In vitro fermentation of polysaccharides of rye,wheat and oat brans and inulin by human faecal bacteria

The in vitro fermentabilities of rye, wheat and oat brans and of a commercial fibre preparation, inulin, were compared. The brans were first digested enzymatically to remove starch and protein. The digested brans and inulin were then fermented with human faecal inoculum. The progress of fermentation was studied by following the consumption of carbohydrates and the production of short‐chain fatty acids and gases. Inulin, a short fructose polymer, was consumed significantly faster than the more complex carbohydrates of cereal brans. Carbohydrates of oat bran (rich in β‐glucan) were consumed at a higher rate than those of rye and wheat brans (rich in arabinoxylan). In all brans, glucose was consumed faster than the other main sugars, arabinose and xylose, and arabinose was degraded only slightly. The total production of short‐chain fatty acids was slightly higher with oat bran than with rye and wheat brans and inulin. In the fermentation of inulin, relatively more butyric acid and less propionic acid were produced than in the fermentation of brans. The decrease in pH was also greater in the case of inulin. Wheat bran led to a slightly slower gas formation than rye and oat brans. Formation of gases was fastest and greatest in the case of inulin. In conclusion, rye, wheat and oat brans were fermented in a rather similar way. Fermentation of the brans was different from that of inulin. Cereal brans might serve as a more balanced source of dietary fibre supplement than gas‐producing, readily fermentable polysaccharides such as inulin. © 2000 Society of Chemical Industry     

Degradation of cell wall material of apple and wheat bran by human faecal bacteria in vitro

The effect of the structures of plant cell walls and their component polymers on the degradability of dietary fibre by bacteria of the human colon was investigated by inoculating culture media containing cell wall materials of apple and wheat bran with slurries of human faeces which were then incubated for periods of up to 72 h. In the apple substrates the amounts of pectic polysaccharides were extensively depleted after 12 h, and after 24 h over 90% of the initial carbohydrate had been degraded. Material which remained after incubation was probably comprised of highly branched fragments of rhamnogalacturonans, cross-linked by phenolics and proteins, highly branched fragments of cross-linked xyloglucans, and degraded cellulose. In wheat bran the aleurone layer was preferentially degraded, but the glucuronoarabinoxylans, which were cross-linked by phenolic groups, and the lignified outer layers of the bran were very resistant to attack. Bacteria adhered mainly to the broken or damaged surfaces of the plant cell walls, and in the more resistant tissues only penetrated the intercellular regions.     

Effect of autoclaving sugar-beet fibre on its physico-chemical properties and its in-vitro degradation by human faecal bacteria

The effect of structure and properties of sugar-beet fibre on its degradability by human faecal bacteria was investigated by an in-vitro fermentation test. The composition and physico-chemical properties of sugar-beet fibre were changed by autoclaving. Autoclaving at 122°C and 136°C for I h increased the solubility mainly of pectins and arabinans and caused increased swelling. The form of the fibre influenced the water-binding capacity, the ionic form giving lowest values. Increasing the ionic strength of the medium reduced the water-binding capacity, especially for the raw fibres and fibres autoclaved at 122°C. The composition of the fibre did not entirely explain these differences and the three-dimensional arrangement of the different polymers in the cell wall was apparently involved. Galacturonic acid and arabinose were extensively depleted by human faecal bacteria and after 24h more than 80% of the initial carbohydrates had been degraded. However, the time course measurement of residual polysaccharides, production of short-chain fatty acids and values of pH showed differences in the rate of fermentation; the presence of solubilised material stimulated bacterial proliferation. The removal of pectic polysaccharides increased the degradability of cellulose and this fact suggested that accessibility is mainly responsible for the slow attack of cellulose in sugar-beet fibre.     

