Enumeration of Intestinal Bifidobacteria by Growth on a Semi-selective Medium and GLC Assay of Acetic Acid Production

Prebiotic, Immunomodulating, and Antifatigue Effects of Konjac Oligosaccharide

Irregular and long time work schedules not only makes people feel fatigue, but also brings great risks of diseases, due to gastrointestinal disorder and immune dysfunction. Therefore, it has positive significance to help challenged people stay energetic and healthy with food supplement. Konjac oligosaccharide has shown various physiological benefits and been recommended in the fortification of functional foods. However, there have been few reports on its application aimed to simultaneously relieve physical fatigue and keep body healthy. In this paper, the potential prebiotic, immunoregulatory, and antifatigue activities of konjac oligosaccharide were evaluated in vitro and in vivo. The results showed that konjac oligosaccharide could promote probiotics growth and short chain fatty acids production in mice cecum. At the concentration of 50 to 200 μg/mL, konjac oligosaccharide could activate murine macrophage RAW 264.7 to secret NO and cytokines of IL-10 and IL-6. Moreover, this oligosaccharide could alleviate physical fatigue by prolonging exhaustive time, improving the level of superoxide dismutases and glutathione peroxidase, increasing the content of blood glucose, and decreasing the content of blood urea nitrogen. The results suggested that konjac oligosaccharide had prebiotic, immunoregulatory, and antifatigue effects, providing its application potential in functional food aimed at people with irregular and long time work.

Isolation and characterization of potential probiotic lactobacilli from pig feces

This study examined four lactobacilli isolated from pig feces. Two hundred lactic acid bacteria strains were obtained from pig feces using selective culture media (with vancomycin and bromocresol green; termed LAMVAB agar). Microscopy, the catalase test, Gram-staining, and RAPD-PCR analysis were used to group the bacteria into 20 related clusters. Phenotypic analysis using the API 50 CH test and genotypic analysis of 16S rDNA sequences identified these clusters as representing single strains of each of Lactobacillus fermentum, Lactobacillus salivarius, Lactobacillus plantarum, and Lactobacillus reuteri. Bacterial survival under the conditions of low pH (2.0) and high concentration (5.0%, w/v) of bile salt was much better than that of the reference strain (Lactobacillus acidophilus ATCC 33199). The isolated bacteria were quite capable of inhibiting the growth of two pathogens, Escherichia coli K88 and Salmonella typhimurium. The high acid-resistance, bile resistance and antagonism against pathogens, suggest that the four lactic acid bacteria isolated from pig feces could prove useful as piglet probiotics.

Media for the isolation and enumeration of bifidobacteria in dairy products

Bifidobacteria are commonly used for the production of fermented milks, alone or in combination with other lactic acid bacteria. Bifidobacteria populations in fermented milks should be over 10(6) bifidobacteria/g at the time of consumption of strain added to the product. Hence, rapid and reliable methods are needed to routinely determine the initial inoculum and to estimate the storage time period bifidobacteria remain viable. Plate count methods are still preferable for quality control measurements in dairy products. It is, therefore, necessary to have a medium that selectively promotes the growth of bifidobacteria, whereas other bacteria are suppressed. The present paper is an overview of media and methods including summaries of published comparisons between different selective media. Culture media for bifidobacteria may be divided into basal, elective, differential and selective culture medium. Non-selective media are useful for routine enumeration of bifidobacteria when present in non-fermented milks. Reinforced Clostridial Agar and De Man Rogosa Sharpe (MRS) supplemented with cysteine and agar available commercially are the media of choice for industrial quality control laboratories. Several media for selective or differential isolation have been described for enumeration of bifidobacteria from other lactic acid bacteria. From the large number of selective media available, it can be concluded that there is no standard medium for the detection of bifidobacteria. However, Columbia agar base media supplemented with lithium chloride and sodium propionate and MRS medium supplemented with neomycin, paromomycin, nalidixic acid and lithium chloride can be recommended for selective enumeration of bifidobacteria in dairy products.

Comparison of media for the detection of bifidobacteria, lactobacilli and total anaerobes from faecal samples

The interest in functional foods, probiotics and prebiotics requires a proper method to determine specific bacterial groups in the intestinal flora, especially bifidobacteria and lactobacilli. Three media for lactobacilli (MRS, Rogosa, LAMVAB), three media for bifidobacteria (RB, NPNL, Beerens medium) and nine media for total anaerobes have been tested for selectivity and recovery. For total anaerobes Faecal Reinforced Clostridial Agar (FRCA) showed the highest cfu/g, followed by Columbia Blood Agar and BHI Blood agar. There were no significant differences between the media tested. Reduced physiological salt solution was found to be the best dilution medium. For bifidobacteria and lactobacilli samples of human faeces, cat faeces and pig ileal contents were used. Bifidobacteria could reliably be determined on all three media tested in human faeces, but not on pig ileal contents or cat faeces. Absolute counts were highest in human samples. No lactobacilli could be isolated on MRS in either sample, none of the colonies in the countable plates were lactobacilli. For Rogosa over 90% of the colony types observed in human samples were not lactobacilli. For cat faeces this was 58%, but no false positives were observed in the pig ileal samples. For LAMVAB the percentages of false positive colony types were 9, 14 and 0% for human, cat and pig samples. It can be concluded that for bifidobacteria RB and Beerens medium show comparable results, and can be used to quantify bifidobacteria in human faeces, but none of the media tested is suitable for reliably counting bifidobacteria from pig and cat samples. For lactobacilli LAMVAB shows the highest sensitivity.

Factors influencing the presence of faecal lactobacilli in early infancy

The faecal flora of 46 preterm infants and 52 born at full term was studied at 10 days of age; 46 born at full term and 37 preterm infants were also studied at 30 days. Viable counts of coliforms, lactobacilli, and bifidobacteria were made; gas liquid chromatography was used to identify the anaerobes. Lactobacilli, but not bifidobacteria, were found in high counts in the stools of most of the infants born at full term by 30 days of age. The mode of delivery, but not the method of feeding, had a significant influence on early colonisation. A selective deficiency of lactobacilli compared with coliform organisms was found in preterm infants. Previous treatment with antibiotics and being nursed in an incubator were also significantly associated with a lower rate of early colonisation with lactobacilli. Our findings indicate that lactobacilli may be an important part of the normal stool flora in early infancy, and that modern methods of neonatal care are associated with delayed or deficient colonisation.