膳食纤维经肠道微生态途径调节脂质代谢作用的研究进展

肠道菌群通过宿主与饮食交互作用在机体的脂质代谢过程中扮演着十分重要的角色。食物中广泛存在的膳食纤维及肠道菌群代谢的产物可选择性地改变肠道菌群组成,进而提高肠道短链脂肪酸水平、降低炎性因子表达水平、影响饥饿禁食诱导因子表达,从而改善机体的脂质代谢水平。膳食纤维这种通过改善肠道菌群组成来调节机体脂质代谢的生物活性作用,为预防和治疗脂质代谢紊乱等相关疾病提供了新的研究思路。本文在查阅文献的基础上,对膳食纤维经肠道微生态途径调节脂质代谢的活性作用及其机制进行了综述。     

明日叶对过度训练致大鼠胃肠功能紊乱影响的研究

研究明日叶对过度训练致大鼠胃肠功能紊乱的作用。建立雄性大鼠过度训练模型,观察过度训练组、补充明日叶组的大鼠肠道主要菌群双歧杆菌、大肠杆菌数量,肠道代谢产物脲酶、β-半乳糖苷酶活性和主要SCFA含量,以及血浆内毒素、组织匀浆SIg A含量的变化。与正常对照组比较,过度训练组双歧杆菌数量及B/E比值显著升高,大肠杆菌数量显著降低;β-半乳糖苷酶活性及主要SCFA乙酸、丁酸含量显著降低,脲酶活性显著升高;组织匀浆SIg A含量显著下降,而血浆内毒素含量显著升高。补充明日叶组各指标与对照组比较均无显著差异。结果表明,明日叶能够从肠道菌群、肠道代谢产物及肠道屏障等几个方面对肠道微生态进行综合调理,促进肠道健康。     

模拟失重条件下水苏糖对大鼠肠道双歧杆菌的影响

研究水苏糖对模拟失重条件下大鼠肠道双歧杆菌的影响。SD大鼠随机分为地面对照组(FC组,饲喂基础饲料)、地面处理组(FTK组,饲喂添加水苏糖的饲料)、尾吊对照组(SC组,饲喂基础饲料)、尾吊处理组(STK组,饲喂添加水苏糖的饲料),试验28 d。采用选择性培养基测定不同时间节点大鼠粪便中双歧杆菌数量。结果表明:与FC组比较, SC组双歧杆菌数量显著减少(P<0.05或P<0.01), FTK组双歧杆菌数量显著增加(P<0.05);与SC组比较,STK组双歧杆菌数量显著增加(P<0.05)。模拟失重导致双歧杆菌生长受到抑制,水苏糖可促进双歧杆菌的增殖,能在一定程度上减轻模拟失重导致的大鼠肠道微生态失调。     

都庆 都庆双歧因子——微生物调节剂

双歧因子顾名思义是促进双歧杆菌增殖的因子。 现代医学证明,双歧杆菌是对人类至关重要的有益菌群,可以说体内双歧杆菌数量的多少是人体健康与否的标志。肠道双歧杆菌增值,具有明显的整肠作用。健康人的肠道内栖息着大量的双歧杆菌,双歧杆菌可抑制有害病原菌的繁殖,调节肠道内菌群数量,继而保持微生态平衡,使病原微生物不能进入人体,防止人体不受细菌感染。国内外调查显示,母乳喂养的婴儿体内双歧杆菌的数量明显高于人工喂养的婴儿,长寿者人体内双歧杆菌数量明显高于正常老人;正常人群体内双歧杆菌数量明显高于病人。     

