Xiang Wang,Zhong-Hong Zhang,Kuan-Kuan Yuan,Hui-Ying Xu,Guo-Hui He,Libin Yang,Joseph Buhagiar,Wei-Dong Yang,Yalei Zhang,Carol Sze Ki Lin,Hong-Ye Li
Microalgae-based antibiotic removal treatment has attracted attention because of its low carbon and sustainable advantages. The microalgal co-metabolism system with a suitable carbon source leads to enhanced performance of pollutant removal. However, currently, limited knowledge is available for the removal of fluoroquinolone using a microalgae-mediated co-metabolism system. In this study, we first investigated that the biotic processes by alga Haematococcus lacustris in the co-metabolism system by adding glycerol would be the main contributors responsible for the removal of 10 mg/L ofloxacin (OFL) with the efficiency of 79.73% and the removal of 10 mg/L enrofloxacin (ENR) with the efficiency of 54.10%, respectively. Furthermore, we found that pyruvate from glycerol was converted into substrates and precursors, thereby resulting in the significant accumulations of microalgal astaxanthin and lipid. The astaxanthin content of H. lacustris was achieved at 4.81% and 4.69% treated with OFL and ENR in the presence of glycerol, with 16.04% and 14.55% of lipid content, respectively. The proposed metabolites and pathways were identified to plausibly explain the biodegradation of fluoroquinolone by H. lacustris . The molecular analyses demonstrated that cytochrome P450 (CYP450) enzymes are responsible for the biodegradation of fluoroquinolone, and it was further verified that fluoroquinolones might insert into CYP450 to finally form an efficient and tight binding conformation by molecular dynamic simulation. These findings provide a microalgae-based route for feasible and sustainable biodegradation of antibiotics using a co-metabolism strategy comprising glycerol as a carbon source, with the synergistic accumulation of valuable products.
Dopamine (DA) has attracted attention because of its effects on Haematococcus lacustris biomass, astaxanthin production, and physiological responses. The alga treated with 25 μM DA combined with 1 g L –1 sodium chloride exhibited 7.63 %, 41.25 %, and 52.04 % increases in biomass (1.41 g L –1 ), astaxanthin content (32.37 mg/g), and astaxanthin productivity (3.51 mg L –1 d –1 ) respectively, compared with the salinity stress and high light. Exogenous DA treatment promoted lipid synthesis while reducing carbohydrate and protein contents. Moreover, carotenogenesis and lipogenesis-associated genes were upregulated under DA induction. Inhibition of reactive oxygen species and autophagy, along with mitogen-activated protein kinase activation, promoted astaxanthin accumulation under DA. Furthermore, DA application boosted astaxanthin biosynthesis by regulating the levels of respiratory metabolic intermediates, the γ-aminobutyric acid shunt, and important phytohormones. These findings present a potential and successful biotechnological approach for enhancing biomass and astaxanthin production in H. lacustris under stressful conditions.
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