATCC 55730). All studied L. reuteri strains showed the ability to produce lactic acid, acetic acid, and ethanol with concominant consumption of glucose and together with phenyllactic acid-a potent antifungal compound-with concominant consumption of phenylalanine. The reuterin production from glycerol was confirmed for all analyzed lactobacilli strains except L. reuteri CCM 3625. Production of organic acids, ethanol, and reuterin is significantly involved in antimicrobial activity of lactobacilli which was determined using the dual-culture overlay diffusion method against six indicator bacteria and five indicator moulds. In comparison to the referential L. reuteri ATCC 55730, the highest inhibition potential was observed against Escherichia coli CCM 3988 and Pseudomonas aeruginosa CCM 3955. Among analyzed indicators of moulds, the growth of Alternaria alternata CCM F-128 was the most inhibited by all four analyzed L. reuteri strains. Finally, the immunomodulatory potential of analyzed lactobacilli were proven by the determination of the in vitro production of biogenic amines histamine and tyramine. L. reuteri CCM 3625 was able to produce tyramine, and L. reuteri E and L. reuteri KO5 were able to produce histamine under given cultivation conditions.
We investigated the suitability of rice flour for fermented beverage production using various strains of lactic acid bacteria. Fermentation led to a decrease in pH from 5.04–5.17 to 3.74–4.35. At the same time, total acidity increased (1.28–2.59 g/l) due to lactic acid (0.59–2.76 g/l) and acetic acid (0.11–0.30 g/l) production. Fermentation of rice beverages also caused a gradual decrease in glucose and fructose concentration. Lactic acid bacteria proliferated in the first phases of fermentation, and cell counts reached a maximum after 12 h. The highest growth rate (v<sub>LAB</sub> = 0.44 Log<sub>10</sub> CFU/ml/h) was observed in a sample with the culture of Lactobacillus brevis CCM 1815. Viscosity of beverages decreased significantly after 24 h of fermentation. The highest values of sensory parameters were observed in a monoculture of Lactobacillus plantarum CCM 7039 and in a sample with a mixed culture of Lactobacillus plantarum CCM 7039 and Bifidobacterium longum CCM 4990.
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.
Antimicrobial activity of selected lactic acid cocci and production of organic acidsAntimicrobial activity and production of organic acids by selected lactic acid bacteria were monitored in this study. The largest antimicrobial activity against indicator microorganisms showed Pediococcus sp. G5, whereasStreptococcus thermophilushad no inhibitory effect. The inhibitory effect ofPediococcussp. G5 was strongest againstBacillus subtilis(17.78 %). Lactococci inhibited the growth ofEscherichia coli, Pseudomonas aeruginosaandStaphylococcus aureus(% of inhibition ≤ 5.25). The growth ofAsperglillus flavus, Penicillium funiculosumandRhizopus oryzaewas not inhibited by all of tested cocci. Cocci produced varying quantities of organic acids (lactic acid, acetic acid, succinic acid, etc.). Lactic acid was in large amounts and phenyllactic acid was produced only byPediococcussp. G5 (49.65 mg/L).
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