短双歧杆菌对Aβ;导致的阿尔兹海默症小鼠肠道菌群及代谢物的影响

为分析2株不同来源的短双歧杆菌对脑部微注射Aβ;蛋白导致的阿尔兹海默症小鼠肠道菌群及其代谢物的影响,给小鼠海马区注射Aβ;蛋白建立阿尔兹海默症小鼠模型,连续灌胃6周2株不同来源的短双歧杆菌,收集小鼠粪便,采用Illumina MiSeq高通量测序技术分析菌群的多样性及物种组成,并采用GC-MS技术检测小鼠粪便中短链脂肪酸的含量。菌群多样性分析发现,Aβ;蛋白注射改变了小鼠的菌群多样性及物种结构,灌胃短双歧杆菌可一定程度上改善菌群紊乱。进一步在属水平和种水平分析各组菌群差异,发现灌胃短双歧杆菌MY显著提高了大鼠肠道中产短链脂肪酸菌Coprococcus spp.、Lactobacillus reuteri和Akkermansia muciniphila的相对丰度,且有效调控了肠道内3种短链脂肪酸的水平。短双歧杆菌MY可能通过调节肠道菌群及其代谢物短链脂肪酸的水平缓解小鼠的认知障碍。     

膳食纤维对肥胖相关的肠道微生态的影响

研究发现,肠道微生态的改变与肥胖等代谢性疾病相关。膳食纤维作为饮食的一部分,通过在肠道的作用改变肠道菌群比例及丰度、改善炎症反应、调节肠道激素及脂质代谢来改善肥胖,但膳食纤维在防治肥胖方面的推荐摄入量、种类及与肠道菌群的作用机制还需进一步研究。本文对膳食纤维对肥胖相关的肠道微生态的影响的研究进展进行了综述。     

双歧杆菌RH 菌株不同处理物修复肠道菌群平衡失调的研究

为探讨双歧杆菌RH 菌株对肠道菌群平衡失调的修复功能,本研究通过动物实验,考察双歧杆菌活菌(LB)、菌体破碎物(CE)及发酵上清液(FS)3 种处理物灌胃由抗生素造成的菌群失调模型小鼠后对其肠道内双歧杆菌、乳杆菌、产气荚膜梭菌、肠球菌、肠杆菌和拟杆菌6 大类主要菌群的影响。结果显示：3 种处理物均可使小鼠肠道内双歧杆菌和乳杆菌数量极显著增加(P ＜ 0.01),产气荚膜梭菌和肠球菌数量显著降低(P ＜ 0.05 和P ＜ 0.01),并能使肠杆菌和拟杆菌数量恢复至正常水平,说明该双歧杆菌LB、CE 和FS 均可起到修复、调节小鼠肠道微生态平衡的作用。     

食药用菌多糖经由肠道菌群调节脂质代谢的研究进展

肥胖和高血脂症已成为当今社会严重的公共卫生问题。研究发现食药用菌多糖可以通过促进肠道内益生菌的增殖、抑制有害菌的生长,改善肠道菌群,发挥脂质代谢的调节作用,但目前,其调节脂质代谢的具体机理还未能确定和统一。本文主要围绕食药用菌多糖、肠道菌群、脂质代谢三者之间的相互联系及其作用,以及食药用菌多糖经肠道菌群调节脂质代谢可能的机理,主要包括短链脂肪酸合成途径和减少炎症反应进行了综述,并讨论了食药用菌多糖经肠道菌群调节脂质代谢现有研究的不足之处及未来的发展方向,旨在为食药用菌活性成分的利用及营养功能性食品的研发提供参考。     

低聚糖酸奶饮料增殖肠道有益菌群功能的研究

通过动物试验和人体试食,证实了添加异麦芽低聚糖的酸奶饮料在调节肠道菌群、增殖乳酸杆菌和双歧杆菌等有益菌群有显著作用。     

乳酸菌利用低聚果糖代谢机理的研究进展

低聚果糖能调节肠道菌群,有效地促进双歧杆菌、乳杆菌等乳酸菌在肠道的增殖,然而其代谢机理存在菌种特异性的特点。为了进一步了解乳酸菌代谢低聚果糖的状况,文中分别对乳酸菌负责低聚果糖代谢的转运蛋白、果糖苷酶及其代谢调控方式进行了总结,并对未来的研究方向提出了展望。     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Developmental and population growth rates of phosphine-resistant and -susceptible populations of stored-product insect pests

