The spectroscopic characterization of zinc metaphosphate glasses, singly and doubly doped with Ce3+ and Mn2+ ions, is performed through excitation and emission spectra and decay time measurements. The weak yellow emission of Mn2+ is significantly enhanced by means of an efficient energy transfer from Ce3+ to Mn2+ ions. The efficiency of the energy transfer has been estimated based on spectroscopic data, and turned out to be about 53%. From spectroscopic data it can also be inferred that the energy transfer is nonradiative in nature and it takes place between Ce3+ and Mn2+ clusters formed in the glass through a short-range interaction mechanism. This impurity clustering appears to be a relevant finding for the design of efficient conversion phosphors of ultraviolet to visible light.

Extracellular laccases from basidiomycetes are produced only in small amounts. It is therefore important to increase process productivity for potential industrial applications. The results from this study enable the selection Trichoderma strains capable of increasing laccase production by P. ostreatus or A. bisporus in dual cultures.

No abstract

Microbial polymers have diverse chemical structures, which determine their functional properties. Many microbial sources produce either intracellular or extracellular biopolymers. For example, Azotobacter vinelandii is a non-pathogenic soil bacterium that produces alginate, an extracellular polysaccharide. Alginates are used mainly in the food and pharmaceutical industries as stabilizing, thickening, gel-or film-forming agents. Due to its characteristics of biocompatibility, biodegradability and non-antigenicity, new applications for alginate are being discovered, such as biomaterial in the biomedical field and tissue engineering.It is well established that alginate is first synthesized as a polymannuronate from its cytosolic precursor. However, the mechanisms involved in the polymerization, modification (acetylation, epimerization and depolymerization) and translocation of alginate have been poorly elucidated. Two of the most important parameters in alginate production by A. vinelandii are dissolved oxygen tension (DOT) and the oxygen supply conditions, as these impact both the polymer concentration and its composition, particularly its molecular weight (MW). Several studies have revealed that increased alginate molecular weight occurs in oxygen limited conditions, specifically at oxygen concentrations near zero. This article reviews recent studies examining the influence of oxygen, under limitation (microaerophilic) and non-limitation conditions (measured as DOT and oxygen transfer rate, OTR), on the polymerization and degradation of alginate produced by A. vinelandii. This review also provides evidence for understanding these processes at the cellular level and the effect of oxygen on alginate biosynthesis.