Biochemical characterization of lipid metabolic genes of Aurantiochytrium limacinum.

Docosahexaenoic acid (DHA) is known to have numerous health benefits and immense dietary value. There is a pressing need to have a deeper understanding of DHA metabolism. Acyl CoA: Diacylglycerol Acyltransferase (DGAT) is an important enzyme of lipid anabolism and an essential piece of the puzzle. Aurantiochytrium limacinum, a primary producer of DHA, is a good model for studying DHA metabolism. Thus, we aimed to investigate important lipid metabolic genes from A. limacinum. We cloned four putative DGATs (DGAT2a, DGAT2b, DGAT2c, and DGAT2d) from A. limacinum and performed detailed in vivo and in vitro characterization. Functional characterization showed that not all the studied genes exhibited DGAT activity. DGAT2a and DGAT2d conferred DGAT activity whereas DGAT2b showed wax synthase (WS) activity and DGAT2c showed dual function of both WS and DGAT. Based on their identified function, DGAT2b and DGAT2c were renamed as AlWS and AlWS/DGAT respectively. DGAT2a was found to exhibit a preference for DHA as a substrate. DGAT2d was found to have robust activity and emerged as a promising candidate for genetic engineering aimed at increasing oil yield. The study enriches our knowledge of lipid biosynthetic enzymes in A. limacinum, which can be utilized to design suitable application strategies.

Extraction, fatty acid profile, phytochemical composition and antioxidant activities of fixed oils from spices belonging to Apiaceae and Lamiaceae family.

Fixed oil, the non-volatile fraction of oil from spices remains an unexplored entity. The study aimed to extract fixed oils from 13 Indian spices belonging to the Apiaceae and Lamiaceae family. Further fatty acid composition, antioxidant activities and phytochemical profile of the fixed oils was estimated. Among the studied spices, Ferula assa-foetida had the highest amount of fixed oil (19.93%). GC-MS profiling of the fixed oils showed palmitic, stearic, oleic, linoleic and alpha-linolenic to be the major fatty acids. The study further identified fixed oils from Trachyspermum ammi L., Petroselinum crispum L., Ocimum basilicum L. and Rosmarinus officinalis L. to be major source of protocatecheuic, 4,hydroxybenzoic, trans-cinnamic, myristein and trans-ferulic acid. R. officinalis, O. basilicum and Thymus vulgaris L. fixed oils also showed highest radical scavenging property. T. vulgaris, Majorana hortensis Moench. and O. Basilicum fixed oils confirmed high amounts of α-, ß + γ- and δ-tocopherol respectively. ß-sitosterol was found to be the dominating phytosterol in all fixed oils. Principal component analysis revealed existence of variation among spice fixed oils concerning to their fixed oil composition. The study thus identifies spice fixed oils as a rich source of lipid soluble bioactive compounds that are of tremendous industrial and pharmaceutical importance. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13197-021-05036-1.