Growth Kinetics, Light Dynamics, and Lipid Production in Microalgae from Sugar-Mill Ponds

Sugar-mill wastewaters have potential to support microalgal biomass production for use as a biofuel feedstock (lipid source). Growth kinetics, light dynamics, and lipid production in multispecies-microalgae cultures collected from a sugar-mill pond are reported in this paper. Lipid content of the microalgae collected from the pond water was 14.5 % (w/w). Culturing the same microalgae in a photobioreactor on the pond wastewater supplemented with Gillard’s F/2 and CO2, and irradiated with 151 to 337 μmol s–1 m–2 artificial light produced cells with lipid contents of 11 % (w/w) at 25 °C, 35 % (w/w) at 31 °C, and 28.6 % (w/w) at 33 °C. The maximum specific growth rates (μmax) at 25 °C, 31 °C, and 33 °C were 0.64 d–1, 2.5 d–1, and 2.7 d–1, respectively. Under these conditions, cell densities as high as 1020 g cell dry mass (CDM) m–3 were recorded. Total scalar irradiance attenuation coefficient (k0) was 0.275 m–1 in clear water and 30.5 m–1 in the dense culture. The attenuation coefficient of irradiance due to biomass (kB) was found to be a linear function of cell concentration in this work

Condensation d'ion sur une surface chargee analyse par dynamique moleculaire de la couche de Stern pour une interface eau-silice

National audienceNous etudions la couche de Stern a l'interface eau-silice chargee en calculant l'interaction ion-surface a partir de simulations de dynamique moleculaire biaisee de type umbrella-sampling [1] permettant ainsi de determiner les profils d'interaction des ions avec les surfaces d'ou decoulent les constantes d'association. Nous avons fait varier l'hydrophilicite d'une surface de silice en faisant varier le nombre de silanols en surface (Fig.1). Chaque surface comporte une charge unique portee par un oxygene deprotone qOc = -1 e

Food Technol. Biotechnol.

The oleaginous yeast Lipomyces starkeyi is interesting for industrial-scale production of biodiesel. Here it is reported that this yeast is able to digest unsaccharified, soluble potato starch. In these experiments, the cultivation time of Lipomyces starkeyi was reduced to half of the previously reported values. The effect of C:N molar ratio was studied on growth and lipid content of L. starkeyi in media containing glucose or potato starch as C-source. At a C:N molar ratio of 61.2 in glucose medium, the lipid content was measured at 30 % of the dry matter. It was established that the cellular lipid content increased with increasing C:N molar ratio, but the cell yield decreased. In a pH-controlled 1-litre agitated and aerated bioreactor, batch cultivation on glucose resulted in 23 % lipids in cells on dry mass basis (dm), cell yield of 0.25 g/g glucose, and lipid yield of 0.06 g/g glucose. Under the same operating conditions, fed-batch cultivation with discrete glucose additions resulted in 27 % lipids, cell yield of 0.28 g/g glucose, and lipid yield of 0.08 g/g glucose. On soluble but unsaccharified sweet potato starch, cell yield was 0.41 g/g glucose equivalent, lipid yield 0.16 g/g glucose equivalent, and lipid content in cells 40 %. The major fatty acids in the cells were C16:0 and C18:1 (accounting for 85–90 % by mass of the total lipids) with the rest being C16:1 and C18:0. All of these are valuable lipids for biodiesel production. Based on these results, wastes and wastewater from food industry and sewage sludge could serve as sources for the production of biodiesel. Key words: Lipomyces starkeyi, biodiesel, lipids, yeast, starch, fatty acid methyl esters Introduction Limited nature of fossilized resources and increasing concentration of greenhouse gases in our environment due to the indiscriminate use of fossil fuels have sparked a frantic race to harvest renewable resources to replace at least significant proportion of energy derived from fossil fuels. These efforts include utilization of solar, wind, hydro-, and geothermal energies. For the transportation sector, however, food industry and sewage sludge could serve as sources for the production of biodiesel

Condensation at a charged surface: a molecular dynamics investigation of the Stern layer for water-silica interfaces

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