High throughput quantitative volatile profiling of melons with silicone rod extraction - thermal desorption - GC-MS for plant breeding line selection.

Volatile compounds determine the aroma of fruits, giving their unique flavor characteristics. The aim of many plant breeding projects is to improve the consumers' flavor experience when eating fresh produce. Large scale breeding trials produce thousands of samples which need volatile profiling amongst other phenotypes. Despite this interest, current methods have limitations: sampling unsuitable for field conditions, high cost and the inherent issue of highly variable data, which can hinder interpretation. We introduced a simple and robust sampling methodology based on silicone rod extraction, thermal desorption gas chromatography - mass spectrometry (GC-MS) to address these issues. We used differentiated calibration standards to generate quantitative data for metabolites of varying abundance. The method was used to profile 327 melons with high sensitivity (0.05-10 ng/mL, compound dependent), good reproducibility (7%) and differentiate melon varieties based on their volatile profile. The data were then used for line selection for a desired flavor profile.

Extraction of lipids from microalgae using CO2-expanded methanol and liquid CO2.

The use of CO2-expanded methanol (cxMeOH) and liquid carbon dioxide (lCO2) is proposed to extract lipids from Botryococcus braunii. When compressed CO2 dissolves in methanol, the solvent expands in volume, decreases in polarity and so increases in its selectivity for biodiesel desirable lipids. Solid phase extraction of the algal extract showed that the cxMeOH extracted 21 mg of biodiesel desirable lipids per mL of organic solvent compared to 3mg/mL using either neat methanol or chloroform/methanol mixture. The non-polar lCO2 showed a high affinity for non-polar lipids. Using lCO2, it is possible to extract up to 10% neutral lipids relative to the mass of dry algae. Unlike extractions using conventional solvents, these new methods require little to no volatile, flammable, or chlorinated organic solvents.

Determination of antifungal proteins in soil by liquid chromatography.

A liquid chromatography method was developed for the determination of antifungal/antimicrobial proteins Rs-AFP1 and Dm-AMP1 in sandy loam soils. The extraction of these highly basic proteins was achieved by mechanical shaking with aqueous Tris buffer pH 9 containing guanidinium thiocyanate salt (4.1 M), EDTA and nonionic polyoxyethylene 20 cetyl ether, Brij-58 detergent. The extracts were cleaned up on Oasis HLB polymer solid-phase extraction cartridges and quantified by liquid chromatography fluorescence detection based on the fluorescence properties of the tryptophan content of these proteins. The detector response was linear for 0.3-10 microg mL(-1). Procedural recoveries were tested in the range 10-100 mg kg(-1). The limit of quantification was 10 mg kg(-1 )protein in the soil sample representing the lowest validated fortification level. The antifungal proteins were found to be stable in soil extract tested up to 9 days when stored at 4 degrees C.