丁酸的生理功能研究进展

丁酸是一种重要的短链脂肪酸,是结肠细胞重要的能量来源,可控制细胞增殖,具有多种生理功能。近年来大量研究表明,丁酸有促进肠道发育、维持肠道功能与健康、增强机体免疫性能、抗肿瘤、抗氧化等功能,但目前对于丁酸生理功能的研究多停留在利用动物模型或细胞进行单独研究的阶段。本文从肠道组织功能与健康、物质代谢、免疫功能、肿瘤细胞等几个方面综述了丁酸功能的研究进展,并进行了展望,旨在为丁酸的进一步研究与应用提供思路。     

湛江地区养殖南美白对虾冷藏期间的菌相分析及优势腐败菌的初步鉴定

将湛江地区养殖的南美白对虾在(4±1)℃条件下进行冷藏保鲜,通过细菌形态观察和生理生化实验对冷藏不同时期的细菌组成进行了定性和定量研究,并对优势腐败菌进行了初步鉴定。结果表明:湛江地区养殖的南美白对虾冷藏初期的细菌总数为2.8×104CFU/g,由10个属的细菌组成,其中有6个属为G-,且它们的数量占细菌总数的80%,其中以黄杆菌和气单胞菌的数量最多,分别占细菌总数的33.3%和13.3%;冷藏的第2天为高品质期,细菌总数为5.1×104CFU/g,黄杆菌(30%)和不动杆菌(16.7%)的数量最多,G-的数量增长到86.7%;随着冷藏时间的延长,细菌种类逐渐减少,货架期终点时细菌总数为3.0×106CFU/g,但只分离到8个属的细菌,其中G-占93.4%,气单胞菌和假单胞菌的数量均增加到16.7%,而黄杆菌减少为26.7%,其他种类的G-均有不同程度的增长。冷藏至第6天,细菌总数高达2.4×107CFU/g,虾肉完全腐败变质,从中分离获得的4个属的优势腐败菌均为G-,它们分别是黄杆菌、希瓦氏菌、假单胞菌和气单胞菌,各自所占比例为28.74%、26.44%、21.84%和16.09%。     

Yak-milk-derived exosomes promote proliferation of intestinal epithelial cells in an hypoxic environment

Intestinal epithelial cells (IEC) are an important part of the intestinal barrier. Barrier function was disrupted under hypoxia, but milk-derived exosomes can regulate the intestinal barrier function. However, the mechanisms underlying the association between yak milk exosomes and hypoxia in IEC remain poorly understood. In this follow-up study, we proposed an effective optimization method for purifying yak-milk-derived exosomes. The Western blot analyses indicated that the expression of the proteins of the endosomal sorting complexes required for transport (TSG101), proteins of the tetraspanin family (CD63), and heat shock protein 70 (Hsp-70) proteins from yak-milk-derived exosomes were significantly higher than those in cow-milk-derived exosomes. Flow cytometry analysis showed that yak milk had 3.7 times the number of exosomes compared with cow milk. Moreover, we explored whether yak milk exosomes could facilitate intestinal cell survival under hypoxic conditions in vitro. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide results showed that yak-milk-derived exosomes significantly increased survival of IEC-6 cells with rates of up to 29% for cells incubated in hypoxic conditions for 12 h, compared with those of cow-milk-derived exosomes posttreatment (rates of up to 22% for cells incubated in hypoxic conditions for 12 h). Confocal microscopy revealed that the IEC-6 cells uptake more yak-milk-derived exosomes than cow milk in hypoxic conditions. Furthermore, the Western blot analyses indicated that yak-milk-derived exosomes significantly promote oxygen-sensitive prolyl hydroxylase (PHD)-1 expression and decrease the expression of hypoxia-inducible factor-α and its downstream target vascular endothelial growth factor (VEGF) in the IEC-6 cells. Further, yak-milk-derived exosomes significantly inhibited p53 levels. In conclusion, our findings demonstrate that yak-milk-derived exosomes more effectively activate the hypoxia-inducible factor signaling pathway, thus promoting IEC-6 cell survival, which may result in higher hypoxia tolerance than cow-milk-derived exosomes.     

鱼肉风味淀粉肠的制作和优化研究

通过单因素和正交试验,确定了鱼肉风味淀粉肠的鱼肉香精与马铃薯淀粉、绿豆淀粉的最优配制比例,为企业提供可行性依据,降低生产成本,提高利润,同时为消费者提供物美价廉的产品。     

Pellicle formation,microbial succession and lactic acid utilisation during the aerobic deteriorating process of Sichuan pickle

The pellicles formation, microbial changes and lactic acid utilisation during the aerobic deterioration of Sichuan pickle were discussed in this study. By plate counting, chemical detection and HPLC analysis, the aerobic deterioration of Sichuan pickle was featured by microbial growth, pellicle formation, lactic acid decrease and pH elevation. Bacteria dominated in pellicles and the pellicles present morphological change from smooth to wrinkly along with the aerobic deteriorating process. Nine species of bacteria were identified and responsible for the pellicle formation. Combined with Lactobacillus plantarum, eight pellicle‐forming bacteria were the dominant lactic acid consuming organisms in deteriorating Sichuan pickle. Especially under the harsh acid condition of the early deteriorating period, Lb. plantarum, pellicle‐forming bacteria Bacillus amyloliquefaciens, B. subtilis and Citrobacter freundii participated in the pellicles, utilised lactic acid and increased the brine pH effectively. Sequence analysis of 16S rDNA libraries suggested that the resulting pH of 4.8–5.0 initiated the growth of more undesirable organisms, and the pellicle bacterial diversity changed greatly compared with that in the early deteriorating period. The study indicated the important role of pellicles in the initiation of Sichuan pickle's aerobic deterioration and enhanced our ability to understand and potentially control the aerobic deterioration.     

