How much nitrogen is fixed by biological symbiosis in tropical dry forests? 1. Trees and shrubs

Despite the recognized importance of the process, estimates of the amount of nitrogen fixed by biological symbiosis in tropical dry forests are almost nonexistent. We estimated the nitrogen fixed annually by the leaves of trees and shrubs at sites regenerating for 16 and 38?years and in an old-growth dry forest using ¹⁵N abundance methodology. The total leaf biomass (1,824?C3,036?kg?ha^?1) and nitrogen contents (62?C90?kg?ha^?1) did not differ among the areas. In all of the areas, most of the leaf biomass belonged to legume plants, but the proportion of the N₂-fixing legumes decreased with increasing regeneration time. In the 16-year regenerating area, almost all of the N was in the leaves of the N-fixing Mimosa tenuiflora plants, but fixation was absent or very low as it was in the N-fixing species present in the 38-year regenerating area. In the old-growth Caatinga, all of the N-fixing species (M. tenuiflora, Piptadenia stipulacea and Anadenanthera colubrina) had large proportions (47?C62?%) of their N derived from atmospheric N₂, but the amount of fixed N (6?kg?ha^?1) was a small proportion of the total leaf N because these plant species were a small part of the vegetation. The total input of biologically fixed N to the old-growth forest was similar in magnitude to an estimate made for a humid tropical forest in Amazonia.     

How much nitrogen is fixed by biological symbiosis in tropical dry forests? 2. Herbs

Although biological nitrogen fixation (BNF) is considered the main input of N in mature and regenerating native tropical vegetation, it has seldom been quantified. Biomass and N accumulation and fixation were determined for spontaneously occurring herbaceous species in caatinga areas in four regeneration stages (2, 17, 39 and >50?years after abandonment from agricultural use). BNF was estimated using the ¹⁵N natural-abundance method. The 2-year regeneration area had the highest total herb (6,355?kg?ha^?1) and legume (262?kg?ha^?1) biomass production, N stocks (82?kg?ha^?1) and fixed N (5.0?kg?ha^?1). N₂-fixing legumes (nine species in the sampled area) contributed over 97?% of legume biomass in all areas. Macroptilium gracile added the largest amount of N (3.9?kg?ha^?1 in the 2-year regeneration area) because of its large biomass production (205?kg?ha^?1), although it was not the species with the highest proportion of fixed N (76?%). All of the N₂-fixing species obtained large proportions of their N from symbiosis, most of them more than 50?%.However, the amounts of fixed N per unit area were relatively low (0.22?C5.00?kg?ha^?1) because the biomass of N₂-fixing species was always less than 5?% of the total herb biomass.     

Coal beneficiation of Candiota mine by dry jigging

The objective of this work is to test dry jigging, operated with air, to eliminate pyrite nodules and liberated clays from Candiota coal. Candiota mine is the biggest Brazilian Coal deposit, which is beneficiated for fueling a thermoelectric plant. This coal presents a high degree of liberated pyrite in a wide range of densities. Hence, gravity separation of pyrite appears apparently obvious. However, any wet treatment results difficult due to the high porosity of the material as a consequence of its low rank. For that reason, dry jigging was proved instead with encouraging results. Samples from the upper layer of the seam, which had around 1.8% sulfur and about 51% ash, appeared after jigging with about 0.7% sulfur and near 47% ash. After these results, pilot jigs are planned to install at the plant.     

Production and characterization of recombinant cyprosin B in Saccharomyces cerevisiae (W303-1A) strain

The Saccharomyces cerevisiae W303-1A strain transformed with a centromeric plasmid containing CYPRO11, which codifies the aspartic protease cyprosin B, was grown in a 3 l bioreactor under aerobic conditions. Expression of cyprosin B is directly dependent on the concentration of galactose used as the inducer and carbon source in 1% yeast extract, 2% bactopeptone, and 4% galactose in culture medium. For 4% of galactose, 209 mg.l(-1) total protein, and 1036 U.ml(-1) recombinant cyprosin B activity were obtained from 6.1 g dcw.l(-1) biomass. The recombinant cyprosin B, purified by two consecutive anion-exchange chromatographies (diethyl amino-ethyl [DEAE]-Sepharose and Q-Sepharose XK-16 columns), shows a specific activity of 62 x 10(3) U.mg(-1), corresponding to a purification degree of 12.5-fold and a recovery yield of 25.6% relative to that in fermentation broth. The proteolytic activity of recombinant cyprosin B is optimal at 42 degrees C and pH 4.5. The recombinant cyprosin B activity is 95% inhibited by pepstatin A, which confirms its aspartic protease nature. The pure recombinant cyprosin B is composed of two subunits, one with 14 and the other with 32 kDa. It exhibits clotting activity, similar to that of the natural enzyme from Cynara cardunculus flowers. The results reported here show that recombinant cyprosin B, the first clotting protease of plant origin produced in a bioreactor, can now be produced in large scale and may constitute a new and efficient alternative to enzymes of animal or fungal origin that are widely used in cheese making.     

