Japanese Journal of Dairy and Food Science. 45 (1996)

【Objective】

We examined antibacterial activities of Enterococcus faecalis TH10 against methicillin-resistant Staphylococcus aureus (MRSA) which is known as a bacterium causing nosocomial infection.

【Methods】

We extracted culture supernatant fluids of Enterococcus faecalis TH10. We prepared the extract apt for the test and performed an antibacterial test with a paper disk method.

【Results】

The prepared extract from culture supernatant fluids of Enterococcus faecalis TH10 showed a potent antibacterial activity against MRSA and a modest antibacterial activity against methicillin-sensitive Staphylococcus aureus. No antibacterial activity was observed in Enterococcus genus. We considered that Enterococcus faecalis TH10 is different from bacteriocin which shows antibacterial activity against the related species of lactic acid bacteria.    

Journal of Food Science and Technology. 41, 469-474 (1994)

【Objective】

Organic acids which microorganisms produce play an important role to add flavor and acidity to fermented foods. However, the degree of acidity and quality varies based on each organic acid. When the balance between the acidity and quality of organic acids is improper, the taste becomes bad. There were not many studies about fumarase, one of the lactic acid bacteria which transforms fumaric acid to L-malate. In this study, we examined the cultural conditions which affect to the fumarate metabolism by 3 strains of Lactobacillus delbrueckii.

【Methods】

We determined the quantity of organic acids in the culture fluid. We filtrated bacterial bodies and measure the filtrate with high-performance liquid chromatography. The degree of bacterial growth was evaluated by optical density with 660 nm.

【Results】

Bacterial growth was promoted by applying fumaric acid to mediums based on the examination about medium compositions. We also examined the effect of metal-ion to the fumarate metabolic potential. The fumarate metabolic potential was enhanced in the culture added Mg2+, but it was suppressed in the culture added Cu2+. The transformation from fumaric acid to L-malate among these 3 strains associated with their growth and its maturity rate did not change either in static culture or shaking culture. 

Journal of Food Science and Technology. 40, 316-322 (1993)

【Objective】

L-malate is one kind of organic acid which microorganisms produce. It plays an important role not only for fermented foods but also for the compounds to add flavor and acidity to juice and soft drinks. We compared the capabilities of transforming fumaric acid to L-malate among various strains of lactic acid bacteria.

【Methods】

We determined the production of L-malate by the enzymatic method in the reaction mixtures which consisted of the suspensions containing each sample strain and fumaric acid. The optimal pH, incubation temperature and sodium chloride concentration were also examined.

【Results】

Many strains that have a great L-malate formation potential belonged to Lactobacillus. Optimal pH at the transformation from fumaric acid to L-malate among Lactobacillus delbrueckii subsp. lactis 1135 and Lactobacillus delbrueckii subsp.bulgaricus 7235 was pH 7 and pH 6. Both strains demonstrated great L-malate formation properties in the range of 30 to 45 degree C. The highest L-malate production of lactis 1135 and bulgaricus 7235 was measured when the sodium chloride concentration was 10% and 3%.