No abstract

Microbial mats are coastal ecosystems that consist mainly of cyanobacteria, primary producers in these habitats that play an important role in stabilising delta sediments. However, these ecosystems are subject to various kinds of pollution, including metal contamination, placing their survival at risk. Among heavy metals, copper is an essential metal at low doses and toxic at high doses. This metal is present in different pesticides used in rice production, a thriving agro-industry in the Ebro Delta (Spain). For several years, our group has been studying the Ebro Delta microbial mats and has developed a method for determining the effect that metals cause on cyanobacteria populations. This method is based on confocal laser microscopy coupled to a spectrofluorometer, which rapidly provides simultaneous three-dimensional information on photosynthetic microorganisms and their fluorescence spectra profiles. The current study determines the copper effect on different photosynthetic microorganisms from culture collection (Chroococcus sp. PCC 9106 and Spirulina sp. PCC 6313) and isolated from the environment (Microcoleus-like and the microalga DE2009). Comparing all results obtained it can be observed that the minimum dose of Cu that is capable of significantly altering chlorophyll a (chl a) fluorescence intensity were 1 × 10(-7) M in Chroococcus sp. PCC 9106; 1 × 10(-7) M in Spirulina sp. PCC 6313; 3 × 10(-7) M in Microcoleus and 5 × 10(-6) M in the microalga DE2009. Moreover, the sensitivity of the technique used was 1 × 10(-7) M.

Tallow is produced in leather manufacturing, particularly in the fleshing stage. It contains large amounts of fat, which, in most industrial plants, pollutes water and soil due to poor disposal. In order to take advantage of this solid waste, chemical processes have been applied to transform the fats extracted from tallow into biodiesel. In this work, an extraction technique involving non-polar solvents pressurized at 15 psi. With gasoline, a 51,0% fat recovery was obtained. The quality of the extracted fat was determined by analyzing density, viscosity, melting point, moisture, acidity, and acidity, peroxides, saponification, and iodine indices. Biodiesel was obtained via transesterification reactions with methanol and sodium hydroxide. The content of methyl esters produced in the reaction was characterized by means of gas chromatography coupled with mass spectrometry, where the methyl esters of palmitic and oleic fatty acids were identified as major components.