Abstract

The current study examined the effect of walnut shell extracts (WSE) on simultaneous astaxanthin and lipid production by Haematococcus pluvialis under abiotic stress . After supplementation with 15% WSE, the contents of astaxanthin and lipids were enhanced by 77.57% and 23.39%, respectively, compared with the control. The chlorophyll, carbohydrate and protein contents decreased, and the transcription levels of carotenogenic and lipogenic genes, as well as the levels of the reactive oxygen species (ROS), glutathione (GSH) and light‑oxygen-voltage histidine kinase (LOV-HK), all increased. Further investigation showed that LOV-HK regulated astaxanthin and lipid biosynthesis by mediating carotenogenesis, lipogenesis and ROS signalling. Overall, the present study demonstrated that microalgae cultivation coupled with walnut shell recycling is an effective strategy for hyper-accumulation of astaxanthin and lipids and that there is a pivotal interaction between LOV-HK and ROS in WSE-induced regulation of astaxanthin and lipid synthesis in H. pluvialis .