Phosphine resistance positively contributes towards an individual's fitness under phosphine fumigation. However, phosphine resistance may place resistant individuals at a fitness disadvantage in the absence of this fumigant, which can be exploited to halt or slow down the spread of resistance. This study aimed to determine if there is a fitness cost associated with phosphine resistance in populations of the red flour beetle (Tribolium castaneum (Herbst)), the lesser grain borer (Rhyzopertha dominica (F.)) and the sawtoothed grain beetle (Oryzaephilus surinamensis (L.)). The developmental rate and population growth of phosphine-resistant and -susceptible populations of these three species of stored-product insects were therefore determined under phosphine-free environment. The majority of the phosphine-resistant populations exhibited lower developmental and population growth rates than the susceptible populations indicating that phosphine resistance is associated with fitness cost in all three species, which can potentially compromise the fixation and dispersal of the resistant genotypes. Nonetheless, some phosphine-resistant populations did not show a fitness cost. Therefore, resistance management strategies based on suppression of phosphine use aiming at eventual reestablishment of phosphine susceptibility and subsequent reintroduction of this fumigant will be useful only for insect populations exhibiting a fitness cost associated with phosphine resistance. Therefore recognition of the prevailing phosphine-resistant genotypes in a region is important to direct the management tactics to be adopted.     

Thermal inactivation of Bacillus cereus and Clostridium perfringens vegetative cells and spores in pork luncheon roll

The aim of this study was to design a thermal treatment(s) for pork luncheon roll, which would destroy Bacillus cereus and Clostridium perfringens vegetative cells and spores. B. cereus and C. perfringens vegetative and spore cocktails were used to inoculate luncheon meat. Samples were subjected to different temperatures and removal times. The decimal-reduction times (D-values) were calculated by linear regression analysis (D = -1/slope of a plot of log surviving cells versus time). The log(10) of the resulting D-values were plotted against their corresponding temperatures to calculate (-1/slope of the curve) the thermal resistance (z-values) of each cocktail. The D-values for vegetative cells ranged from 1 min (60 degrees C) to 33.2 min (50 degrees C) for B. cereus and from 0.9 min (65 degrees C) to 16.3 min (55 degrees C) for C. perfringens. The D-values for B. cereus spores ranged from 2.0 min (95 degrees C) to 32.1 min (85 degrees C) and from 2.2 min (100 degrees C) to 34.2 min (90 degrees C) for C. perfringens. The z-values were calculated to be 6.6 and 8.5 degrees C for B. cereus vegetative and spores, respectively, and 7.8 and 8.4 degrees C for C. perfringens vegetative cells and spores, respectively. The D-values of B. cereus and C. perfringens suggest that a mild cook of 70 degrees C for 12s and 1.3 min would achieve a 6 log reduction of B. cereus and C. perfringens vegetative cells, respectively. The equivalent reduction of B. cereus and C. perfringens spores would require the pork luncheon meat to be heated for 36 s at 105 and 110 degrees C, respectively. The results of this study provide the thermal inactivation data necessary to design a cooking protocol for pork luncheon roll that would inactivate B. cereus and C. perfringens vegetative cells and spores. The data may also be used in future risk assessment studies.     

Selection and evaluation of seafood-borne psychrotrophic lactic acid bacteria as inhibitors of pathogenic and spoilage bacteria

