Display omitted
► Pseudomonas chlororaphis was investigated for production of mcl-PHA latex under controlled conditions on bioreactor scale ► A surplus material, namely saturated biodiesel fraction ...from animal waste lipids, was used as the sole carbon source ► A detailed kinetic analysis of the bioprocess is provided ► Productivity of the mcl-PHA latex is competitive to other mcl-PHA producing organisms on expensive carbon sources.
A novel description of mcl-PHA biosynthesis by Ps. chlororaphis from tallow-based biodiesel as an inexpensive carbon feed stock is presented. Fermentation protocols, kinetic analysis, an efficient product recovery strategy, and product characterization are included. Maximum specific growth rates (μmax.) of 0.08 h−1, 0.10 h−1 and 0.13 h−1, respectively, were achieved in three different fermentation set-ups. Volumetric productivity for mcl-PHA amounted to 0.071g/L h, 0.094g/L h and 0.138g/L h, final intracellular PHA contents calculated from the sum of active biomass and PHA from 22.1 to 29.4wt.-%, respectively. GC-FID analysis showed that the obtained biopolyester predominantly consists of 3-hydroxyoctanoate and 3-hydroxydecanoate, and, to a minor extent, 3-hydroxydodecanoate, 3-hydroxynonanoate, 3-hydroxyhexanoate, and 3-hydroxyheptanoate monomers. The overall distribution of the monomers remained similar, regardless to working volumes, biodiesel concentrations and pre-treatment of the inoculum.
► Valuable mathematical models for PHA production by Cupriavidus necator on combined substrates. ► PHA production on waste substrates from biodiesel (FAME and glycerol). ► New low structured model ...for fed-batch fermentation on glucose with glycerol. ► New low structured model for fed-batch fermentation on FAME with valeric acid. ► In silico optimized feeding of C-sources and PHB/PHBV content by mathematical models.
Two low structured mathematical models for fed-batch production of polyhydroxybutyrate and polyhydroxybutyrate-co-hydroxyvalerate by Cupriavidus necator DSM 545 on renewable substrates (glycerol and fatty acid methyl esters-FAME) combined with glucose and valeric acid, were established. The models were used for development/optimization of feeding strategies of carbon and nitrogen sources concerning PHA content and polymer/copolymer composition. Glycerol/glucose fermentation featured a max. specific growth rate of 0.171h−1, a max. specific production rate of 0.038h−1 and a PHB content of 64.5%, whereas the FAME/valeric acid fermentation resulted in a max. specific growth rate of 0.046h−1, a max. specific production rate of 0.07h−1 and 63.6% PHBV content with 4.3% of 3-hydroxyvalerate (3HV) in PHBV. A strong inhibition of glycerol consumption by glucose was confirmed (inhibition constant ki,G=4.28×10−4gL−1). Applied concentration of FAME (10–12gL−1) positively influenced on PHBV synthesis. HV/PHBV ratio depends on applied VA concentration.
An easy and efficient method for the separation of saturated and unsaturated fatty acid mono alkyl esters, prepared from animal fat, was developed. The most efficient separation was achieved by the ...use of solvents such as methanol and acetone at low temperatures. The dilution of the alkyl esters with 10 times the amount of solvent (10:1 v/w) and storage of the mixture for 4 h at −22 °C could be defined as optimum conditions. After filtration of the saturated fraction at the corresponding temperature very pure fractions were obtained. For fatty acid methyl esters deriving from tallow, with an initial content of saturated fatty acids of almost 50 %, a saturated ester fraction with only 5 % unsaturated fatty acids and an unsaturated ester fraction with about 9 % of saturated fatty acids could be obtained. The solvent easily could be recovered by distillation. In addition fatty acid ethyl, 1-propyl, 2-propyl, 1-butyl, tert-butyl and 3-methyl-1-butyl esters were prepared and separated into saturated and unsaturated fractions. All fractions were analyzed according to the fatty acid compositions and showed similar or slightly worse results compared to the methyl esters. The cold filter plugging points of the unsaturated fractions were measured, showing the lowest value for the unsaturated methyl ester fraction at −26 °C. The fractionation with the use of solvents is an easy tool in order to obtain fatty acid alkyl esters with excellent cold temperature behavior out of animal fat.
mcl-PHA biosynthesis by Pseudomonas citronellolis from tallow-based biodiesel as inexpensive carbon feed stock was accomplished. Fermentation protocols, kinetic analysis, an efficient product ...recovery strategy, and a detailed product characterization are presented.
