Synergistic effects of arginine and calcium on astaxanthin and lipid accumulation in Haematococcus pluvialis under high light conditions

Abstract

Haematococcus pluvialis (H. pluvialis) is one of the richest natural sources of astaxanthin (AST). However, since the production of AST by H. pluvialis is unable to meet market demand, it is desirable to increase its productivity. This study provides an innovative strategy to improve astaxanthin and lipids productivity of H. pluvialis by combining arginine (Arg) and calcium (Ca²⁺) under 120 μmol m⁻² s⁻¹ light conditions. Application of Arg promoted astaxanthin and lipid accumulation by 25% and 24.5%, respectively. The co-supplementation of Arg and Ca²⁺ (0.25 mM Arg, 50 μM CaCl₂) further enhanced the astaxanthin and lipid productivity by 40.7% and 32.6% compared to the control. Arg and Ca²⁺ synergically activated the arginine metabolic pathway by triggering ornithine decarboxylase (odc), ornithine aminotransferase (oat), nitric oxide synthase (nos) and argininosuccinate lyase (asl) genes at both stages of cultivation, signifying their importance in growth and stress responses. More importantly, Arg and Ca²⁺ synergically controlled signaling molecules through the calcium channels and promoted astaxanthin and lipids by regulating carotenogenesis and lipogenesis. The results therefore provide a reference for research and application of Arg and Ca²⁺ in microalgae aquaculture.