Supplementation of exogenous phytohormones for enhancing the removal of sulfamethoxazole and the simultaneous accumulation of lipid by Chlorella vulgaris.

In this study, the phytohormone gibberellins (GAs) were used to enhance sulfamethoxazole (SMX) removal and lipid accumulation in the microalgae Chlorella vulgaris. At the concentration of 50 mg/L GAs, the SMX removal achieved by C. vulgaris was 91.8 % while the lipid productivity of microalga was at 11.05 mg/L d-1, which were much higher than that without GAs (3.5 % for SMX removal and 0.52 mg/L d-1 for lipid productivity). Supplementation of GAs enhanced the expression of antioxidase-related genes in C. vulgaris as a direct response towards the toxicity of SMX. In addition, GAs increased lipid production of C. vulgaris by up-regulating the expression of genes related to carbon cycle of microalgal cells. In summary, exogenous GAs promoted the stress tolerance and lipid accumulation of microalgae at the same time, which is conducive to improving the economic benefits of microalgae-based antibiotics removal as well as biofuel production potential.

Promoting effect of plant hormone gibberellin on co-metabolism of sulfamethoxazole by microalgae Chlorella pyrenoidosa.

In this study, sodium acetate (NaAC) as a co-substrate effectively promoted the metabolism of sulfamethoxazole (SMX) by microalgae Chlorella pyrenoidosa. In the cultivation supplied with 5.0 and 10.0 g L-1 NaAC, 51.1% and 61.2% SMX was removed, respectively. On this basis, the improvement effect of plant hormone gibberellin (GA3) on SMX removal by 5 g L-1 NaAC supplied as co-substrate was further investigated. The results showed that biodegradation played decisive role in the removal of SMX. As a plant hormone, GA3 effectively improved the co-metabolic removal efficiency of SMX by C. pyrenoidosa. Especially when GA3 dosage reached 10.0 and 50.0 mg L-1, C. pyrenoidosa showed a very high SMX removal rate of 83.5% and 95.3%, respectively. Transcriptome analysis showed that GA3 promoted the removal of SMX by C. pyrenoidosa was the result of the combined action of exogenous and endogenous plant hormones.