Mechanisms of Sodium-Acetate-Induced DHA Accumulation in a DHA-Producing Microalga, Crypthecodinium sp. SUN.

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (PUFA) that is critical for the intelligence and visual development of infants. Crypthecodinium is the first microalga approved by the Food and Drug Administration for DHA production, but its relatively high intracellular starch content restricts fatty acid accumulation. In this study, different carbon sources, including glucose (G), sodium acetate (S) and mixed carbon (M), were used to investigate the regulatory mechanisms of intracellular organic carbon distribution in Crypthecodinium sp. SUN. Results show that glucose favored cell growth and starch accumulation. Sodium acetate limited glucose utilization and starch accumulation but caused a significant increase in total fatty acid (TFA) accumulation and the DHA percentage. Thus, the DHA content in the S group was highest among three groups and reached a maximum (10.65% of DW) at 96 h that was 2.92-fold and 2.24-fold of that in the G and M groups, respectively. Comparative transcriptome analysis showed that rather than the expression of key genes in fatty acids biosynthesis, increased intracellular acetyl-CoA content appeared to be the key regulatory factor for TFA accumulation. Additionally, metabolome analysis showed that the accumulated DHA-rich metabolites of lipid biosynthesis might be the reason for the higher TFA content and DHA percentage of the S group. The present study provides valuable insights to guide further research in DHA production.

Optimization and characterization of curcumin loaded in octenylsuccinate oat ß-glucan micelles with an emphasis on degree of substitution and molecular weight.

The dependence of the curcumin loading capacity (CLC) of octenylsuccinate oat ß-glucan (OSG) micelles on the structural parameters (degree of substitution, DS; molecular weight, Mw) of OSG was unknown and explored in this study. Meanwhile, the curcumin-loaded OSG micelle (COM) was first characterized. The results from response surface methodology revealed that the linear effects of Mw and stirrer input power, as well as the quadratic effect of DS, were significant (p < 0.05). The maximum CLC value of the OSG micelle was obtained as 4.21 µg/mg. Dynamic light scattering showed that the average size and ζ potential of the COM were 308 nm and -10.8 mV, respectively. Transmission electron microscopy and atomic force microscopy evidenced that the COM was elliptical in shape. Fourier transform infrared spectroscopy, differential scanning calorimeltry, and X-ray diffraction revealed that curcumin was loaded in OSG micelles in an amorphous form by interacting with OSG molecules.

Retention of iceberg lettuce quality by low temperature storage and postharvest application of 1-methylcyclopropene or gibberellic acid.

This study was conducted to evaluate the changes in quality of iceberg lettuce during storage at different temperatures and the effects of postharvest treatments of 1-methylcyclopropene or gibberellic acid at high temperature. The results showed that quality of the lettuce was remarkably retained during storage at 0 °C, but significantly declined at 20 °C. However, quality of the vegetable at shelf-temperature (20 °C, 85 ~ 95% RH) was effectively delayed by the treatment with 1-methylcyclopropene (1-MCP) or gibberellic acid (GA). Browning of the lettuce leaves was significantly inhibited by the storage at low temperature and by treatment with1-MCP and GA. The biochemical analysis further indicated that the reduction of soluble protein and sugar, decrease in activity of polyphenol oxidase (PPO) and peroxidase (POD) and accumulation of free amino acids in the lettuce leaves during storage could be remarkably prevented by low temperature, treatment with1-MCP or GA. Our result suggested that 1-MCP or GA treatment would provide a potential way for controlling quality of the lettuce under suboptimal postharvest temperature conditions.