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Tudorache M.,University of Bucharest | Gheorghe A.,University of Bucharest | Negoi A.,University of Bucharest | Enache M.,Institute of Biology Bucharest of the Romanian Academy | And 2 more authors.
Carbohydrate Polymers

Bifunctional catalysts designed as carbohydrate biopolymers entrapping lipase have been investigated for the biotransformation of a natural compound (α-pinene) to oxy-derivatives. Lipases assisted the epoxidation of α-pinene using H2O2 as oxidation reagent and ethyl acetate as both acetate-supplier and solvent affording α-pinene oxide as the main product. Further, the biopolymer promoted the isomerization of α-pinene oxide to campholenic aldehyde and trans-carenol. In this case, the biopolymers played double roles of the support and also active part of the bifunctional catalyst. Screening of enzymes and their entrapping in a biopolymeric matrix (e.g. Ca-alginate and κ-carrageenan) indicated the lipase extracted from Aspergillus niger as the most efficient. In addition, the presence of biopolymers enhanced the catalytic activity of the immobilized lipase (i.e. 13.39 × 103, 19.76 × 103and 26.46 × 103 for the free lipase, lipase-carrageenan and lipase-alginate, respectively). The catalysts stability and reusability were confirmed in eight consecutively reaction runs. © 2016 Elsevier Ltd Source

Baricz A.,Babes - Bolyai University | Baricz A.,Romanian National Institute for Research and Development for Biological Sciences | Cristea A.,Babes - Bolyai University | Muntean V.,Babes - Bolyai University | And 6 more authors.

Perennially stratified salt lakes situated in the Transylvanian Basin (Central Romania) were surveyed for the diversity of culturable halophilic archaea (Fam. Halobacteriaceae). The physical and chemical characteristics of the waters indicated that all the investigated lakes were meromictic and neutral hypersaline. Samples collected from upper, intermediate, and deeper water layers and sediments were used for the isolation of halophilic strains followed by 16S rRNA gene-based identification and phenotypic characterization. The phylogenetic analysis of the 16S rRNA gene sequences revealed that all 191 isolates reported in this study and 43 strains previously isolated were affiliated with the family Halobacteriaceae and classified to 18 genera. Haloferax was the most frequently isolated genus (~47 %), followed by Halobacterium spp. (~12 %), and Halorubrum spp. (~11 %). Highest culturable diversity was detected in Brâncoveanu Lake, the oldest and saltiest of all studied lakes, while the opposite was observed in the most stable and least human-impacted Fără Fund Lake. One strain from Ursu Lake might possibly constitute a novel Halorubrum species as shown by phylogenetic analysis. Several haloarchaeal taxa recently described in Asian (i.e., Iran, China) saline systems were also identified as inhabiting the Transylvanian salt lakes thus expanding our knowledege on the geographic distribution of Halobacteriaceae. © 2015, Springer Japan. Source

Grosu-Tudor S.-S.,Institute of Biology Bucharest of the Romanian Academy | Zamfir M.,Institute of Biology Bucharest of the Romanian Academy | Van der Meulen R.,Vrije Universiteit Brussel | De Vuyst L.,Vrije Universiteit Brussel
European Food Research and Technology

Traditionally fermented foods can be a rich source of diverse lactic acid bacteria (LAB) with interesting functional properties, such as exopolysaccharide (EPS) production. The objectives of this study were to map the mucoid and/or ropy LAB isolated from raw milk and traditionally fermented dairy products, collected in different regions of Romania, to study the species diversity within the samples and to further explore the EPS-producing capacity of the isolates. Seventy-three LAB strains were isolated and identified through (GTG)5-PCR genomic fingerprinting and SDS-PAGE of whole-cell proteins. Lactococcus lactis was the most frequently encountered species, followed by Lactobacillus plantarum, Leuconostoc spp., and Enterococcus spp. Nine strains produced homopolysaccharides (HoPS, glucose monomers), namely L. lactis 1.8; Leuc. citreum 1.10, 1.11, 1.12, 2.8, and 4.11; Leuc. mesenteroides 21.2; Leuc. pseudomesenteroides 20.6; and Weisella confusa/cibaria 38.2, six of them in the concentrations above 10 g/L, both in milk and MRS medium supplemented with sucrose. In all EPS, the glucose constituents were connected by different α-linkages, among which α-1,6-linkages were the most prevalent. © 2013 Springer-Verlag Berlin Heidelberg. Source