全谷物体外对肠道菌群影响的研究

选取了5种谷物(燕麦、大麦、全麦、糙米、黑米)和一种精致谷物(大米)为研究对象,在体外研究了其对肠道菌群的影响,并对其成分与肠道菌群发酵前后变化量进行了相关性分析。结果表明,全谷物样品发酵后双歧杆菌数量显著增加,肠杆菌科和梭状芽孢杆菌数量显著下降,除黑米外其他谷物发酵液中乳酸杆菌数量显著增加;发酵后大米中双歧杆菌和乳酸杆菌数量有所下降,肠杆菌科和梭状芽孢杆菌数量显著上升,特别是肠杆菌数量由7.231 g(cfu)/mL增长到8.041 g(cfu)/mL。     

植物乳杆菌ST-Ⅲ对小鼠肠道菌群的调节

以小鼠粪便中的双歧杆菌、乳杆菌、肠杆菌、肠球菌、产气荚膜梭菌数量为检测指标,比较了灌胃含有植物乳杆菌ST-Ⅲ活菌量6×107,6×108,6×109mL-1的脱脂奶液对小鼠肠道菌群的影响。结果表明,植物乳杆菌ST-Ⅲ对小鼠肠道菌群具有一定的调节效果,有效剂量为6×108mL-1。灌胃108mL-1活菌15d,停止灌胃3～5d后仍具有显著效果,5～7d后各项指标菌的量回复到灌胃前水平。     

乳汁中的寡糖及在乳品工业中的应用

母乳中的寡糖大约占总糖的10％，根据其核心结构不同可分为12类，其寡糖组分随哺乳期的变化而改变。母乳中的寡糖具有独特的生理功能，对于婴儿的神经系统发育、预防感染和促进正常的肠道微生物生态形成等非常重要，是保证婴儿健康成长的关键因素．目前用于婴儿乳添加剂的寡糖主要有寡聚果糖和寡聚半乳糖。本文讨论了母乳寡糖的结构、消化吸收、生理作用和在乳品工业中的应用。     

Phenotypic and technological diversity of lactic acid bacteria and staphylococci isolated from traditionally fermented sausages in southern Greece

The physicochemical and microbiological characteristics of spontaneously fermented sausages made by two medium-sized enterprises (MSE) located in southern Greece have been studied. A total of 300 lactic acid bacteria and 300 staphylococcal strains have been isolated and identified by their physiological characteristics. Lactobacillus plantarum strains were found to dominate the lactic acid bacteria microbiota in most of the cases with L. sakei strains prevailing in some of them and L. rhamnosus strains occasionally accompanying the dominant lactic acid bacteria microbiota. On the other hand, S. saprophyticus strains were found to dominate the staphylococcal microbiota in all spontaneously fermented sausages with of S. simulans, S. xylosus, S. gallinarum and S. cohnii cohnii strains being sporadically present. Following the identification, an evaluation of their technological properties, namely proteolytic and lipolytic capacities as well as production of biogenic amines and antimicrobial compounds, took place. None of the lactic acid bacteria and staphylococci was found to possess lipolytic activity whereas a total of 6 lactic acid bacteria and 51 staphylococci strains were found to be able to hydrolyse either the sarcoplasic, myofibrillar or both protein fractions. Furthermore, only one L. sakei strain and 185 staphylococci strains were found to possess decarboxylase activity against lysine, tyrosine, ornithine or histidine. Finally none of the staphylococcal microbiota and 3 lactic acid bacteria strains were found to be able to produce antimicrobial compounds of proteinaceous nature against Listeria monocytogenes.     

Quality attributes of farmed eel (Anguilla anguilla) stored under air, vacuum and modified atmosphere packaging at 0 degrees C

The shelf life of fresh eel in various packaging conditions of atmospheric air, vacuum and modified atmosphere packaging (MAP) (40% CO(2), 30% N(2) and 30% O(2)) at 0 degrees C was investigated. All raw eel samples received acceptable sensory scores during the first 11+/-1 days of storage in atmospheric air, 11+/-1 days of storage in vacuum and finally 18+/-1 days of storage in MAP conditions. Using the microbial quality indicators the shelf life of eel packed in air, vacuum and MAP was estimated to be more than 18, 28 and 34 days, respectively. The main spoilage microorganisms under MAP conditions were lactic acid producing bacteria followed by Shewanella spp., pseudomonads, Enterobacteriaceae and yeasts. Chemical data revealed that pH, ammonia, glucose and lactate examinations might not be useful for monitoring eel quality differences.