In this study, inhibitory psychrotrophic lactic acid bacteria were isolated and investigated for future use in biopreservation of seafood products. Screening of 5575 colonies isolated from various seafood products resulted in the selection of 132 colonies presenting inhibitory properties. Among them, 52 isolates had characteristics of LAB and showed growth at 15 °C but not at 30 °C. The inhibition spectrum of these 52 isolates against 14 target strains (Gram-positive and -negative) showed inhibition of typical seafood spoiling and pathogenic bacteria and enabled the formation of seven interesting clusters. Sequencing of the 16S rRNA gene of a representative isolate from each cluster identified three Leuconostoc gelidum, two Lactococcus piscium, one Lactobacillus fuchuensis and one Carnobacterium alterfunditum. Theses strains did not produce histamine nor tyramine, and showed no particular antibiotic resistance profile. Growth rate as a function of temperature was tested for one L. piscium and one L. gelidum isolate and confirmed their psychrotrophic behavior. One out of seven isolates showed bacteriocin-like activity. The inhibition mechanisms of the other isolates are still unknown but may be due to competition for substrate. Absence of a bacteriocin-like component could be a positive point to gain rapid authorization for food application in France. This collection of LAB is now ready for testing on products.     

Consumer acceptance and steak cutting yields of beef top sirloin and knuckle subprimals

Beef knuckles (n = 150) and center-cut top sirloin butts (n = 150) were used to determine portion-controlled steak cutting yields, palatability characteristics, and consumer acceptance of rectus femoris (RF), vastus lateralis (VL), and gluteus medius (GM) steaks. Steak yields were higher (P < 0.05) for top sirloins than knuckles. Trained sensory panel ratings for overall tenderness, juiciness, and flavor were similar between RF and GM. Consumer panel ratings for tenderness and juiciness were higher (P < 0.05) for GM than RF; however, consumer perceptions of overall like and flavor were similar for GM and RF. Vastus lateralis received lower (P < 0.05) trained panel and consumer ratings for all traits than either RF or GM. Palatability of VL will need improvement to be a viable foodservice offering. Yet, these data suggest that RF would amply substitute for GM in foodservice settings, and that knuckle steak yields would be adequate for foodservice applications.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.     

Efficient transformation of Mesorhizobium huakuii subsp. rengei and Rhizobium species

The transformation of Mesorhizobium huakuii subsp. rengei B3 with either pBBR122 or pKT230 was carried out. We determined the optimal conditions required for transformation by electroporation and obtained up to 10(5) CFU/microg pBBR122. Plasmids prepared from strain B3 yielded higher transformation efficiency than those from various dam or dcm mutant strains of Escherichia coli. This result suggests that a high transformation efficiency is not related to the methylation of plasmid DNA in E. coli. Using the optimal conditions for electroporation, we performed transformation of several species of Rhizobium, Mesorhizobium and Sinorhizobium. All tested strains of these species were transformed with pBBR122. Strains of M. huakuii and R. phaseoli AHU1133 were transformed at high efficiency, whereas transformation efficiencies of Rhizobium sp. NGR234 and S. meliloti strains were less than 2 x 10(3) CFU/microg plasmid DNA.     

Isolation and characterization of psychrotrophs from subterranean environments

Subterranean environments are potential sources for the isolation of novel microorganisms. Water and soil samples were collected at depths ranging from 10 to 1800 meters below the surface, and screening was carried out with aerobic rich and anaerobic minimal media. Two psychrotrophic and three chemoautotrophic strains were isolated. One of the psychrotrophic isolates, designated SN16A, grew at temperatures between -5 and 37 degrees C with optimal growth between 25 and 30 degrees C. The other psychrotroph, designated KB700A, grew between -10 and 30 degrees C. Little difference in growth rate could be observed between 20 and 30 degrees C; however, this strain did not grow at 37 degrees C. KB700A utilized CO2 chemoautotrophically at 30 degrees C, using hydrogen as an energy source. Both strains were characterized biochemically. The complete 16S rRNA sequence of KB700A was 98.7% homologous with that of Pseudomonas marginalis. However, the 16S rRNA of SN16A showed only 95.4% identity at maximum-with the corresponding gene of Arthrobacter globiformis-suggesting that this strain may belong to a novel genus. Both strains exhibited the ability to produce hydrolytic enzymes on plate assays. Our results suggest that subterranean environments are promising sources for the isolation of psychrotrophic microorganisms.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.