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排序方式: 共有96条查询结果,搜索用时 15 毫秒
1.
Batch and continuous production of lactic acid from salt whey using free and immobilized cultures of lactobacilli 总被引:1,自引:0,他引:1
Salt whey permeate was used as a substrate for lactic acid production by different strains of homofermentative lactobacilli. An isolate from Egyptian Cheddar cheese proved to be the most effective lactic acid producer. The salt whey permeate was optimized by addition of yeast extract and minerals to enable exponential growth of organisms. The lactic acid productivity of free and immobilized cells was compared and fermentation conditions were improved. Continuous lactic acid fermentation from salt whey permeate with cells immobilized in agarose beads was successfully carried out in a chemostat with a steady lactic acid concentration of 33.4 mg/ml. 相似文献
2.
3.
Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium. 相似文献
4.
Ahmed Zayed Mariya Kovacheva Kai Muffler Hans‐Werner Breiner Thorsten Stoeck Roland Ulber 《Engineering in Life Science》2019,19(5):363-369
Induction of an axenic filamentous‐like callus growth from the brown algae Fucus vesiculosus is described. Different treatments were investigated in various combinations to develop axenic cultures based on identification of surface symbionts via 18S ribosomal RNA. Moreover, viability was confirmed after such processes by 2,3,5‐triphenyl tetrazolium chloride assay that demonstrated an average viability of 29%, relative to nonsterilized explants. After six weeks of a phototrophic cultivation on artificial sea water‐12‐nitrilotriacetic acid (0.5% w/v agar), a filamentous‐like callus growth was observed, which was identified genetically through its mitochondrial DNA after subculturing. Achievement of confirmed marine callus cultures might enrich old previously established blue biotechnology techniques and open new chances for cultivation of brown algae for production of good manufacturing practice‐compliant bioproducts. 相似文献
5.
Nicholas M. A. Smith Claire Wade Michael H. Allsopp Brock A. Harpur Amro Zayed Stephen A. Rose Jan Engelstdter Nadine C. Chapman Boris Yagound Benjamin P. Oldroyd 《Journal of evolutionary biology》2019,32(2):144-152
Inbreeding (the mating between closely related individuals) often has detrimental effects that are associated with loss of heterozygosity at overdominant loci, and the expression of deleterious recessive alleles. However, determining which loci are detrimental when homozygous, and the extent of their phenotypic effects, remains poorly understood. Here, we utilize a unique inbred population of clonal (thelytokous) honey bees, Apis mellifera capensis, to determine which loci reduce individual fitness when homozygous. This asexual population arose from a single worker ancestor approximately 20 years ago and has persisted for at least 100 generations. Thelytokous parthenogenesis results in a 1/3 of loss of heterozygosity with each generation. Yet, this population retains heterozygosity throughout its genome due to selection against homozygotes. Deep sequencing of one bee from each of the three known sub‐lineages of the population revealed that 3,766 of 10,884 genes (34%) have retained heterozygosity across all sub‐lineages, suggesting that these genes have heterozygote advantage. The maintenance of heterozygosity in the same genes and genomic regions in all three sub‐lineages suggests that nearly every chromosome carries genes that show sufficient heterozygote advantage to be selectively detrimental when homozygous. 相似文献
6.
Understanding the factors that influence the success of ecologically and economically damaging biological invasions is of prime importance. Recent studies have shown that invasive populations typically exhibit minimal, if any, reductions in genetic diversity, suggesting that large founding populations and/or multiple introductions are required for the success of biological invasions, consistent with predictions of the propagule pressure hypothesis. Through population genetic analysis of neutral microsatellite markers and a gene experiencing balancing selection, we demonstrate that the solitary bee Lasioglossum leucozonium experienced a single and severe bottleneck during its introduction from Europe. Paradoxically, the success of L. leucozonium in its introduced range occurred despite the severe genetic load caused by single-locus complementary sex-determination that still turns 30% of female-destined eggs into sterile diploid males, thereby substantially limiting the growth potential of the introduced population. Using stochastic modeling, we show that L. leucozonium invaded North America through the introduction of a very small number of propagules, most likely a singly-mated female. Our results suggest that chance events and ecological traits of invaders are more important than propagule pressure in determining invasion success, and that the vigilance required to prevent invasions may be considerably greater than has been previously considered. 相似文献
7.
