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Probiotic properties of bifidobacteria
No full textBifidobacteria are major components of the indigenous bacterial population present in the human gut and are arguably most relevant to the health-promoting properties that have been attributed to elements of this microbiota. They exert a range of beneficial health effects, including the regulation of intestinal microbial homeostasis, the inhibition of pathogens and harmful bacteria that colonize and/or infect the gut mucosa, the modulation of local and systemic immune responses, the repression of procarcinogenic enzymatic activities within the microbiota, the production of vitamins, and the bioconversion of a number of dietary compounds into bioactive molecules. This chapter summarizes the reported health-promoting properties of members of the genus Bifidobacterium and discusses what research is still necessary for an in depth understanding of the probiotic function. In fact, although experimental evidence of the probiotic effectiveness of bifidobacteria has a long history, little information is available on the molecular mechanisms underlying the health-promoting claims, especially on such complex phenomena as anticarcinogenic and anti-inflammatory effects
Candida freyschussii: an oleaginous yeast producing lipids from glycerol
No full textA surplus of glycerol is obtained from biodiesel manufacturing and represents a waste product whose applications are lacking. Thus, the use of glycerol as substrate for fermentation processes yielding valuable products is very attractive. In this study, the utilization of glycerol as a growth substrate for the cultivation of oleaginous yeasts was explored with the aim to produce microbial oils. Forty strains of environmental non-conventional yeasts belonging to 19 different species were screened for the ability to grow on glycerol and produce intracellular lipids in a medium containing an excess of this carbon source (C:N = 48:1). Three strains, belonging to the species Candida freyschussii, Pichia farinosa, and Saccharomyces spencerorum, depleted 40 g/L glycerol within 120 h and produced intracellular lipids. C. freyschussii yielded the highest amounts, lipids accounting for the 33 % of biomass on dry basis. 1H-NMR analysis revealed that the lipid extract did not contain detectable free fatty acids and was composed mostly of triacylglycerols. Lipid composition, determined by GC-MS analysis, was similar to plant oils, and may be optimal feedstock for biodiesel production, being dominated by monounsaturated C16 and C18. As in other oleaginous yeasts, lipid production by C. freyschussii sp. increased with the increase of the C:N ratio of the medium, but growth was inhibited at glycerol concentrations higher than 40 g/L. As a result, lipid production was the highest with 40 g/L glycerol, yielding 4.7 g/L lipids, with a mean volumetric productivity of 0.15 g/L/h. In order to prevent growth inhibition over 40 g/L glycerol and extend the lipogenic phase, different fed-batch strategies were tried. The best performing processes took advantage from the feeding with concentrated media exhibiting the same C:N ratio of the basal medium, leading to very productive high cell density cultures. With the continuous feeding of 20X-concentrated medium, 29 g/L lipids (i.e. the 32 % of biomass) were obtained in 100 h of cultivation, with a mean volumetric productivity of 0.30 g/L/h. The values herein reported are among the highest yield and productivity values ever obtained for fermentative processes exploiting oleaginous fungi to produce lipids from glycerol. Therefore, C. freyschussii could be considered as an interesting microorganism to convert glycerol into microbial oils for biofuel industr
Production of Single Cell Oils from Glycerol By Oleaginous Yeasts
No full textIntroduction: A surplus of crude glycerol is obtained as the
by-product of biodiesel manufacturing and has became a waste
product whose applications are lacking. Thus, the use of crude
glycerol as substrate for fermentation processes yielding valuable
products is attractive. In this study, the utilization of glycerol as a
growth substrate for the cultivation of oleaginous yeasts has been
explored.
Methods: 40 environmental yeasts belonging to 19 different
species were screened for the ability to grow and produce
intracellular lipids at 30 ◦C in a medium containing glycerol
excess (C:N = 48:1). The most promising strain was challenged for
lipid production under increasing C:N ratios, in batch and fedbatch
bioreactor processes. Lipids were extracted from lyophilized
biomass and determined gravimetrically. GC-MS analysis of fatty
acids methyl-esters was performed.
Results: Three out of 40 strains, belonging to the species Candida
freyschussii, Pichia farinosa, and Saccharomyces spencerorum,
depleted 40 g/L glycerol within 120 h and produced intracellular
lipids. C. freyschussii sp. produced the highest amount of lipids,
accounting for the 30% of biomass dry weight and the 8% of glycerol
conversion. C16 and C18 (C18, C18:1, C18:2, and traces of C18:3)
were the most abundant fatty acids, accounting for the 40 and 55%,
respectively, with an unsaturation index of 0.9. Lipid production
was positively affected by glycerol concentration and was the highest
(30% of biomass weight) with 40 g/L glycerol. Since glycerol
inhibited the growth of C. freyschussii sp. above 40 g/L, fed-batch
processwasdeveloped.When50% glycerolwasfed, lipids increased
up to 48% of biomass.
Discussion: This study represents the first proposal of a biotechnological
application of C. freyschussi, a rare non-albicans Candida.
The yeast resulted oleaginous and a good candidate for the production
of single cell oils from glycerol
Folate production by probiotic bacteria.
