Effect of high iron concentrations on iron uptake and growth of a coastal diatom Chaetoceros sociale

The growth and iron uptake of the coastal marine diatom Chaetoceros sociale were experimentally measured in batch experiments at 10°C to which an acidic Fe(III) stock solution was added. The direct input of Fe(III) into the culture media induced the highest iron uptake rate (~3.4 to 4.2 × 10–16 mol Fe cell–1 d–1) by C. sociale during the first day of the incubation, resulting from the supply of bioavailable inorganic Fe(III) species at levels above its expected equilibrium value (~0.1 nmol l–1) with solid amorphous Fe(III) hydroxide in seawater. The iron uptake rate during the first day of incubation in solid amorphous Fe(III) hydroxide medium aged for 1 d at 10°C was approximately 50% lower than that in the direct Fe(III) input media. We used a modified approach in which further iron uptake by C. sociale from external iron in the direct Fe(III) input media was prevented by adding hydroxamate siderophore desferrioxamine B (DFB) during cultivation. After the addition of DFB, the highest growth rate (~0.5 to 0.6 d–1) of C. sociale by intracellularly stored Fe in the direct Fe(III) input media was maintained for a few days since no iron uptake was observed after the DFB addition. The growth rate was independent of the amount of intracellularly stored Fe. However, the maximal cell yields appeared to be relatively dependent on the amount of intracellularly stored Fe, suggesting the presence of a critical concentration of intracellular Fe (minimum cellular Fe for growth) for phytoplankton growth (~1 × 10–16 mol Fe cell–1 for C. sociale). In the present study, maximal and minimal Fe quotas were 3.4 to 4.2 × 10–16 and ~1 × 10–16 mol Fe cell–1 (the maximal/minimal Fe ratio of 3.4 to 4.2), respectively. The high iron uptake and storage capacity in C. sociale allows this species to accumulate excess iron at high concentrations of bioavailable inorganic Fe species and to support up to 1.8 to 2.1 cell divisions without any additional iron uptake. In addition, we attempted to model the effect of luxury uptake on growth, as biodilution of cellular Fe eventually decreases the Fe quota to a critical threshold

Cultivation of Agaricus blazei on Pleurotus spp. spent substrate

The aim of this work was the use of Pleurotus ostreatus and Pleurotus sajor-caju for the previous lignocellulolytic decomposition of banana tree leaf straw and the further use of the degraded straw as substrate for the culture of Agaricus blazei. For optimising the production of A. blazei in terms of yield (Y%) and biological efficiency (BE%), adjustments to the composition of the substrate were evaluated in a 2(5) experimental design. The following components were tested in relation to % of substrate dry mass: urea (1 and 10%), rice bran (10 or 20%) or ammonium sulphate (0 or 10%), inoculum (10 or 20%) and the casing material (subsoil or burned rice husks). The best results (79.71 Y% and 6.73 BE%) were found when the substrate containing 10% of rice bran, without ammonium sulphate, inoculated with 20% and covered with subsoil was used.<br>O cultivo de fungos comestíveis e medicinais utilizando resíduos da agroindústria vem se apresentando como uma alternativa econômica para o pequeno produtor rural, favorecendo a agricultura familiar do nordeste catarinense. Este trabalho avaliou o fungo Pleurotus para a decomposição lignocelulolítica de palha de folhas de bananeira e a utilização da palha residual como substrato para o cultivo de Agaricus blazei. Ajustes na composição do substrato residual de Pleurotus, tais como o tipo e a concentração da fonte de nitrogênio, a porcentagem de inóculo e a camada de cobertura, foram avaliadas. O substrato residual que mais favoreceu a produção de A. blazei em Eficiência Biológica (6,73%), Rendimento (79,71%) e menor tempo para emissão do primeiro primórdio (27 dias) foi o substrato residual de P. ostreatus inoculado com 20% de inóculo (ms), 10% de farelo de arroz (ms), sem sulfato de amônio e utilizando terra de subsolo como camada de cobertura