A study of the drainages of the pyrite mines of Aljustrel (Portugal)

Characterization of the pollution charge of drainages from pyrite mines of Aljustrel (Portugal) was made. Laboratory experiments were performed in order to recover copper by cementation and remove iron, zinc and acidity by neutralization with lime. It was found that the removal of the metal ions is completed when pH reaches a step at 5.0–5.5, whichever the ratio between Fe(II) and Fe(III).     

Molecular differentiation of the species of two squid families (Loliginidae and Ommastrephidae) based on a PCR study of the 5S rDNA gene

The present study aimed to demonstrate the effectiveness of the 5s rDNA gene for the identification of commercially-valuable species of cephalopod belonging to the families Loliginidae and Ommastrephidae. Our results demonstrate distinct banding patterns in each of the six species sampled (Loligo surinamensis; Loligo sanpaulensis; Lolliguncula brevis; Sepiotheuthis sepioidea; Ornithoteuthis antillarum; Illex argentinus), as well as diagnostic traits at the genus and probably family levels. The results emphasize the efficiency of the 5s rDNA marker as a low-cost and rapid forensic technique, which not only permits the identification of species, but also differentiation of members of the Loliginidae and Ommastrephidae.     

Enzymatic synthesis of sugar esters and their potential as surface-active stabilizers of coconut milk emulsions

Sugar esters are compounds with surfactant properties (biosurfactants), i.e., capable of reducing the surface tension and promote the emulsification of immiscible liquids. On the other hand, as with all emulsions, coconut milk is not physically stable and is prone to phase separation. Therefore, the aim of this work was to evaluate the synthesis of fructose, sucrose and lactose esters from the corresponding sugars using Candida antarctica type B lipase immobilized in two different supports, namely acrylic resin and chitosan, and evaluate its application in the stabilization of coconut milk emulsions. The enzyme immobilized on chitosan showed the highest yield of lactose ester production (84.1%). Additionally, the production of fructose ester was found to be higher for the enzyme immobilized on the acrylic resin support (74.3%) as compared with the one immobilized on chitosan (70.1%). The same trend was observed for the sucrose ester, although with lower percentage yields. Sugar esters were then added to samples of fresh coconut milk and characterized according to their surface tension, emulsification index and particle size distribution. Although the microscopic analysis showed similar results for all sugar esters, results indicated lactose ester as the best biosurfactant, with a surface tension of 38.0 N/m and an emulsification index of 54.1%, when used in a ratio of 1:10 (biosurfactant:coconut milk, v/v) for 48 h experiments.     

Volatile fraction of DOP “Castelo Branco” cheese: Influence of breed

“Castelo Branco” cheese is a Portuguese DOP cheese made from raw ewe’s milk coagulated with Cynara cardunculus, ripened for at least 40 days. “Merino da Beira Baixa” pure race is frequently used to produce milk for this cheese, however, exotic races such as Assaf and crusade of these two races are also used. The aim of this work has been to compare the volatile profile and sensory characteristics of DOP “Castelo Branco” cheeses manufactured during winter season with milk of breeds from Merino, Assaf and crusade of these two races and identify volatile compounds that can distinguish these cheeses.     

A Refinement Strategy for Circus

We present a refinement strategy for Circus, which is the combination of Z, CSP, and the refinement calculus in the setting of Hoare and Hes unifying theories of programming. The strategy unifies the theories of refinement for processes and their constituent actions, and provides a coherent technique for the stepwise refinement of concurrent and distributed programs involving rich data structures. This kind of development is carried out using Circuss refinement calculus, and we describe some of its laws for the simultaneous refinement of state and control behaviour, including the splitting of a process into parallel subcomponents. We illustrate the strategy and the laws using a case study that shows the complete development of a small distributed program.