Search results for "Actic acid"
showing 10 items of 660 documents
Dynamic optimization of a continuous Lactide ring-opening polymerization process
2019
An increasing attention has been paid to the production of the polylactic acid (PLA) in recent years, owing to its properties as a biodegradable thermoplastic besides the fact that it is derived from renewable resources. PLA is industrially produced by ring opening polymerization of lactide. This reaction is sensitive to deviations in the operating conditions that highly affect the reaction rate and the polymer properties. Therefore, a process monitoring and control policy is crucial in order to restore the nominal conditions in case of drift. In this paper, a continuous PLA process is considered with three cascade reactors, two tubular and one loop reactor, that is described by partial dif…
Polymeric scaffolds based on blends of poly-l-lactic acid (PLLA) with poly-d-l- lactic acid (PLA) prepared via thermally induced phase separation (TI…
2012
Porous scaffolds based on blends of high crystalline Poly-L-lactic acid (PLLA) with low crystalline poly-D-L-lactic acid (PLA) were prepared via Ther- mally Induced Phase Separation (TIPS), with the aim of exploring the possibility to control the degradation behaviour of the PLA-based scaffold, simultaneously pre- serving the morphological characteristics required for tissue engineering applica- tions. Porous foams with different PLLA/PLA weight ratios (from 95/5 to 60/40) were produced and characterised in terms of pore size, porosity, and thermal properties. The scaffolds present an open porosity, with average pore sizes ranging from 30 to 70 lm. Results showed that, when dealing with a P…
A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production
2014
Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at th…
Effect of small amounts of poly(lactic acid) on the recycling of poly(ethylene terephthalate) bottles
2011
Abstract Poly(ethylene terephthalate) (PET) is one of the most used commodity polymers, especially for food and beverage applications, and its recycling is of great importance because of the possible use in the textile and construction industries. On the other hand, the interest in biodegradable polymers has led, in recent years, to the use of materials such as poly(lactic acid) (PLA) also in the food and beverage industry. The presence of small amounts of PLA in the PET waste can significantly affect the post-consumer recycling process. In this work, the effect of the presence of small amounts of PLA on the recycling of PET bottles is investigated by rheological, mechanical, morphological …
Lactobacillus vini sp. nov., a wine lactic acid bacterium homofermentative for pentoses.
2006
Six strains with more than 99·5 % 16S rRNA gene sequence similarity, identical internal spacer region profiles and restriction analysis of the amplified 16S rRNA gene patterns were isolated from fermenting grape musts during independent studies carried out in France and Spain many years apart. Strains are Gram-positive, motile, facultatively anaerobic rods that do not exhibit catalase activity and have the ability to utilize pentose sugars (ribose and/or l-arabinose), although they are homofermentative bacteria. Strains ferment pentoses exclusively yielding lactic acid as the end product. A broad set of molecular techniques has been applied to characterize these strains and the results show…
Study on the reduction of acrylamide in mixed rye bread by fermentation with bacteriocin-like inhibitory substances producing lactic acid bacteria in…
2013
Abstract This study mainly focuses on a strategy for reducing of acrylamide in cereal products, predominantly in bakery products. The effect of mesophilic lactic acid bacteria (LAB) strains as well as a novel fermentation media on the bases of extruded rye wholemeal on the acrylamide formation in mixed rye bread of different weight of loaf was studied. The LC–MS/MS method for acrylamide determination in bread crumb has been applied. Addition of 15% low pH (pH 3.4–4.3) fermented product to bread dough, which were produced by using commercial strain Lactobacillus casei and bacteriocin-like inhibitory substances (BLIS) producing strains Lactobacillus sakei KTU05-6 , Pediococcus acidilactici KT…
Molecular characterization of the phenolic acid metabolism in the lactic acid bacteria Lactobacillus plantarum
2001
The lactic acid bacteria Lactobacillus plantarumdisplays substrate-inducible decar- boxylase activities on p-coumaric, caffeic and ferulic acids. Purification of the p-coumaric acid decarboxylase (PDC) was performed. Sequence of the N-terminal part of the PDC led to the cloning of the corresponding pdc gene. Expression of this gene in Escherichia colirevealed that PDC displayed a weak activity on ferulic acid, detectable in vitro in the presence of ammonium sulfate. Transcrip- tional studies of this gene in L. plantarum demonstrated that the pdc transcription is phenolic acid- dependent. A mutant deficient in the PDC activity, designated LPD1, was constructed to study phe- nolic acid altern…
Advanced descriptors for long-range noncovalent interactions between SARS-CoV-2 spikes and polymer surfaces.
2021
The recent pandemic triggered numerous societal efforts aimed to control and limit the spread of SARS-CoV-2. One of these aspects is related on how the virion interacts with inanimate surfaces, which might be the source of secondary infection. Although recent works address the adsorption of the spike protein on surfaces, there is no information concerning the long-range interactions between spike and surfaces, experimented by the virion when is dispersed in the droplet before its possible adsorption. Some descriptors, namely the interaction potentials per single protein and global potentials, were calculated in this work. These descriptors, evaluated for the closed and open states of the sp…
Glucose, Lactate, and Ketone Body Utilization by Human Mammary Carcinomas in Vivo
1985
Uncontrolled growth, one of the fundamental properties of malignant tumors, requires a great supply of energy. This energy can be derived from the use of a variety of substrates. Besides glucose oxidation and glucose breakdown to lactic acid, the turnover of endogeneous substrates such as amino acids, free fatty acids and ketone bodies is well documented in vitro. However, under in vivo conditions, only glucose utilization has been investigated in detail, using tumor isotransplants in rodents. For human tumors, only scarce data is available, derived mainly from clinical observations rather than from systematic studies.