A maximum specific growth rate, μmax. of 0.10 and 0.08h−1, respectively, was achieved in two different fermentation set-ups. Volumetric productivity for mcl-PHA amounted to 0.036g/Lh and 0.050g/Lh, final intracellular PHA contents calculated from the sum of active biomass and PHA to 20.1 and 26.6wt.%, respectively. GC-FID analysis showed that the obtained biopolyester predominantly consists of 3-hydroxyoctanoate and 3-hydroxydecanoate, and, to a minor extent, 3-hydroxydodecanoate, 3-hydroxynonanoate, 3-hydroxyhexanoate, and 3-hydroxyheptanoate monomers. This was confirmed by 1H- and 13C NMR, also evidencing the occurrence of low quantities of unsaturated and 3-hydroxyvalerate building blocks. High purity of the recovered materials was proofed by elemental analysis. Regarding the results from thermogravimetric analysis, differential scanning calorimetry and molecular mass determination, results were in a range typical for this type of PHA (1st fermentation: decomposition temperature Td=296°C, peak of melting range Tm=48.6°C; glass transition temperature Tg=−46.9°C, degree of crystallinity Xc=12.3%, Mw=66,000, Mn=35,000, dispersity index Pi=1.9; 2nd fermentation: Td=295°C, Tm=53.6°C, Tg=-43.5°C, Xc=10.4%, Mw=78,000, Mn=196,000, Pi=2.5).
Abstract
Polyhydroxyalkanoates (PHAs) with tailored properties are needed to meet consumer demands regarding the use of eco-compatible biobased polymeric materials and relevant plastic items. ...Inserting 3-hydroxvalerate (3HV) monomeric units in PHA biopolyesters results in poly(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate (PHBHV) copolyesters aimed at their conversion into production of biodegradable eco-friendly plastic items. As inexpensive novel precursor substrate structurally related to 3HV, a mixture of odd-numbered carboxylic acids with 9-17 carbon atoms was produced by oxidative ozonolysis of alkenes. This mixture was successfully applied for biomediated PHBHV production by Cupriavidus necator. Applying this mixture as carbon substrate, a molar 3HV fraction exceeding 0.12 was obtained. The isolated copolyesters featured a low degree of crystallinity, narrow molar mass distribution, and low melting temperatures. These properties should make application of the novel 3HV-precursors interesting for large-scale production of easily processable copolyesters.
The Middle Ages are generally considered as a time where literary production that can be regarded as scholarly adhered to the ideals of ordo and norm. But is this still true for the 15th century? ...Investigations undertaken in the context of a thesis at the University of Potsdam suggest the contrary: In scholarly descriptions of the Hispania, a number of diff erent strategies of processing information from older works could be identifi ed. Th ey range from simple citation over a careful review of established knowledge all the way to generating new information based on older texts or even applied knowledge.
2008 Visualization Challenge Nesbit, Jeff; Bradford, Monica; De Stefano, Mario ...
Science (American Association for the Advancement of Science),
09/2008, Letnik:
321, Številka:
5897
Journal Article
Effectiveness of seasonal influenza vaccination varies between individuals and might be affected by vaccination history among other factors. Here we show, by monitoring frequencies of CD4 T cells ...specific to the conserved hemagglutinin epitope HA
and titres of IgG against the corresponding recombinant hemagglutinin protein, that antigen-specific CD4 T cell and antibody responses are closely linked to pre-existing immunity and vaccine history. Upon immunization, a strong early reaction is observed in all vaccine naïve participants and also in vaccine experienced individuals who have not received the respective seasonal vaccine in the previous year. This response is characterized by HA
specific CD4 T cells with a follicular helper T cell phenotype and by ascending titers of hemagglutinin-specific antibodies from baseline to day 28 following vaccination. This trend was observed in only a proportion of those participants who received the seasonal vaccine the year preceding the study. Regardless of history, levels of pre-existing antibodies and CD127 expression on CD4 T cells at baseline were the strongest predictors of robust early response. Thus, both pre-existing immunity and vaccine history contribute to the response to seasonal influenza vaccines.
PDF