Uticaj krioprotektivnog medijuma sa glicerolom na liofilizaciju bakterija mlečne kiseline

The aims of lyophilization (freeze-drying) of lactic acid bacteria are to preserve pure cultures or to prepare starters for the dairy industry. In both cases, the choice of the cryoprotectant is very important. In this work, samples of Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD were freeze-dried in a new cryoprotective medium containing lactose, gelatin and glycerol (medium B). The reference medium contained saccharose, gelatin and skim milk (medium A). Before lyophilization, the eutectic points of both media were determined, because the products must be cooled to a temperature below its freezing point. The success of the cryoprotectants was estimated in terms of the number of surviving organisms after lyophilization. Bifidobacterium breve A71 and Bifidobacterium bifidum BbTD freeze-dried in media A and B showed high survival rates. Bifidobacterium breve A71 showed a greater percentage survival in combination with medium B than with medium A. These results could be utilized in the manufacture of Bifidobacterium breve A71 as a starter in the diary industry because it is a human isolate which, except for acidification, has probiotic activity.Bakterije mlečne kiseline se liofilizuju (suše u zamrznutom stanju) sa ciljem čuvanja kultura na duže vreme ili u formi startera za mlečnu industriju. U oba slučaja važan je izbor krioprotektanata. U ovom radu praćena je liofilizacija Bifidobacterium breve A71 i Bifidobacterium bifidum BbTD u novom krioprotektivnom medijumu sa laktozom, želatinom i glicerolom (medijum B). Referentni medijum sadrži saharozu, želatin i obrano mleko (medijum A). Liofilizaciji prethodi određivanje eutektičke temperature jer se faza zamrzavanja odvija na nešto nižoj temperaturi od eutektičke. Efikasnost krioprotektanata ispitivana je u smislu preživljavanja kultura nakon liofilizacije. Bifidobacterium breve A71 i Bifidobacterium bifidum BbTD liofilizovani u medijumima A i B ostaju u visokom procentu vijabilne. Obe kombinacije krioprotektanata daju relativno visok procenat preživljavanja. Bifidobacterium breve A71 u kombinaciji sa medijumom B ima veći procenat preživljavanja nego u kombinaciji sa medijumom A. Ovi rezultati mogu poslužiti u proizvodnji liofilizovanog Bifidobacterium breve A71 - startera u mlečnoj industriji jer je to humani izolat sa potencijalno dobrim probiotskim osobinama

Mineralized agar-based nanocomposite films: Potential food packaging materials with antimicrobial properties

New mineralized, agar-based nanocomposite films (Zn-carbonate and Zn-phosphate/agar) were produced by a combination of in situ precipitation and a casting method. The presence of minerals significantly influenced the morphology, properties and functionality of the obtained nanocomposites. Reinforcement with the Zn-mineral phase improved the mechanical properties of the carbonate-mineralized films, but had a negligible effect on the phosphate-mineralized samples. Both nanocomposites showed improved optical and thermal properties, better Zn(II) release potential in a slightly acidic environment and exhibited antimicrobial activity against S. aureus. These results suggest that Zn-mineralized agar nanocomposite films could be potentially used as affordable, eco-friendly and active food packaging materials.This is the peer reviewed version of the paper: Malagurski, I., Levic, S., Nesic, A., Mitric, M., Pavlovic, V., & Dimitrijevic-Brankovic, S. (2017). Mineralized agar-based nanocomposite films: Potential food packaging materials with antimicrobial properties. Carbohydrate Polymers, 175, 55–62. [https://doi.org/10.1016/j.carbpol.2017.07.064][https://www.sciencedirect.com/science/article/abs/pii/S0144861717308408?via%3Dihub

Karakterizacija autohtonih sojeva Lactobacillus paracasei na potencijalne probiotičke sposobnosti

