Laminaria Japonica hydrolysate as a novel biostimulant for enhancing DHA accumulation in Aurantiochytrium limacinum.

Aurantiochytrium limacinum is recognized as an ideal candidate to produce docosahexaenoic acid (DHA). However, elevating the biomass and lipid yield on a large scale is still a challenge. In this study, a simple and feasible strategy for enhancing DHA accumulation based on Laminaria japonica hydrolysate (LPH) addition has been developed. The addition of 40 mL/L LPH enhanced the accumulation of biomass and lipid of A. limacinum by 31.48% and 49.48%, respectively. Meanwhile, the DHA production was increased by 40.78%. By investigating the effects on DHA and biomass accumulation hormones in LPH, gibberellin 3, abscisic acid, and salicylic acid were characterized as the key factor. With the addition of LPH, the upregulated genes were enriched in pathways including fatty acid biosynthesis, metabolism, and the tricarboxylic acid cycle. In particular, key genes involved in fatty acid synthesis, such as ACC1 and FAS2, were significantly upregulated. In this study, LPH was identified as a novel additive with practical application value due to its readily available and low-cost raw ingredients.