Effect of herbicides on photosynthetic electron transport and on the growth of the alga Scenedesmus quadricauda

The inhibitory effect of herbicides on the Hill reaction (with 2,6-dichloro-phenol-indophenol as acceptor) and their influence on development of the alga <i>Scenedesmus quadricauda</i> was studied. The following herbicides were tested: 2,4-D, Gramoxone, Afalon, Kresamone, CIPC and Simazine. The results are discussed in terms of the mechanism of action of the investigated herbicides.

Cultivo en efluentes urbanos del alga Scenedesmus quadricauda (Sphaeropleales: Scenedesmaceae) y su potencial para biodiesel: perfil de ésteres metílicos de ácidos grasos

Microalgae stand as biodiesel feedstock for high productivity and good quality of lipids. This paper presents the fatty acid methyl ester profile of Scenedesmus quadricauda. The culture was grown in Trelew city sewage, Patagonia, Argentina, in 20L at 23±1ºC, 12:12 photoperiod, fluorescent lighting tubes at 33μE m-2s-1 and agitation by air bubbling. Percentage of fatty acid methyl esters was 7,89%, it was determined by Lepage method. The profile was obtained by gas chromatography. Methyl linolenate (C18: 3) and polyunsaturated (≥4 double bonds) ester fractions were 15,06% and 0,83% respectively. The unsaturation index (0,84) was estimated and some biodiesel parameters were calculated through it: kinematic viscosity (4,68mm s -2), iodine value (75,15), cetane number (57,28), cloud point (8,78°C), specific gravity (0,88) and higher heating value (40,01MJ/kg). Linolenic acid ester fraction is above the limit value of EN 14214:2003 (<12%). However, one can modify unsaturation in this strain by varying the temperature. It is also possible to increase the lipid proportion by maintaining the culture at low nitrogen concentration by venting NH3 to increase pH during photosynthesis.

The use of selenium-enriched alga Scenedesmus quadricauda in a chicken diet

The selenium-enriched Scenedesmus biomass of patented selenium-resistant strain SeIV was tested in a broiler chicken diet in comparison with sodium selenite supplementation. Feed conversion, mortality and live weight were not significantly influenced by the source of selenium. Supplementation of either form of selenium significantly increased the Se concentration in breast muscle with a more pronounced effect (P &lt; 0.001) caused by selenium enriched Scenedesmus (635 &mu;g/kg DM, 229 &mu;g/kg DM in control). Breast meat of chickens fed a diet with sodium selenite or Se-Scenedesmus had a significantly (P &lt; 0.001) higher value of glutathione peroxidase activity (0.329 &mu;mol/g, 0.361 &mu;mol/g) compared to the basal diet (0.190 &mu;mol/g). The inclusion of Se-Scenedesmus biomass in the diet enhanced (P = 0.021) oxidative stability of meat expressed as reduced malondialdehyde in breast meat after 10-day cooler storage. Se-enriched Scenedesmus can be a good source of organic selenium for the production of Se-enriched chicken meat for further use in human diets. Furthermore, the Se-resistant strain SeIV was found advantageous for its fast and easy production of Se-enriched biomass.