Lactic acid bacteria strains isolated from traditional made cheeses constitute a reservoir of unexplored potential in biotechnology. In this study four autochthonous lactobacilli strains, isolated from traditional white brined cheeses and identified as Lactobacillus paracasei (08, 564, 05 and 02), were investigated on potential probiotic ability. The investigation comprised sensitivity to simulated gastrointestinal tract conditions, antimicrobial activity against wide range of pathogens, antibiotic resistance as well as autoaggregation ability. Lactobacillus rhamnosus GG was used as referent strain. Three tested strains grew well in simulated gastrointestinal conditions, but their sensitivity was greater on bile acids and pancreatin compared with pepsin low pH 2.5. The examined strains had different sensitivity to antibiotics, but three strains showed very good antimicrobial activity to pathogens. All strains demonstrated very good autoaggregation ability. For three of four examined strains of Lb. paracasei probiotic potential was similar with referent strain Lb. rhamnosus GG, determined in vitro.Bakterije mliječne kiseline izolirane iz tradicionalnih sireva predstavljaju neiscrpan potencijal u biotehnologiji. U ovom radu 4 soja laktobacila, izolirana iz autohtonih bijelih sireva u salamuri i identificirana kao Lactobacillus paracasei (08, 564, 05 and 02), ispitivana su na potencijalne probiotičke sposobnosti. Ispitivanje je obuhvatilo osjetljivost na simulirane gastrointestinalne uvjete, antimikrobnu aktivnost u odnosu na patogene, antibiotsku rezistentnost i sposobnost autoagregacije. Lactobacillus rhamnosus GG upotrijebljen je kao referentni soj. Tri testirana soja dobro su rasla u simuliranim gastrointestinalnim uvjetima, ali je njihova osjetljivost bila veća u prisustvu žučne kiseline i pankreatina u usporedbi s pepsinom niskog pH 2,5. Ispitivani sojevi pokazali su različitu osjetljivost na antibiotike, a 3 soja su pokazala dobru antimikrobnu aktivnost u odnosu na patogene. Svi su sojevi pokazali visoku sposobnost autoagregacije. Od 4 ispitana soja Lb. paracsei, tri su pokazala dobar probiotički potencijal u usporedbi s referentnim sojem Lb. rhamnosus GG, in vitro uvjetima

CHARACTERIZATION OF THE GOLD MERCAPTOTRIAZOLE COMPLEX USING THE TANDEM QUADRUPOLE MASS SPECTROMETRY (TQD)

This work is aimed to characterize the gold complexes using the electron spray ionization (ESI), and atmospheric solids analysis probe (ASAP), tandem quadrupole mass spectrometer (TQD). It is demonstrated here that the use of the ASAP is more suitable than the ESI for a rapid analysis of the gold coatings in the solid and liquid state. The mass spectra indicate that mercaptotriazole and glycine can coordinate with the gold ion and to build complexes such as [Au-2MT-Gly] and [Au-2MT-2Gly]

Negative-Mode LDI-MS of corrosion products on the surface of AgCu-X (X- Zn, Pd, In) alloys

Copper-silver alloys have widely applied in many different areas such as information and communication technology, rail transportation, power transmission lines, microelectronics, machinery manufacturing, chemical processing industries, coinage, ornamental parts, etc [1, 2]. A group of ternary Ag-Cu alloys with different elements is used for binding different materials (brazing, fillers, and pastes). For example, Ag-Cu-Pd alloys are used in dentistry, as amalgams improvers or joint fillers for different dental materials [3]. Ternary AgCuIn alloy uses as a bonding metal layer; the use of AgCuIn as the bonding metal, greatly reduces the manufacturing costs of LED chip and helps to improve the life of the LED chip. Copper and its alloys belong to the group of semi-noble metals however they are not highly resistant to corrosion in some of the environments [4, 5]. Corrosion has particularly attracted attention due to the significant impact on the performance and reliability of this industrially important material group in their applications, as well as on the economy. Standard methods for characterization of corrosion films are: X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) [6, 7]. The positive mode laser desorption ionization (LDI) mass spectrometry method can be successfully applied to analyze the composition of the corrosion film. In our previous work, it has been shown that the amount of sample required for the LDI method is much smaller than the sample quantity required for the methods mentioned above [8]. The purpose of this work was to study the possibilities of direct analysis of the corrosion films formed on Ag60Cu26Zn14, Ag58.5Cu31.5Pd10, and Ag63Cu27In10 alloys using the negative mode laser desorption ionization (LDI) mass spectrometry method. The corrosion films of Ag60Cu26Zn14, Ag58.5Cu31.5Pd10, and Ag63Cu27In10 alloys were obtained after anodic potentiostatic polarization treatment (at +0.25 V for 5 min in 3.5% wt. NaCl solution). Preliminary results show that the negative mode LDI mass spectra measured from the corrosion film of these alloys contains same ionsAgCl2 - , AgCuCl3 - , CuCl2 - , Cu2Cl3 - , Cu3Cl4 - . This result suggested that main reactions are the formation of CuCl layer on the surface of the Cu rich metallurgical phase and formation of AgCl film on the surface of Ag rich metallurgical phase. ACKNOWLEDGEMENT: This work is the result of the Projects OI 172019 and TR 34033, funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia.VII International School and Conference on Photonics : PHOTONICA2019 : Abstracts of Tutorial, Keynote, Invited Lectures, Progress Reports and Contributed Papers; August 26-30; Belgrad