Effect of glycation of bovine β-lactoglobulin with galactooligosaccharides on the growth of human faecal bacteria

The in vitro fermentation selectivity of purified galactooligosaccharides (GOS) after their conjugation with bovine β-lactoglobulin (β-LG) via the Maillard reaction and a subsequent simulated gastrointestinal digestion was evaluated. Changes in human faecal bacterial populations, lactic acid and short-chain fatty acids after 10 h and 24 h of fermentation of the digested β-LG:GOS conjugates revealed that this mixture of glycated peptides had a similar bifidogenic activity to the unconjugated GOS. These findings could open up new applications for Maillard reaction products in the functional foods field.     

Evaluation of the prebiotic potential of five kiwifruit cultivars after simulated gastrointestinal digestion and fermentation with human faecal bacteria

We studied the in vitro prebiotic potential of five different cultivars of kiwifruit including the green‐fleshed ‘Hayward’ and ‘Zesh004’ and the gold‐fleshed ‘Hort16A’, ‘Zesy002’ and ‘Zesy003’. The kiwifruit (25 g fresh weight equivalent) were subjected to simulated gastrointestinal digestion before fermentation for 16 h with faecal microbiota from ten individual donors. Microbial metabolites including lactate were quantified while changes in microbiome composition were determined by 16S rRNA sequencing. Lactate concentrations were highest with ‘Hayward’ (P = 0.01) and correlated with the amount of the kiwifruit fibre and polyphenols, chlorogenic acid and cryptochlorogenic acid. All the kiwifruit behaved similar to inulin in increasing the relative abundance of Bifidobacterium (P < 0.001), but unlike inulin, significantly (P < 0.001) increased the abundances of Ruminococcaceae and decreased Bacteroides. In comparison with inulin, the green‐fleshed kiwifruit selectively increased Lachnospira (P = 0.008) while the gold‐fleshed kiwi fruit increased Akkermansia (P < 0.001). These data suggest that the fibre and polyphenol content of the kiwifruit play a role in modulating gut microbial metabolism. Further clinical studies with these kiwifruit cultivars are required to confirm the potential prebiotic benefits that may be achieved by normal dietary intervention.     

Nondigestible carbohydrates,butyrate, and butyrate-producing bacteria

Abstract

Nondigestible carbohydrates (NDCs) are fermentation substrates in the colon after escaping digestion in the upper gastrointestinal tract. Among NDCs, resistant starch is not hydrolyzed by pancreatic amylases but can be degraded by enzymes produced by large intestinal bacteria, including clostridia, bacteroides, and bifidobacteria. Nonstarch polysaccharides, such as pectin, guar gum, alginate, arabinoxylan, and inulin fructans, and nondigestible oligosaccharides and their derivatives, can also be fermented by beneficial bacteria in the large intestine. Butyrate is one of the most important metabolites produced through gastrointestinal microbial fermentation and functions as a major energy source for colonocytes by directly affecting the growth and differentiation of colonocytes. Moreover, butyrate has various physiological effects, including enhancement of intestinal barrier function and mucosal immunity. In this review, several representative NDCs are introduced, and their chemical components, structures, and physiological functions, including promotion of the proliferation of butyrate-producing bacteria and enhancement of butyrate production, are discussed. We also describe the strategies for achieving directional accumulation of colonic butyrate based on endogenous generation mechanisms.     

Histamine production by bacilli bacteria, acetic bacteria and yeast isolated from fruit wines

