Human milk fat substitutes (HMFSs) are the structured lipids intended for infant formula. It provides energy and essential fatty acid for infant. HMFSs are mainly prepared by enzymatic method. In this study, we aim to explore the potential for producing HMFSs by fermentation using R. opacus. The results indicated that different compounds with chain length from 12 to 18, used as carbon source, could be incorporated into triacylglycerols directly. Polyunsaturated fatty acids in term of ARA, EPA, DHA could enter the kennedy pathway directly and involved in the biosynthesis of triacylglycerols. GC, UPLC-MS and ¹³C-NMR analysis demonstrated that typical structured lipids β-OPL (40.09%) was synthesized in R. opacus. Transcriptome analysis revealed that β-oxidation, fatty acid elongation and kennedy pathways existed in R. opacus. It was concluded that fatty acid supplied as carbon source could enter the kennedy pathways directly or via the de novo fatty acid biosynthesis pathway depending on the chain length, thus, affect the triacylglycerol species formed in the Rhodococcus opacus.

人乳脂肪替代品（HMFS）是旨在用于婴儿配方食品的结构化脂质。它为婴儿提供能量和必需脂肪酸。HMFS主要通过酶法制备。在这项研究中，我们旨在探索通过使用不透明芽孢杆菌发酵生产HMFS的潜力。结果表明，可以将链长为12至18的不同化合物用作碳源，直接将其引入三酰基甘油中。ARA，EPA，DHA等多不饱和脂肪酸可直接进入肯尼迪途径，参与三酰甘油的生物合成。GC，UPLC-MS和¹³ C-NMR分析表明，典型的结构化脂质β- OPL（40.09％）是在不透明红球菌中合成的。转录组分析表明，在R. opacus中存在β-氧化，脂肪酸延伸和肯尼迪途径。得出的结论是，作为碳源供应的脂肪酸可根据链长直接或通过从头脂肪酸生物合成途径进入肯尼迪途径，从而影响不透明红球菌中形成的三酰基甘油种类。