刺梨发酵乳的制备及其理化性质比较

刺梨含有丰富的多糖和维生素C 等营养成分以及超氧化物歧化酶（SOD）,具有降低慢性疾病风险及发病率的潜力。该研究选用保加利亚乳杆菌德氏乳杆菌DMLD-H1（Lactobacillus delbrueckii DMLD-H1,简称H1）和嗜热链球菌DMST-H2（Streptococcus thermophilus DMST-H2,简称H2）为发酵剂菌株,通过优化菌种比例、接种量和刺梨汁添加量,确定刺梨发酵乳最佳发酵工艺,并与商业菌种发酵的发酵乳的各项理化性质进行比较。实验表明,最佳的刺梨发酵乳发酵条件为：菌种比例为H1:H2=1:2,接种量为1.0×107 CFU/mL,刺梨添加量为0.06 g/mL。在此条件下发酵所得的刺梨发酵乳pH值为4.47,酸度为76.78 °T,持水力为32.94%,其中分离出11种挥发性物质,蛋白质相对分子质量主要分布在22~38 ku,后酸化4 周后发酵乳的pH值降低至3.89,活菌数含量为1.1×108 CFU/mL。对比商业发酵乳发现,刺梨发酵乳能够抑制发酵乳的后酸化作用,提高持水力,以及提升发酵乳中的酪蛋白含量;然而,刺梨可能会影响发酵乳中原本的风味物质。该研究为一种新型的刺梨发酵乳的开发提供理论依据,为新型功能性发酵乳的研发提供参考。     

hs-3乳酸菌发酵研究

hs-3菌摇瓶发酵培养过程中,适宜培养时间为16h。研究结果表明,接种量、摇瓶转速、装液量对培养后活菌数及胞外多糖产量都有影响。进一步正交实验得出,摇瓶转速为显著性影响因素,摇瓶培养的适宜工艺组合为:转速60r/min,接种量3%,装液量250mL(500mL三角瓶),通过10L发酵罐小试,hs-3菌活菌数最大为1.12×109cfu/mL,胞外多糖最大产量819mg/L,和摇瓶培养基本一致。     

Androgens Upregulate Pathogen-Induced Placental Innate Immune Response

Group B Streptococcus (GBS) is a leading cause of placental infection, termed chorioamnionitis. Chorioamnionitis is associated with an increased risk of neurobehavioral impairments, such as autism spectrum disorders, which are more prominent in males than in female offspring. In a pre-clinical model of chorioamnionitis, a greater inflammatory response was observed in placenta associated with male rather than female fetuses, correlating with the severity of subsequent neurobehavioral impairments. The reason for this sex difference is not understood. Our hypothesis is that androgens upregulate the placental innate immune response in male fetuses. Lewis dams were injected daily from gestational day (G) 18 to 21 with corn oil (vehicle) or an androgen receptor antagonist (flutamide). On G 19, dams were injected with saline (control) or GBS. Maternal, fetal sera and placentas were collected for protein assays and in situ analyses. Our results showed that while flutamide alone had no effect, a decrease in placental concentration of pro-inflammatory cytokines and infiltration of polymorphonuclear cells was observed in flutamide/infected compared to vehicle/infected groups. These results show that androgens upregulate the placental innate immune response and thus may contribute to the skewed sex ratio towards males observed in several developmental impairments resulting from perinatal infection/inflammation.     

Safety aspects, genetic diversity and technological characterisation of wild-type Streptococcus thermophilus strains isolated from north Italian traditional cheeses

Antibiotic susceptibility, antimicrobial activity, genotypic and technological properties of 52 Streptococcus thermophilus isolates, collected from four north Italian traditional cheeses, was investigated. RAPD-PCR, was used to study genetic variability and distinguish closely related strains; the results showed a high degree of heterogeneity among isolates. With regard to technological properties, after 6 h of incubation in milk 25% of the streptococcal strains could be defined as fast acid producers, while after 24 h the majority of isolates (79%) displayed only weak acidification activity. Reduction activity was generally low; in fact, none of these S. thermophilus strains showed a Eh < −102 mV). All the studied S. thermophilus were susceptible to ciprofloxacin, levofloxacin, penicillin G, ampicillin, mupirocin, nitrofurantoin, quinupristin/dalfopristin and rifampicin. Nine isolates were classified as resistant to tetracycline, 6 to streptomycin, 5 to oxacillin, 3 to erytromycin, 3 to vancomycin and only one to chloramphenicol. PCR-based detection did not identify any of the common genetic determinants for vancomycin (vanA, vanB, vanC1, vanC2, vanC3, vanD, vanE, vanG) or erythromycin (ermB and ermC). The genetic basis of the tetracycline resistance phenotype in these strains was linked to tetS-tetL genes (8 isolates) or the tetM gene (1 isolate), and the integrase element int of the Tn916/Tn1545 family of transposons was negative. Four strains were able to produce antimicrobial compounds against Clostridium tyrobutyricum. The study provides new evidence of the resistance of S. thermophilus to antimicrobial agents, confirming the importance of including an accurate safety assessment of phenotypic/biotechnological data when carrying out strain selection for dairy applications.     