Eleven red wines imported from foreign country and 40 domestic fruit wines, including 15 red wines, 4 white wines, 7 plum wines, and 14 other fruit wines, sold in the supermarkets in Taiwan were purchased and tested to determine the occurrence of biogenic amines and histamine-forming bacteria. The levels of pH, total soluble solids (TSS), titratable acidity (TA), reducing sugar (RS), total sugar (TS), sulphites, methanol (milligram per liter of pure ethanol), ethanol and Pb in all samples ranged from 3.0 to 4.1, 6.8 to 24.4 °Brix, 0.3 to 1.7 g/100 mL, 0.2 to 17.6 g/100 mL, 1.6 to 28.4 g/100 mL, <2 to 260.5 mg/L, <1 to 2559 mg/L, 5.0 to 15.6 g/100 mL and <1 to 46.2 μg/L, respectively. The levels of TSS, TA, RS, and TS in plum wine samples were significantly higher than those of the other wines samples, whereas the pH value in plum wine samples was lower than that of the other wines samples. The average content for each of the nine biogenic amines in all samples was less than 5.2 mg/L. However, higher levels of histamine and spermine were detected in domestic fruit wine samples than the imported red wine samples. Five histamine-forming isolates isolated from domestic red wine and jackfruit wine, capable of producing 13.0 mg/L to 69.1 mg/L of histamine in trypticase soy broth (TSB) supplemented with 2 g/100 mL l-histidine (TSBH) or MRS broth supplemented with 2 g/100 mL l-histidine (MRSH), were identified as Bacillus pumilus (one strain), Bacillus sp. (two strains) and Acetobacter pasteurianus (one strain) by 16S rDNA sequencing with PCR amplification, and Zygoascus hellenicus var. hellenicus (one strain) by internal transcribed spacer sequencing with PCR amplification. To our knowledge, this is the first report to demonstrate the occurrence of histamine-forming bacilli bacteria, acetic bacteria and yeast in fruit wine.     

盐渍青菜的细菌菌群结构DGGE分析及产酸细菌分离鉴定

采用变性梯度凝胶电泳技术(denatured gradient gel electrophoresis,DGGE)对不同盐渍青菜样品的细菌菌群结构进行了分析。对优势条带测序分析表明,盐渍青菜中主要的优势细菌是乳杆菌属(Lactobacillus)、魏斯氏菌属(Weissella)、糖多孢菌属(Saccharopolyspora)、短芽孢杆菌属(Brevibacillus)细菌。在腌渍初期,海源菌属(Idiomarina)与海洋杆菌属(Marinobacter)细菌较丰富,在腌渍后期明显减少。乳杆菌属细菌在腌渍14、26个月的青菜中含量丰富,在腌渍2个月的青菜中含量较少。通过分离培养技术从盐渍青菜中分离获得23株产酸细菌,通过16S rDNA序列分析初步确定戊糖乳杆菌(Pediococcus pentosaceus)8株,枯草芽孢杆菌(Bacillus subtilis)与植物乳杆菌(Lactobacillus plantarum)各5株,解淀粉芽孢杆菌(Bacillus amyloliquefaciens)2株,溶血性葡萄球菌(Staphylococcus hominis)、解淀粉芽孢杆菌植物亚种(Bacillus amyloliquefaciens subsp.plantarum)、短乳杆菌(Lactobacillus brevis)各1株。DGGE操作简便,能够较好地反映盐渍青菜的细菌菌群变化,在盐渍青菜的细菌菌群结构分析中具有独特的优势。分离获得的产酸细菌可为盐渍工艺改进提供菌种资源。     

低聚壳聚糖对断奶仔猪血清生化指标、抗氧化性能和粪便微生物的影响

研究在断奶仔猪饲粮中添加不同水平的低聚壳聚糖对其血清生化指标、抗氧化性能及粪便菌群的影响.结果显示:与未添加低聚壳聚糖组相比,低聚壳聚糖组断奶仔猪血清总蛋白、白蛋白、球蛋白、总胆固醇和低密度脂蛋白胆回醇差异不显著(P＞0.05);100mg/kg低聚壳聚糖组的谷草转氨酶活性极显著提高(P＜0.01),碱性磷酸酶活性极显著降低(P＜0.01);50、100mg/kg低聚壳聚糖组过氧化氢酶活性提高显著(P＜0.05);低聚壳聚糖对血清中的三碘甲状腺原氨酸、甲状腺素均有提高趋势,其中添加25 mg/kg可显著提高血清中生长激素含量(P＜0.05);低聚壳聚糖组断奶仔猪粪便中大肠杆菌、乳酸杆菌数量均呈下降趋势,其中添加50 mg/kg低聚壳聚糖可显著降低大肠杆菌的数量(P＜0.05).低聚壳聚糖适宜的添加水平为50 mg/kg.     