Inhibition of methane production from whey by heavy metals – protective effect of sulfide 总被引:1,自引:0,他引:1
A whey solution was used as a substrate for methane production in an anaerobic fixed-bed reactor. At a hydraulic retention
time of 10 days, equivalent to a space loading of 3.3 kg (m3 day)−1, 90% of the chemical oxygen demand was converted to biogas. Only a little propionate remained in the effluent. Toxicity tests
with either copper chloride, zinc chloride or nickel chloride were performed on effluent from the reactor. Fifty per cent
inhibition of methanogenesis was observed in the presence of ≥10 mg CuCl2 l−1≥40 mg ZnCl2 l−1 and ≥60 mg NiCl2 l−1, respectively. After exposure to Cu2+, Zn2+ or Ni2+ ions for 12 days, complete recovery of methanogenesis by equimolar sulfide addition was possible upon prolonged incubation.
Recovery failed, however, for copper chloride concentrations ≥40 mg l−1. If the sulfide was added simultaneously with the three heavy metal salts, methanogenesis was only slightly retarded and
the same amount of methane as in non-inhibited controls was reached either 1 day (40 mg ZnCl2 l−1) or 2 days later (10 mg CuCl2 l−1). Up to 60 mg NiCl2 l−1 had no effect if sulfide was present. Sulfide presumably precipitated the heavy metals as metal sulfides and by this means
prevented heavy metal toxicity.
Received: 8 October 1999 / Received revision: 3 January 2000 / Accepted: 4 January 2000 相似文献
8.
Removal of organic pollutants and of nitrate from wastewater from the dairy industry by denitrification 总被引:3,自引:0,他引:3
The aim of this work was to remove nitrate-N and organic pollutants from wastewater of the dairy industry by denitrification.
An artificially prepared wastewater, containing 250 mg/l nitrate-N and 1.5 g/l whey powder, was completely denitrified with
removal of 90%–93% of the chemical oxygen demand (COD) of the whey powder by suspended or immobilized mixed cultures and by
a suspended or immobilized pure culture that was isolated from the mixed culture inoculum. For the above COD/nitrate-N ratio
of 6:1, the results indicated that the organic compounds of the wastewater served as electron donors for complete denitrification
and that there was no need to add an external carbon source. In batch denitrification assays the suspended or immobilized
mixed cultures proved to be more active and reacted faster than the isolated pure cultures. In continuous denitrification
processes with immobilized pure or mixed cultures, the alginate beads, used for immobilization, were not stable for more than
12 days of incubation. The mixed free cultures removed the nitrate-N and COD continuously with no change of their activity
for at least 15 days at an optimum hydraulic retention time of 0.27 days with a loading rate of 900 mg nitrate-N l−1 day−1.
Received: 13 October 1997 / Received revision: 16 December 1997 / Accepted: 19 December 1997 相似文献
9.
Nadine C. Chapman Brock A. Harpur Julianne Lim Thomas E. Rinderer Michael H. Allsopp Amro Zayed Benjamin P. Oldroyd 《Molecular ecology resources》2015,15(6):1346-1355
The honeybee, Apis mellifera, is the world's most important pollinator and is ubiquitous in most agricultural ecosystems. Four major evolutionary lineages and at least 24 subspecies are recognized. Commercial populations are mainly derived from subspecies originating in Europe (75–95%). The Africanized honeybee is a New World hybrid of A. m. scutellata from Africa and European subspecies, with the African component making up 50–90% of the genome. Africanized honeybees are considered undesirable for bee‐keeping in most countries, due to their extreme defensiveness and poor honey production. The international trade in honeybees is restricted, due in part to bans on the importation of queens (and semen) from countries where Africanized honeybees are extant. Some desirable strains from the United States of America that have been bred for traits such as resistance to the mite Varroa destructor are unfortunately excluded from export to countries such as Australia due to the presence of Africanized honeybees in the USA. This study shows that a panel of 95 single nucleotide polymorphisms, chosen to differentiate between the African, Eastern European and Western European lineages, can detect Africanized honeybees with a high degree of confidence via ancestry assignment. Our panel therefore offers a valuable tool to mitigate the risks of spreading Africanized honeybees across the globe and may enable the resumption of queen and bee semen imports from the Americas. 相似文献
10.
L. Englert A. Biela M. Zayed A. Heine D. Hangauer G. Klebe 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010