酪蛋白水解物对乳酸菌的促生长作用

研究了酪蛋白的木瓜蛋白酶水解物对乳酸菌(嗜热链球菌:保加利亚杆菌=1:1)的促生长作用。通过比较不同水解度的酪蛋白水解物的增值作用,发现酪蛋白经木瓜蛋白酶水解8 h后的水解物具有最强的促进乳酸菌生长作用。本试验进一步考察了该水解物对酸乳乳酸菌代谢产物(乳酸和胞外多糖)的产量及活菌数变化的影响。结果表明木瓜蛋白酶酪蛋白水解液能将乳酸菌乳酸和胞外多糖的产量分别提高33.1%和30.4%。

Physico-chemical and Microbiological Analysis of Algerian Raw Camel＇s Milk and Identification of Predominating Thermophilic Lactic Acid Bacteria

The dromedary camel （Camelus dromedarius） is a significant socioeconomic importance in several arid and semi-arid regions of North Africa and Middle East, and its milk constitutes an important component of human diets in these regions. The camel milk plays a vital role in the food of the Algerian nomads in the Sahara. During February and September, 20 samples of the raw camel＇s milk were taken starting from different livestock of camels from three different Sahariennes regions （Bechar, EI-Bayadh and Naama）. These 20 collected samples were analyzed by physico-chemical and microbiological methods. The results of physicochemical analyze obtained from two hot and cold seasons are respectively the following： T ~C （35.83 and 33.95）, pH （6.36 and 6.49）, density （1.031 and 1.032）, dornic acidity （18.6 and 18.3 ~D）, dry matter （93.4 and 144.8 g/L）, fat contents （30 and 52.1 g/L）, total protein （26.3 and 33.1 g/L） and ashes （7.46 and 8.66 g/L）. The protein profile obtained by electrophoretic analysis （SDS-PAGE） showed that camel milk contains several types of proteins and some have a molecular weight identical to major proteins of the cow＇s milk. The final results showed that camel milk has generally a comparable composition to that of bovine milk. The microbiological analysis, of these samples, detected a significant number of the total microflora, Staphylococcus aureus and total coliforms. The absence of Clostridium and fecal coliforms was observed. Several species of lactic acid bacteria were detected such as Lactococcus lactis subsp, lactis, Lactococcus lactis subsp, lactis biovar, diacetylactis, Weissella cibaria and Enteroccocusfeacalis.

Lactobacilli Improve the Antioxidant Activity in Fermented Coriolus versicolor Extract

Coriolus versicolor has been reported to have biological activities such as anticancer, antibacterial, antibiotics and immunopotentiation. The authors tried to ferment using lactobacilli associated with various biological functions and expected that fermented extract by lactobacilli will be superior to non-fermented extract in antioxidant activity. C. versicolor was extracted with 70% ethanol and then it was fermented by Lactobacillus acidophilus KCTC3164 and Lactobacillus plantarum KCTC3099, respectively. 1,l-dipheny｜-2-picrylhydrazyl （DPPH） scavenging activity, superoxide dismutase （SOD）-like activity and tetrazolium salt 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） assays were performed. DPPH scavenging activity of fermented extract by L. acidophilus was higher than fermented extract by L. plantarum and antioxidant effect of fermented extract was 20%-30% higher than non-fermented extract. SOD-like activity was represented 18% in fermented extract by L. acidophilus, and was 27% in fermented extract by L. plantarum higher than non-fermented extract. As a result, this study suggests that it may need an efficient protocol for dominant bio-physiological activities such as extract volume or appropriate working volume of cultured cell or mixture condition. The fermented C. versicolor extract should provide with useful antioxidant agent in the human skin.

Production of conjugated linoleic acids by Lactobacillus plantarum strains isolated from naturally fermented Chinese pickles

Naturally fermented pickles harbour many lactic acid bacteria （LAB）. Forty-three LAB strains with conjugated linoleic acid （CLA）-producing ability were isolated from three naturally fermented pickle brines. Of these isolates, Ip15 identified as Lactobacillus plantarum by API 50 CHL system and full-length 16S rDNA sequence analysis exhibited the highest CLA-producing ability （26.1% conversion） at 48 h in de Man Rogosa Sharpe （MRS） broth in the presence of 100 IJg/ml of linoleic acid （LA）. Compared to other strains, L. plantarum strain Ip15 showed the highest tolerance upon increased levels of LA in the medium, i.e., up to 600 μg/ml. This strain converted about 25% of LA into CLA isomers [predominantly cis-9, trans-11 CLA （9-CLA） and trans-lO, cis-12 CLA （10-CLA）], of which 75% was 9-CLA. Interestingly, though the conversion rate of LA into CLA by Ip15 remained stable between 100 to 600μg/ml LA levels in the medium, it dropped sharply at 1000 μg/ml. Taken together, the Ip15 strain displayed relatively high LA tolerance with higher conversion rate, which implies that this strain is a valuable candidate for enhancing the CLA content in food-sources like pickles.