The ability to produce high amounts of saturated fatty acids and monounsaturated fatty acids is particularly important in this context. Despite these preliminary successes and promising outlook for lipids produced from thraustochytrid algae, it is still necessary to develop flexible methods for downstream processing to enrich oils with a desired degree of saturation or unsaturation. It is also of interest to develop new products from these oils given the growing interest in their sustainable production. In this report, we address both of these issues through a sulfur-based reactive-processing of triglycerides produced in thraustochytrid microalgae. Specifically, sulfur was reacted with the mixture of the algae-derived triglycerides, forming a novel copolymer with the unsaturated triglycerides. The resulting polymer was analogous to related materials made from unsaturated plant oils, which have been used in a wide range of applications including heavy metal remediation, oil spill clean-up, PFAS capture, slow-release fertilisers, composite synthesis, cathode materials for Li-S batteries, 17 and thermal insulation. Accessing these materials through a new triglyceride source is therefore important, as it does not require access to plant oils otherwise used for food or those that require significant and detrimental land use. Additionally, the remaining saturated triglycerides that did not react with sulfur could be recovered in a significantly enriched form. This chemistry therefore also constitutes a novel method for separating saturated and unsaturated triglycerides produced in algae-an important capability for the downstream use of these triglycerides in food products and biodiesel production. Additionally, the process generates valuable sulfur polymers in the same step. Importantly, the low-cost and high abundance of sulfur bodes well for this method in terms of scalability and sustainability. The overall strategy is summarized in Figure .