Ethiopian traditional soured milk ‘Ergo’ is made by natural fermentation in a container previously seasoned by inverting over a piece of smoking olive wood. The lactic acid bacteria present in 3 samples of Ergo were isolated and some of their biochemical characteristics were studied.
　All strains of lactococci produced L-lactic acid, and were determined as Lactococcus garvieae and Lactococcus lactis subsp. lactis from other various taxonomic assays. The lactobacilli isolated produced D-lactic acid and were regarded as only one species, however, this strain was different from all type strains belonging to the genus Lactobacillus.
　Since these three kinds of lactic acid bacteria were isolated from each different sample, it is indicated that there is some deal of variation between the samples with respect to the development of microorganisms during the fermentation of Ergo.
　Although the three strains of lactic acid bacteria did not inactivate the growth of Escherichia coli RB, Staphylococcus aureus IAM 1011, Lactococcus lactis subsp. lactis NIAI 527 and Lactobacillus bulgaricus 7235, the growth of Streptococcus thermophilus NIAI 510 was inactivated.

View full abstract

　A fumarate hydratase (EC 4.2.1.2, known as fumarase) produced by Lactobacillus delbrueckii subsp. bulgaricus 7235 was purified and its characteristics were examined. The purification of fumarase was carried out by protamine sulfate and ammonium sulfate fractionation and by column chromatographies of Mono P, Hi Load and Mono Q.
　The purified enzyme showed 277-fold higher activity than that of cell-free extracts and was observed as a single band by SDS-polyacrylamide gel electrophoresis.
　The purified fumarase was shown to have a molecular weight of 163,000 by gel filtration chromatography. Since the molecular weight of subunit was estimated 52,000 by SDS-PAGE, this enzyme was assumed to be composed of three subunits. The Km value was 15.38 mM for fumarate. Optimal pH was 5.5 whereas optimal temperature was 45℃. The activity was found to be stable between 20 and 45℃ after 30 minutes incubation. Although the activity was inhibited in the presence of Cu²⁺ and Zn²⁺ it was activated by the addition of Al³⁺.

View full abstract

　An antimicrobial substance produced by Lactobacillus amylovorus IMC-1 was found to show bactericidal action against both Pseudomonas fragi IFO 3458 and Bacillus subtilis IFO 3025, and to show bacteriostatic activity against Staphylococcus aureus IAM 1011.
　The addition of the antimicrobial substance in the absence of EDTA did not cause changes in viable counts for Staph. aureus, while it was decreased in the presence of EDTA. It was demonstrated that EDTA enables the antimicrobial substance to permeate the cell wall for access to the target of its bactericidal action. The mortality rate of cells in the presence of the antimicrobial substance was severely decreased at low temperatures, presumably as a result of an increased ordering of the cell structure. Tween 80 stimulated the bactericidal effect of the antimicrobial substance, and it was dose-dependent.

View full abstract

　The current study examined the effect of the Tremella fuciformis berkeley polysaccharide on milk curd formation. It was determined that this polysaccharide could significantly increase the viscosity, hardness, breaking energy and elastic modulus, and decrease the clotting time and syneresis of milk curd. The study of milk curd microstructure established that this polysaccharide could interact with casein micelles, and the interaction between them caused a higher density, three-dimensional network in the milk curd. This network could improve water-holding capacity in the milk curd, and give milk curd thickness to prevent the fracture of curd and wheying-off. Furthermore, it could increase the viscosity, hardness, breaking energy, as well as the elastic modulus and reduce syneresis of the milk curd. It was also determined that these effects had a positive relationship with polysaccharide content in the milk curd.

View full abstract

　An endopeptidase from Lactococcus lactis ssp. lactis IAM 1198 was purified by conventional chromatographic techniques. The molecular weight of the enzyme was estimated to be 95000 by gel filtration and was composed of two hetero subunits, 45 kDa and 52 kDa, respectively. Activity was maximal at pH 6.5–7.0 and 35℃. The enzyme was almost stable at pH values from 6.0 to 7.0 and below 35℃. The michaelis constants of the enzyme for carbobenzoxy-L-phenylalanyl-L-arginine-4-methyl-coumaryl-7-amide and L-arginine 4-methyl-coumaryl-7-amide were 38μM and 25μM, respectively. The enzyme showed both endopeptidase and aminopeptidase activity.

View full abstract