葡萄抑菌附生细菌筛选鉴定及其结构表征

以夏黑葡萄为研究对象,利用平板划线法分离纯化培养得到附生细菌,通过提取基因组DNA、PCR扩增16S rDNA、基因序列测序,构建系统发育树,进行聚类分析,结合形态学观察,确定菌种的种属地位。在此基础上,以抑菌活性为指标,筛选具有抑菌活性的附生细菌。将筛选到的目标株菌发酵后,采用溶剂萃取得到发酵粗提物,经过电喷雾(electrospray ionization mass spectrometry,ESI-MS)对发酵产物进行分析,初步确定发酵产物的结构。共从夏黑葡萄中分离鉴定了9株附生细菌,其中BDG-5和BDD-2具有显著的抗菌活性,分别为副假单胞菌(Pseudomonas paralactis)和贝莱斯芽孢杆菌(Bacillus velezensis),ESI-MS分析表明,P.paralactis发酵产物中含有环脂肽surfactin和iturin C,B.velezensis可产生脂肽surfactin、iturin A和bacillomycin D,它们是抑菌活性的主要物质。     

乳酸利用菌的筛选、应用及鉴定

以大曲和酒醅为筛选源,采用Lu-Ye选择性培养基进行筛选。通过平板初筛、静置发酵、模拟白酒工艺发酵,筛选出2株降乳酸能力较强的菌株,其在液体静置发酵和模拟发酵情况下,降乳率分别为87.58%,25.97%和98.51%,38.54%。同时采用16S rRNA序列测定和生理生化测定,初步鉴定为解淀粉芽孢杆菌和枯草芽孢杆菌。     

α-淀粉酶产生菌的分离、筛选及鉴定

通过富集培养、平板筛选、摇瓶复筛从40 ℃的温泉底泥中分离筛选出一株产α-淀粉酶菌株，通过菌株的生理生化试验、16S rRNA基因序列遗传分析对该菌株进行鉴定。结果表明，菌株FA4被鉴定为苏云芽孢杆菌（Bacillus thuringiensis），该菌株具有较强的热稳定性，在55 ℃下仍能生长。     

Algae,bacteria, and yeasts as food or feed

The use of algae, bacteria, and yeasts as food for man or feed for animals has been the subject of considerable discussion in both the scientific and technological literature and in the popular press in recent years. This interest has arisen largely as a result of the need for additional food supplies in chronic food‐shortage areas of the world and for food for life‐support of astronauts on extended space missions. We direct out attention here to the most recent literature and attempt to analyze the current status of the use of these microorganisms for either food or feed with projections to possible applications in the future.     

Prevalence of Clostridium botulinum types B,E and F in faecal samples from Swedish cattle

Faeces were collected from 60 cows at three slaughterhouses situated in southern and central Sweden. The faecal samples were collected during two sampling periods over the year, summer and winter. All samples were analysed for the presence of Clostridium botulinum spores, according to a combined selection and enrichment PCR procedure. One PCR assay was specific for part of the type B neurotoxin gene, while the other assay was specific for both type E and F neurotoxin genes. The prevalence of C. botulinum in Swedish cattle was established to be 73% for non-proteolytic type B and less than 5% for types E and F. Twenty-eight (64%) of the positive faecal samples had a spore load of less than 4 spores/g. Statistical analysis (ANOVA) showed that seasonal variation (summer and winter) had a significant effect on the prevalence of C. botulinum type B in cattle, whereas the effect of geographical location of rearing of the cattle (southern and central Sweden) was less significant.     

