Yeast Extract Fermentation Research Articles

Magnetic field assisted arrangement of photocatalytic TiO2 particles on membrane surface to enhance membrane antifouling performance for water treatment

Fabrication of membranes with high antifouling and self-cleaning ability is a long-term pursuit of research community. For this purpose, the current work proposed a strategy to use an external magnetic field to arrange the magnetic TiO2@Ni particles (MNPs) onto the polymeric polyether sulfone (PES) membrane surface. The characterization results clearly indicated that the MNPs were successfully embedded onto the membrane surface instead of uniformly distributing into the membrane bulk. Because of this superficial distribution, the prepared composite membrane exhibited a flux of 871.2 ± 2.9 L·m−2·h−1·bar−1, which was 5 times flux of the pristine PES membrane. Meanwhile, it remained a rejection of 95.85% bovine serum albumin (BSA), which was also better than that of the pristine PES membrane. The cycle filtration experiments verified that the composite membrane possessed promoted antifouling ability for filtrating BSA, yeast extract fermentation (YEF), ammonium alginate (SA) and humic acid (HA) solutions. The antifouling mechanism was analyzed by the total interaction energies (ΔGTotal), which were quantitatively evaluated by using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. Moreover, it was interestingly found that the composite membrane possessed a self-cleaning property under radiation of UV light and sunlight. The optimal membrane after self-cleaning presented flux recovery ratio (FRR) of 75.4%, 99.56%, 92.11% and 98.26% for BSA, YEF, SA and HA solutions, respectively. This work demonstrated a novel way to fabricate membranes with high antifouling and self-cleaning ability for water treatment.

Stimulating effect of protein-rich matter on the biogenic conversion of CO2 to CH4

H2 supply constitutes the bottleneck for the biogenic recycling of CO2 to CH4 via the reduction pathway with H2. Past studies have reported that yeast extract has a significant effect on H2 formation from various types of organic matter. In order to elucidate whether or not less expensive protein-rich matter like protein powder from soybean can be used as substitute for yeast extract, a comparative assessment of biogenic conversion of CO2 to CH4 with H2 supply from the fermentation of yeast extract, protein powder from soybean, and glucose was done using a mixture culture of H2-forming fermentative and H2-using methanogenic microbes. Batch experiment results showed that under H2 limitation conditions, larger amounts of H2 is supplied at the expenses of less CO2 production with yeast extract and protein powder from soybean than with glucose. Protein powder from soybean has been found to have similar stimulating effect on H2 formation to yeast extract. The biogenic conversion of CO2 to CH4 with protein powder from soybean was reflected by a net reduction of CO2 levels. For the first time, it is shown that soybean protein is a potential candidate to stimulate the biogenic recycling of CO2 to CH4 in geological storage sites of CO2.

Acetoanaerobium pronyense sp. nov., an anaerobic alkaliphilic bacterium isolated from a carbonate chimney of the Prony Hydrothermal Field (New Caledonia).

A novel anaerobic bacterial strain, ST07-YET, was isolated from a carbonate chimney of the Prony Hydrothermal Field (PHF) in New Caledonia. Cells were Gram-stain-positive, straight rods (0.7-0.8 × 3.0-5.0 μm) and motile by means of lateral flagella. Strain ST07-YET was mesophilic (optimum 35 °C), moderately alkaliphilic and halotolerant (optimum pH 8.7 and 5 g l- 1 NaCl). Elemental sulfur, sulfate, thiosulfate, sulfite, nitrate and nitrite were not used as terminal electron acceptors. Yeast extract, peptone, tryptone, Casamino acids, crotonate, pyruvate, galactose, maltose, sucrose, ribose, trehalose and glucose were used as carbon sources. Glucose fermentation led to acetate, H2 and CO2 formation. Arginine, serine, histidine, lysine, methionine and cysteine improved growth, but the Stickland reaction was negative for the combinations of amino acids tested. The major metabolic products from yeast extract fermentation were H2, CO2, acetate, butyrate, isobutyrate, isovalerate and propionate. The predominant cellular fatty acids were C16 : 0, C16 : 1cis9, C14 : 0 and C16 : 1cis7 (>5 % of total fatty acids). The G+C content of the genomic DNA was 32.9 mol%. Phylogenetic analysis revealed that strain ST07-YET was most closely related to Clostridium sticklandii DSM 519T and Acetoanaerobium noterae NOT-3T (96.7 % and 96.8 % 16S rRNA gene sequence similarity, respectively). On the basis of phylogenetic, chemotaxonomic and physiological properties, strain ST07-YET is proposed to represent a novel species of the genus Acetoanaerobium (order Clostridiales, phylum Firmicutes) with the name Acetoanaerobium pronyense sp. nov. The type strain is ST07-YET ( = DSM 27512T = JCM 19400T).