Biochemical composition and storage stability of a yogurt-like product from African yam bean (Sphenostylis stenocarpa)

The biochemical and storage properties of African yam bean ( Sphenostylis stenocarpa ) yoghurt-like product were evaluated. Milk extracted from the bean flour using hot water was supplemented with 4% milk protein concentrate (MPC), 0.15% dairy calcium (DC) and 0.5% gelatine (G) (singly or in combination). The milk was fermented with Streptococcus thermophilus and Lactobacillus delbrueckii spp bulgaricus at 43 °C for 3–5 h. Supplemented African yam bean (AYB) yoghurts had a gel-like consistency unlike the control (unsupplemented) sample. Total solids, protein, fat, ash, lactic acid bacterial count, lightness (L-value) and viscosity were improved by supplementation. Riboflavin and antioxidants were reduced; macroelements and thiamine were increased by 0.71–15.6% and 16.7%, respectively, because of fermentation. The stability of the product during storage at 4 °C was improved by supplementation and stirring. The pH of the supplemented product ranged from 4.45 to 4.54 and microbial counts from 2.6 × 10⁶ to 1.6 × 10⁸ during storage for not more than 3 weeks.     

Sensory evaluation of probiotic Minas fresh cheese with Lactobacillus acidophilus added solely or in co-culture with a thermophilic starter culture

Sensory acceptance of formulations of probiotic Minas fresh cheese was investigated. Cheeses were prepared and supplemented with Lactobacillus acidophilus (T1 – probiotic), Lactobacillus acidophilus + Streptococcus thermophilus (T2 – probiotic + starter) or produced with no addition of cultures (T3 – control). Sensory acceptance tests were performed after 7 and 14 days of storage at 5 °C, using a 9‐point hedonic scale (1 = dislike extremely; 9 = like extremely). After 7 days, no significant difference was detected among cheeses T1, T2 and T3 (P > 0.05). After 14 days, cheeses T1 and T2 presented higher acceptance and differed significantly from cheeses T3. Cheeses T3 presented significant difference between 7 and 14 days of storage (P < 0.05), whereas probiotic cheeses T1 and T2 were stable in the same period (P > 0.05). The addition of L. acidophilus, either solely or in co‐culture with a thermophilic starter culture, resulted in good acceptance of Minas fresh cheese, improving sensory performance of the product during storage.     

18C型肺炎球菌荚膜多糖-TT结合物中多糖片段长度对其免疫原性的影响

目的研究18C型肺炎球菌荚膜多糖-破伤风类毒素(TT)结合物中多糖片段的大小对其免疫原性的影响。方法采取乙酸水解多糖,Sephacryl S-300(XK-50)柱纯化多糖片段,ADH法制备结合物,免疫小鼠,检测血清的ELISA抗体滴度、亲和力以及调理吞噬能力。结果得到重复单位数分别为27、25、19、12、10、9和8的多糖片段。与TT制备的结合物在小鼠体内均能诱导产生IgG型抗体,并存在加强免疫效应,表现出T-细胞依赖型抗体免疫反应。随着链长度的缩短,血清GMT有增加的趋势,但只有8RUPn18C-TT与27RUPn18C-TT组之间差异有显著意义。当吞噬率为50%时,血清的稀释倍数分别为35.10、39.60、45.71、104.71、117.00、145.50和478.60。此趋势与抗体滴度呈正相关,但各组间亲和力差异无显著意义。结论较短多糖片段制备的结合物免疫原性高,血清GMT高,调理吞噬能力也强。     

不同发酵条件下Tween80对 乳酸链球菌SM526产Nisin的影响

以SYS3为发酵培养基,研究了在不同发酵条件下Tween80对乳酸链球菌SM526产Nisin的影响.在自然pH、兼性厌氧发酵条件下,在体积浓度0 1%的范围内,乳链菌肽的活性随Tween80浓度的提高而提高,最适浓度(1%)时,提高幅度为36%;浓度超过1%后, Nisin的活性有所降低.在兼性厌氧条件下通过流加NaOH溶液保持恒定pH为 6.5并添加1%的Tween80进行发酵,同不添加Tween80相比,发酵单位提高了30%.在厌氧条件下恒定pH为6.5并添加1%的Tween80进行发酵,同不添加Tween80相比,发酵单位提高了17%.