The　efficient　treatment　and　energy　recovery　from　salvaged　microalgae　have　been　imperative　considering　both　environmental　and　economic　concerns.　Herein,　this　study　proposed　a　biotechnological　platform　for　converting　microalgae　into　medium-chain　fatty　acids　(MCFAs)　through　anaerobic　fermentation　as　well　as　exploring　the　roles　of　different　electron　donors　(EDs).　After　exploring　various　ED　combinations,　the　results　suggested　that　a　single　ED,　especially　sole　ethanol　stimulation,　exhibited　more　pronounced　stimulation　effects　on　MCFA　production　compared　to　those　of　the　hybrid　ED　stimulations.　Furthermore,　ethanol　and　lactic　acid　served　as　the　basis　for　the　formation　of　longer-chain　alcohols　and　odd-chain　fatty　acids　in　the　liquid　fermentation　products,　respectively.　The　dynamics　and　thermodynamics　analyses　confirmed　the　distinctions　in　the　accumulation　trends　and　saturated　compositions　of　main　products　under　different　ED　compositions.　Moreover,　mechanistic　investigations　revealed　that　differences　in　chain　elongation　efficiency　of　ethanol　and　lactic　acid　and　in　the　genome-based　metabolic　potential　for　the　microbial　systems　contributed　to　the　intricate　feedback　regulations　of　biochemical　reactions　in　different　microalgae　fermentation　scenarios.　Overall,　this　study　provided　valuable　insights　for　sustainable　energy　conversion　of　microalgae　by　orienting　toward　the　recovery　of　high-value　biochemicals,　serving　as　a　theoretical　basis　for　the　selection　and　optimization　of　ED　before　industrial　application.　©　2024　American　Chemical　Society.