Biological Characteristics for Mycelial Growth of <i>Agaricus bisporus</i>

The biological characteristics of Agaricus bisporus mycelia were reported in this study. Biological characteristics of mycelium growth, including carbon source, nitrogen source, carbon-nitrogen ratio, temperature, pH and growth regulators, were investigated. The results indicated that the optimum carbon and nitrogen sources for mycelial growth were glucose and yeast extract fermentation, respectively. The optimum carbon-nitrogen ratio of culture was 20:1～30:1; the optimum temperature was 22～24°C and the optimum pH was 7.0～7.5. Analysis of growth regulators revealed that VC and VB1 were essential in promoting the mycelial growth of white button mushrooms.

Involvement of thermophilic archaea in the biocorrosion of oil pipelines

Two thermophilic archaea, strain PK and strain MG, were isolated from a culture enriched at 80°C from the inner surface material of a hot oil pipeline. Strain PK could ferment complex organic nitrogen sources (e.g. yeast extract, peptone, tryptone) and was able to reduce elemental sulfur (S°), Fe(3+) and Mn(4+) . Phylogenetic analysis revealed that the organism belonged to the order Thermococcales. Incubations of this strain with elemental iron (Fe°) resulted in the abiotic formation of ferrous iron and the accumulation of volatile fatty acids during yeast extract fermentation. The other isolate, strain MG, was a H(2) :CO(2) -utilizing methanogen, phylogenetically affiliated with the genus Methanothermobacter family. Co-cultures of the strains grew as aggregates that produced CH(4) without exogenous H(2) amendment. The co-culture produced the same suite but greater concentrations of fatty acids from yeast extract than did strain PK alone. Thus, the physiological characteristics of organisms both alone and in combination could conceivably contribute to pipeline corrosion. The Thermococcus strain PK could reduce elemental sulfur to sulfide, produce fatty acids and reduce ferric iron. The hydrogenotrophic methanogen strain MG enhanced fatty acid production by fermentative organisms but could not couple the dissolution Fe° with the consumption of water-derived H(2) like other methanogens.

The Fermentation of Trehalose by Yeasts and its Taxonomic Implications

SUMMARY: In the classification of yeasts it is customary to use an infusion of bakers’ yeast as the basal medium for fermentation tests. This extract frequently contains variable amounts of trehalose. A number of yeasts were observed to ferment yeast extract and trehalose. The fermentation of yeast extract is serious from a taxonomic point of view, since it gives the impression of positive fermentation of a sugar which actually may not be fermentable. Dilute yeast autolysate should be used as the basal fermentation medium since during autolysis trehalose is destroyed. The fermentation of yeast extract (without added sugar) is easily observed in Durham tubes by the collection of gas in the inserts, but when Einhorn fermentation tubes are used gas production is seldom apparent. One culture (N-18) isolated from spoiled apricots, and identified as Candida tropicalis showyed adaptive trehalose fermentation. The ability of various yeasts to ferment trehalose was investigated, using 133 cultures, representing twenty genera and seventy-three species. Sixteen species representing seven genera fermented yeast extract and trehalose. The fermentation of trehalose is worthy of consideration as a character for use in differentiating certain species of Candida, and perhaps other yeasts.