Full text linkProbiotic bacteria, mostly belonging to the genera Lactobacillus and Bifidobacterium, confer a number of health benefits to the host, including vitamin production. With the aim to produce folate-enriched fermented products and/or develop probiotic supplements that accomplish folate biosynthesis in vivo within the colon, bifidobacteria and lactobacilli have been extensively studied for their capability to produce this vitamin. On the basis of physiological studies and genome analysis, wild-type lactobacilli cannot synthesize folate, generally require it for growth, and provide a negative contribution to folate levels in fermented dairy products. Lactobacillus plantarum constitutes an exception among lactobacilli, since it is capable of folate production in presence of para-aminobenzoic acid (pABA) and deserves to be used in animal trials to validate its ability to produce the vitamin in vivo. On the other hand, several folate-producing strains have been selected within the genus Bifidobacterium, with a great variability in the extent of vitamin released in the medium. Most of them belong to the species B. adolescentis and B. pseudocatenulatum, but few folate producing strains are found in the other species as well. Rats fed a probiotic formulation of folate-producing bifidobacteria exhibited increased plasma folate level, confirming that the vitamin is produced in vivo and absorbed. In a human trial, the same supplement raised folate concentration in feces. The use of folate-producing probiotic strains can be regarded as a new perspective in the specific use of probiotics. They could more efficiently confer protection against inflammation and cancer, both exerting the beneficial effects of probiotics and preventing the folate deficiency that is associated with premalignant changes in the colonic epithelia
Dietary Isoflavones and Intestinal Microbiota: Metabolism and Transformation into Bioactive Compounds
Full text linkEdible plants provide the human with hundreds of non-nutritional phytochemicals which are recognized as beneficial, such as isoflavones. Likewise other polyphenols, isoflavones may undergo extensive transformations during passage through human digestive tract, especially in the colon, where members of the complex commensal microbiota are capable to carry out synergistically a broad range of metabolic transformations affecting the fate and the biological activity of phytochemicals. Diverse bacterial species occurring in the large intestine hydrolyze the glucose conjugated forms of isoflavones, releasing the corresponding aglycones, which may undergo further microbial conversions (especially reductions) giving rise to a wide spectrum of isoflavone-derived compounds. The end-products of microbial transformations are subjected to substantial person-to-person variation, reflecting the impact of the colonic microbiota, since intestinal bacteria may greatly increase or compromise the biological activity of dietary isoflavones. In fact, certain reduction products (e.g. S-equol) possess superior antioxidant and estrogen-like activities, while others are precursors for C-ring cleavage and lead to isoflavone degradation. Extensive research has been performed to characterize the intestinal bacteria which are responsible for isoflavones transformations. In particular, many efforts are being carried out to identify single bacteria that convert the major soy isoflavone daidzein into S-equol, in the perspective to enrich soy products with such a valuable isoflavone-derived metabolite. Besides, diverse bacteria which are capable of deglycosylation, demethylation, and various reduction reactions are increasingly being identified. Nonetheless, only bifidobacteria and lactobacilli, which produce β-glucosidase that hydrolyze isoflavone glycosides into the corresponding aglycones, are currently exploited to improve the biological activity of soymilk
In Vitro Assessment of Prebiotic Activity
No full textBifidogenic effect is a main target for the assessment of prebiotic activity. pH-controlled batch processes of bifidobacteria and fecal microbiota are herein presented. Growth of bifidobacteria, carbohydrate breakdown and consumption, organic acid production, and activity of specific glycosyl hydrolases involved inthe hydrolysis of di-, oligo-, or polysaccharides are exploited to study and compare substrate preference of bifidobacteria for candidate prebiotics
Production of Single Cell Oils by the Cold-Adapted Oleaginous Yeast Rhodotorula glacialis AS 4.7: Effects of the Growth Temperature and the C:N Ratio.
No full textRhodotorula glacialis AS 4.7 is an oleaginous psychrophilic yeast which was isolated
from glacial environments. Despite its origin, the strain abundantly grew and
accumulated lipids up to 20°C. The growth temperature did not influence the yield
coefficients of both biomass and lipids production, but had significant effects on the
growth rate and thus on volumetric productivity of lipid. 15°C were identified as the
optimum temperature for lipid production. As the growth temperature decreased, the
abundance of C18 fatty acids (FA) increased at the expenses of C16 FA and the
unsaturation degree increased as well. In particular, remarkable amounts of linolenic
acid (C18:3 ω-3) were produced at -3°C, accounting for 29% of FA. Lipid production
by R. glacialis AS 4.7 especially occurred in carbon rich media, through a two-stages
process. The first stage resulted in multiplication of cells and finished with the
exhaustion of a nutrient other than the carbon source. During the second stage, the
excess glucose was converted into intracellular storage lipids. The extent of the carbon
excess had major positive effects on lipid production. The lipid content of biomass,
glucose conversion into lipids, lipid concentration, and lipids productivity were all
maximum with 120 g L-1 glucose (68%, 16%, 19 g L-1, and 0.054 g L-1 h-1, respectively).
The results herein reported suggest that R. glacialis AS 4.7 could be considered as an
interesting microorganism for the production of single cell oils and represent the first
proposed biotechnological application for this yeast species
Zinc Uptake by Lactic Acid Bacteria
Full text linkThe study aims to investigate zinc biosorption by strains of lactobacilli and bifidobacteria with a view to exploit them as organic matrixes for zinc dietary supplementation. Sixteen human strains of Lactobacillus and Bifidobacterium were assayed for zinc uptake. The minimum inhibitory concentration of zinc salts differed among the strains, but was never below 15 mmol L−1. When cultured in MRS broth containing 10 mmol L−1 ZnSO4, all the strains were capable of accumulating zinc in the range between 11 and 135 μmol g−1. The highest amount of cell-bound zinc was obtained in L. acidophilus WC 0203. pH-controlled batch cultures of this strain revealed that zinc uptake started in the growth phase, but occurred mostly during the stationary phase. Pasteurized and viable cultures accumulated similar amount of zinc, suggesting that a nonmetabolically mediated mechanism is involved in zinc uptake. These results provide new perspectives on the specific use of probiotics, since L. acidophilus WC 0203 could function as an organic matrix for zinc incorporation. The bioavailability of Lactobacillus-bound zinc deserves to be investigated to provide a future basis for optimization of zinc supplementation or fortification
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