Continuous versus batch production of lipids in the microalgae Acutodesmus obliquus.

This work provides a novel quantitative comparison of batch versus continuous microalgal lipid production in the wild type and starchless mutant strain of Acutodesmus obliquus. Both strains showed higher TAG yields on light under batch operation compared to continuous nitrogen limitation. The starchless mutant showed 0.20gTAGmolph-1 for batch and 0.12gTAGmolph-1 for continuous operation, while the wildtype only showed 0.16gTAGmolph-1 for batch and 0.08gTAGmolph-1 for continuous operation. Also, higher TAG contents were found under batch starvation (26% of dry weight for the wildtype and 43% of dry weight for starchless mutant) compared to continuous cultivations (16% of dry weight for the wildtype and 33% of dry weight for starchless mutant). Starch acts as the favoured storage metabolite during nitrogen limitation in A. obliquus, whereas TAG is only accumulated after starch reaches a cellular maximum of 40% of dry weight.

Draft Genome Sequence of the Oleaginous Green Alga Tetradesmus obliquus UTEX 393.

The microalgae Tetradesmus obliquus is able to maintain a high photosynthetic efficiency under nitrogen limitation and is considered a promising green microalgae for sustainable production of diverse compounds, including biofuels. Here, we report the first draft whole-genome shotgun sequencing of T. obliquus The final assembly comprises 108,715,903 bp with over 1,368 scaffolds.

Survey data on key climate and environmental drivers of farmers' migration in Burkina Faso, West Africa.

This article describes two datasets generated from various sources in south western Burkina Faso to identify the key climate and environmental drivers that cause farmers to migrate. The survey sampling is random but reasoned and rational. The first dataset from 367 farm households contains data on farmers' perception of climate change risks or hazards, their impacts on farmland productivity and farm households' risk management strategies. The second dataset from 58 farm households contains data on agricultural practices, environmental changes, and environmental migration. Three supplemental Excel sheets show the results of the surveys. Details on the sample as well as further interpretation and discussion of the surveys are available in the associated research article ('Field Facts for Crop Insurance Design: Empirical Evidence from South Western Burkina Faso' (W. M. Fonta, S. Sanfo, B. Ibrahim, B. Barry, 2015) [1]).

pH-upshock yields more lipids in nitrogen-starved Neochloris oleoabundans.

This study explores the influence of alkaline pH and light intensity on the performance of Neochloris oleoabundans in two-stage batch cultivation: a first stage for nitrogen-sufficient growth followed by a second stage for lipid accumulation under nitrogen starvation. The highest TAG yield on absorbed light was obtained at low light conditions when pre-cultivation occurred at pH 8 and lipid accumulation was induced at pH 10. However, a higher alkaline pH by itself appears not to enhance the starvation-induced increase in lipid contents, except when combined with high light and pre-cultivation occurs at those same conditions. Such strategy however also results in low biomass and TAG yields on absorbed light. Fatty acid composition analysis revealed that the relative fatty acid contents of the TAG pool are nevertheless independent from the light intensity and pH applied at either cultivation stage, suggesting a high specificity of N. oleoabundans cell machinery towards TAG production.

Edible oils from microalgae: insights in TAG accumulation.

Microalgae are a promising future source for sustainable edible oils. To make microalgal oil a cost-effective alternative for common vegetable oils, increasing TAG productivity and TAG content are of high importance. Fulfilling these targets requires proper understanding of lipid metabolism in microalgae. Here, we provide an overview of our current knowledge on the biology of TAG accumulation as well as the latest developments and future directions for increasing oil production in microalgae, considering both metabolic engineering techniques and cultivation strategies.

Growth of oil accumulating microalga Neochloris oleoabundans under alkaline-saline conditions.

The effect of elevated pH and salt concentration on the growth of the freshwater microalga Neochloris oleoabundans was investigated. A study was conducted in 24-well plates on the design of a growth medium and subsequently applied in a photobioreactor. An artificial seawater medium with reduced Ca(2+) and PO(4)(3-) could prevent mineral precipitation at high pH levels. Growth was characterized in this new medium at pH 8.1 and at pH 10.0, with 420 mM of total salts. Specific growth rates of 0.08 h(-1) at pH 8.1 and 0.04 h(-1) at pH 10.0 were obtained under controlled turbidostat cultivation. The effect of nitrogen starvation on lipid accumulation was also investigated. Fatty acids content increased not only with nitrogen limitation but also with a pH increase (up to 35% in the dry biomass). Fluorescence microscopy gave visual proof that N. oleoabundans accumulates oil bodies when growing in saline conditions at high pH.

Influence of the rate of contrast change on the quality of contrast sensitivity assessment: a comparison of three psychophysical methods.

Criterion-free forced-choice procedures for measuring contrast sensitivity with a cathode ray tube (CRT) have low within-subject, intersubject, and test-retest variabilities, but a long test time compared with psychophysical methods that rely on the subject's criterion to determine threshold. Test time and variability of criterion-dependent methods depend on the rate at which the contrast changes on the CRT display. This study compared two criterion-dependent psychophysical methods for measuring contrast sensitivity (the method of increasing contrast and the von Békésy tracking method) with a criterion-free two-alternative forced-choice procedure. A range of rates of contrast change was studied: 0.1, 0.3, 0.5, 0.7 and 1.0 log unit s-1. Contrast sensitivity, within-subject variability, intersubject variability, test-retest variability, and test time of the three methods were compared. The 2-AFC procedure performed best with regard to within-subject, intersubject, and test-retest variabilities. A time-efficient alternative was the von Békésy tracking method at rates between 0.1 and 0.5 log unit s-1.