Docosahexaenoic acid (DHA) is one of the essential polyunsaturated fatty acids required for human health. Recently Schizochytrium sp. has become an ideal microorganism for the industrial production of DHA due to its advantages of easy cultivation, fast growth rate, simple fatty acid composition and high DHA content. This review focuses on the new progress about DHA extraction from Schizochytrium sp. Current efforts about the screening and improvement of Schizochytrium sp., optimization of the fermentation, lipid extraction and DHA purification were discussed. Meanwhile, the different routes involved in DHA synthesis in Schizochytrium sp. were described. At last, we propose that breeding of stable high DHA-yielding Schizochytrium sp., exploring low-cost and high-efficiency fermentation substrates, and clarifying DHA synthesis pathways are the future research priorities.

Flame-retardant polymer nanocomposites exhibiting remarkably improved flame-retardant and environmentally friendly properties have been widely utilized to replace traditional halogenated fire retardants. In this review, flame retardant mechanisms of polymer nanocomposites such as barrier effect, char formation, three-dimensional nanostructure, and radical trapping, are discussed to explain how nanomaterials can be incorporated in a polymer to reduce the polymer’s flammability. Properties that are critical in governing the flame-retardant mechanisms of polymer nanocomposites are discussed in this review. Specifically, category, surface property, and concentration of nanomaterials are critical in affecting flame-retardant properties of polymer nanocomposites and are reviewed in detail. Nanocomposite categories, especially, silicates (clays), inorganic hydroxides, carbonaceous materials, metal oxides, polysilsequioxanes, and their combinations are well described. The use of synergism and surface modification of nanomaterials are important strategies for optimizing flame retardancy of polymer nanocomposites. The peak heat-release rate (HRR), the most important parameter for predicting fire hazard, is widely involved in this review.