Synthesis and antimicrobial properties of Zn-mineralized alginate nanocomposites

New bioactive and antimicrobial biomaterials were produced by alginate-mediated biomineralization with Zn-mineral phase. The synthesis procedure is simple, cost-effective and resulted in. two different Zn-mineralized alginate nanocomposites, Zn-carbonate/Zn-alginate and Zn-phosphate/Zn-alginate. The presence of Zn-mineral phase and its type, have significantly affected nanocomposite morphology, stability, total metallic loading and potential to release Zn(II) in physiological environment. Antimicrobial experiments showed that both types of Zn-mineralized nanocomposites exhibit strong antimicrobial effect against Escherichia coli, Staphylococcus aureus and Candida albicans. These results suggest that alginate biomineralization, where minerals are salts of essential metallic ions like Zn(II), represents a'good strategy for designing multifunctional biomaterials for potential biomedical applications.This is the peer reviewed version of the paper: Malagurski, I., Levic, S., Pantic, M., Matijasevic, D., Mitric, M., Pavlovic, V., & Dimitrijevic-Brankovic, S. (2017). Synthesis and antimicrobial properties of Zn-mineralized alginate nanocomposites. Carbohydrate Polymers, 165, 313–321. [https://doi.org/10.1016/j.carbpol.2017.02.064

Synergy of Nd:YAG Picosecond Pulsed Laser Irradiation and Electrochemical Anodization in the Formation of TiO2 Nanostructures for the Photocatalytic Degradation of Pesticide Carbofuran

This study proposes a simple and controlled method for producing TiO2 with phase junction, oxygen vacancies, and Ti3+ by combining picosecond pulsed laser irradiation and electrochemical anodization. Ti mesh was pretreated by irradiating with a picosecond pulsed laser technique using an Nd:YAG laser (1064 nm) at two fluencies, 15 J/cm2 and 30 J/cm2 . The samples were then subjected to electrochemical anodization to form TiO2 nanotube arrays on the previously laser-treated surface. This study will investigate the possibility of forming TiO2 nanotube arrays on a pre-laser-treated Ti substrate and determine their physicochemical and photocatalytic properties. The samples were characterized by FESEM, XRD, Raman, XPS, and UV-Vis DRS. UV-Vis spectroscopy was used to observe the progress of photocatalytic degradation for all samples, and degradation products were determined using GC-MS. With the synergistic effects of phase junction, oxygen vacancies, and Ti3+, the laser-treated TiO2 with 30 J/cm2 showed a higher photocatalytic degradation rate (85.1%) of the pesticide carbofuran compared to non-laser-treated TiO2 (54.8%), remaining stable during successive degradation cycles, which has promising practical applications

MASS SPECTROMETRY FOR STRUCTURAL CHARACTERIZATION OF NON-CYANIDE GOLD COMPLEX

In this work, the possibilities of a mass spectrometry approach towards the characterizations of the electrolyte for decorative gold plating based on mercaptotriazole were studied. All mass spectra were obtained using laser desorption ionization (LDI) method on a commercial matrix assisted laser desorption ionization – time of flight (MALDI-TOF) mass spectrometer. The LDI MS spectra of chloroauric acid gave evidence of the presence of a variety of monomeric and polymeric complexes. LDI MS spectra of the electrolyte obtained from chloroauric acid, glycine and mercaptotriazole revealed existence of the ion at m/z 472 which indicated that the complex [Au(NH2CH2COOH)(C2H2N3S)2]- has been formed

Generation of Au2Cl2n+1 (n = 1-3) cluster ions by laser desorption/ionization mass spectrometry

Gold chloride clusters were generated from an aqueous solution of gold-hydrochloric acid deposited onto the target plate using laser desorption/ionization (LDI) on a commercial matrix assisted laser desorption/ionization –time of flight (MALDI-TOF) mass spectrometric instrument. In our experimental conditions negative mode of LDI mass spectra provided the most valuable informations. The mass peaks at m/z about 339, 499, 571, 641, were assigned to AuCl4-, Au2Cl3-, Au2Cl5-, Au2Cl7-cluster ions, respectively. The Au2Cl5-and Au2Cl7-clusters are detected for the first time in this work. This research showed that LDI MS, thanks to its easy experimental procedure, a soft ionization technique which may be a useful characterization tool in the chemistry of heterogeneous gold clusters.Physical chemistry 2016 : 13th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-30 September 2016

Determination of corrosion products of Ag-Cu alloy by laser desorption ionization mass spectrometry

Silver alloys are generally used in the different fields of industry, including chemical processing, construction, heat exchangers, etc. Although Ag-Cu-Zn-Cd type of alloys, were widely exploited in the second half of the 20th century for their excellent properties, its use is forbidden in the EU due to the high toxicity of cadmium vapors. Ag-Cu-In type of alloy is a good alternative to Ag-Cu-Zn-Cd alloys, with great properties and can be used in various fields of industry. Most common methods for characterization of surface corrosion films of Ag-Cu alloys are: X-ray diffraction (XRD), scanning electron microscopy with energy dispersion spectroscopy (SEM-EDS), Raman spectroscopy and atomic force microscopy (AFM). Our current study focuses on the application of laser desorption ionization mass spectrometry (LDI MS) for determination of corrosion products of Ag-Cu alloy. The aim of this study was to confirm LDI MS as a fast, accurate and reliable method for determination of corrosion products on the surface of Ag-Cu-In alloy.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad