Using the hydrolysate of Chinese medicine residues as nutrient source improves the performance of oil-producing...

The development of microalgae-based biofuels has long been a research focus for achieving green and sustainable development. Chinese medicine residues, an abundant organic waste rich in cellulose, hemicellulose, lignin, proteins, polysaccharides, and microminerals, offer scalable feedstock. Here, their hydrolysate (HCMR) was used as an additional nutrient source for cultivating oil-producing algae. The hydrolysate promotes the growth and productivity of oil-producing algae such as Chlorococcum sp., Tribonema aequale, and Scenedesmus sp., while also indicating its feasibility for scaling up Scenedesmus sp. cultivation. The HCMR addition increased biomass by 1.58-fold and fatty‑acid content by 1.27‑fold relative to BG11 medium. Analysis of the fatty acid composition in Scenedesmus sp. confirmed that the addition of hydrolysate from Chinese medicine residues significantly increased the proportions of high-quality fatty acids, including palmitoleic acid (C16:1) and oleic acid (C18:1), while reducing the proportions of linoleic acid (C18:2) and α-linolenic acid (C18:3), thereby improving the cetane number and oxidative stability of the biodiesel. Metabolomics analysis reveals potential regulatory pathways by which HCMR enhances lipid accumulation in Scenedesmus sp., implicating transamination in glutamate metabolism and offering a sustainable route for utilizing similar organic waste as an additional source of nutrients in oil-producing microalgae cultivation.