Populations, types and biochemical activities of aerobic bacteria and lactic acid bacteria from the air of cheese factories

This investigation was carried out in order to identify the airborne bacteria in the processing rooms of two creameries that make, mainly, feta cheese and study some of their biochemical activities. Our results suggest that the numbers of airborne micro-organisms may differ between plants, and the same was observed with the predominant types. The bacteria isolated were primarily Gram-positive, catalase-negative cocci, micrococci and bacilli. The predominant lactic microflora were lactococci and mesophilic lactobacilli, commonly found in feta and other traditional Greek cheeses. A significant number of aerobic bacteria could grow at 4°C and in 6.5% NaCl. In addition, both aerobic and lactic acid bacteria (LAB) exhibited acidifying and proteolytic activities. Slow- and medium-acidification ability of LAB strains were found. There was also a tendency of the strains to preferentially degrade αs-casein. The amounts of amino acids accumulated in the milk were strain dependent. Therefore, there is a possibility that airborne bacteria contaminating cheese milk in the open vats may multiply and contribute to the ripening changes in the cheese.     

Acid, bile, and heat tolerance of free and microencapsulated probiotic bacteria

ABSTRACT:  Eight strains of probiotic bacteria, including Lactobacillus rhamnosus , Bifidobacterium longum, L. salivarius, L. plantarum , L. acidophilus , L. paracasei , B. lactis type Bl-O4, and B. lactis type Bi-07, were studied for their acid, bile, and heat tolerance. Microencapsulation in alginate matrix was used to enhance survival of the bacteria in acid and bile as well as a brief exposure to heat. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested using HCl in MRS broth over a 2-h incubation period. Bile tolerance was tested using 2 types of bile salts, oxgall and taurocholic acid, over an 8-h incubation period. Heat tolerance was tested by exposing the probiotic organisms to 65 °C for up to 1 h. Results indicated microencapsulated probiotic bacteria survived better ( P < 0.05) than free probiotic bacteria in MRS containing HCl. When free probiotic bacteria were exposed to oxgall, viability was reduced by 6.51-log CFU/mL, whereas only 3.36-log CFU/mL was lost in microencapsulated strains. At 30 min of heat treatment, microencapsulated probiotic bacteria survived with an average loss of only 4.17-log CFU/mL, compared to 6.74-log CFU/mL loss with free probiotic bacteria. However, after 1 h of heating both free and microencapsulated probiotic strains showed similar losses in viability. Overall microencapsulation improved the survival of probiotic bacteria when exposed to acidic conditions, bile salts, and mild heat treatment.     

Hull-less barley for swine: ileal and faecal digestibility of proximate nutrients,amino acids and non-starch polysaccharides

The nutritive value of three hull-less barley cultivars (Condor, Falcon and CDC Buck) were evaluated. The samples were analysed for proximate composition, amino acids and non-starch polysaccharides (NSP). Wheat and normal barley were used for comparison. Apparent digestibilities were determined with eight cannulated pigs. The diets were formulated to have all energy and protein supplied by the cereals. Compared to normal barley, hull-less barley has higher contents of protein and amino-acids, and lower levels of fibre components. The levels of several essential amino acids in hull-less barley are higher than in wheat. No obvious differences in NSP composition were observed, but the hull-less barley contained considerably higher levels of β-glucan compared to hulled barley and wheat. In digestion trials the piglets did not accept the diet in which conventional barley was formulated as the only energy and protein source, whereas hull-less barleys were well consumed. The results showed that, in the order of Condor, Falcon, CDC Buck and wheat, the overall tract digestibilities of intake energy were 83·1, 80·3, 83·2 and 82·9%, and of protein were 72·6, 69·5, 76·5 and 77·6%, respectively. The averages of apparent ileal amino acid digestibility were 56·5, 58·4, 65·3 and 65·4%, respectively. Hull-less barleys showed 20–37% ileal digestibility of total NSP. This study provides digestibility coefficients of hull-less barleys, and it is concluded that the digestibility of hull-less barley is comparable to wheat and superior to hulled barley in terms of nutrient composition and acceptability. © 1998 SCI.