Grosu-Tudor S.S.,Institute of Biology Bucharest of the Romanian Academy | Zamfir M.,Institute of Biology Bucharest of the Romanian Academy
Food Biotechnology

A total of 139 lactic acid bacterium (LAB) strains isolated from Romanian traditionally fermented vegetables were screened for the ability to produce exopolysaccharides and for their antagonistic activity against a set of nine LAB strains, three Bacillus strains, and four Gram-negative bacteria. Eighty-five of the tested strains showed a variable antimicrobial activity against Listeria monocytogenes ATCC 1911, 35 of the strains showed a limited inhibition zone against Escherichia coli ATCC25922, and 26 strains against Salmonella enterica ATCC 14024, while 19 strains showed inhibition against one or all three Bacillus strains used as indicators. None of the tested strains showed an antimicrobial activity against Staphylococcus aureus ATCC 25923. Several strains showed antibacterial activity against more than one indicator strain. For instance, Lactobacillus plantarum 307, Lactobacillus brevis 308, and Lactobacillus plantarum/pentosus 358 were active against five of the indicator strains used, while other 23 LAB were active against three indicator strains. In the case of two strains, namely Leuconostoc citreum 344 and Lactobacillus brevis 183, the activity was maintained after neutralizing the pH of the cell-free supernatant likely due to the production of bacteriocins. The gel permeation chromatography-based screening revealed seven EPS-producing LAB strains. Two of the positive strains, namely Leuconostoc citreum 177 and Leuconostoc citreum 52, have been shown to produce large amounts of EPS, of about 20 g/L. All isolated EPS have a high molecular mass, of above 1400 KDa, and a monomer composition dominated by the presence of glucose. © 2013 Taylor and Francis Group, LLC. Source

Zamfir M.,Institute of Biology Bucharest of the Romanian Academy | Grosu-Tudor S.-S.,Institute of Biology Bucharest of the Romanian Academy
World Journal of Microbiology and Biotechnology

Understanding the mechanisms of stress response and adaptation to stress in the case of lactic acid bacteria (LAB), especially in the case of strains with functional properties, is very important when such strains are potential candidates for starter cultures or probiotics. In this context, our study shows the response of some LAB [four exopolysaccharide (EPS)-producing strains and one strain with potential probiotic effect] to the stresses induced by low and high incubation temperatures, acidity, NaCl, and bile salts, often encountered during the technological processes in food or during the passage through the human gastro-intestinal tract. The strains were able to grow at temperatures up to 40 °C (the mesophilic strains) and 47 °C (the thermophilic strain), in medium with an initial pH of at least 4.0 (Lactobacillus acidophilus IBB801), or in the presence of NaCl up to 10 % (Weissella confusa/cibaria 38.2), or bile salts up to 0.2 % (L. acidophilus IBB801). The protein and isoenzyme patterns of the strains subjected to various stress conditions presented several differences compared with the control patterns, among which the overexpression of some proteins of about 50-60 kDa, differences in the bands intensity in the case of the intracellular enzymes, or the complete loss of some of these bands. The best survival to low pH values and high temperatures was observed for strain L. acidophilus IBB801, the candidate probiotic strain. The EPS production of the four tested strains was, in general, directly related to the growth, the highest yields being obtained when strains were incubated at 24 °C. © 2013 Springer Science+Business Media Dordrecht. Source

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