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.

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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.

BACKGROUND: The aim of this study was to evaluate the viscosifying power and mean molecular weight (MMW) of alginate synthesized by Azotobacter vinelandii in a region of very low power input; as well as to scale-up the process of alginate production in a 3 L fermenter using the power input profile (determined in shake flasks) as criterion.

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BACKGROUND Polyhydroxybutyrate (PHB) is a biopolymer with thermo‐mechanical properties like those of plastics produced by the petrochemical industry. These properties are improved in PHBs of high or ultra‐high weight average molecular weight. Azotobacter vinelandii OPNA is a potential producer of large quantities of PHB, having ultra‐high molecular weight by fed‐batch production strategies. RESULTS In batch and fed‐batch cultures at different carbon–nitrogen molar ratios (10, 14 and 18), the OPNA strain produced PHB of high and ultra‐high weight average molecular weight, with values between 2.3 and 6.6 MDa. In this strain, the weight average molecular weight was highly dependent on the initial carbon–nitrogen ratio, reaching the highest value (6.6 MDa) in batch cultures conducted with a carbon–nitrogen ratio of 18 and the lowest (2.3) with a carbon–nitrogen ratio of 10. On the other hand, using a two feeding‐pulses fed‐batch strategy, the highest global PHB volumetric productivity (0.56 g L−1 h−1) and polymer concentration (27.6 g L−1) were obtained. CONCLUSION The OPNA strain accumulated up to 80% of PHB of ultra‐high molecular weight as a function of the initial carbon–nitrogen molar ratio. Using a simple fed‐batch strategy of two feeding‐pulses was possible to produce up to 27 g L−1 of PHB. © 2016 Society of Chemical Industry

Production of γ-decalactone, a compound having peach-like aroma characteristics, by a strain of Trichoderma harzianum is reported here for the first time. Cultures were carried out in a 14 L fermentor using castor oil as the sole carbon source. The filamentous-like growth of the microorganism resulted in highly viscous and nonNewtonian broths, which caused the formation of stagnant zones in the fermentor. T. harzianum was able to produce 260 mg/L of γ-decalactone after 7 days of culture in a stirred fermenter operated at 3.3 s -1 and 1 vvm of air flow rate. The production of γ-decalactone was mainly non-growth associated. The use of high agitation ratessto improve mixingsresulted in celullar lysis. Cell damage occurred at volumetric power drawn as low as 0.2 W/L. Mycelial morphology (mainly hyphal thickness) changed drastically along the culture and was an important influence on the rheology of the broths. All these characteristics make this system an interesting model of study of hydrodynamically complex fermentations involving up to four phases.