Flavonoids are the secondary metabolites synthesized by microalgae and have diverse applications in various fields. The present study compares among two microalgal strains, Chlorella vulgaris (CV) and Chlorella pyrenoidosa (CP), for the production of flavonoids and lipids, which were cultivated in mixotrophic as well as autotrophic modes. This study also focuses on the role of l-phenylalanine as a supplement to enhance flavonoids. The current work establishes the relation between nitrates, external carbon, and l-phenylalanine for enhanced production of flavonoids and lipids. The extracted flavonoids were found to be maximum in CP-autotrophic mode followed by CV-mixotrophic mode with 138 μg/ml and 118 μg/ml, respectively. The common flavonoids observed with both the microalgal strains were quercetin, catechin, and p-coumaric acid. In comparison, the production of the maximum lipid of 23.7% was reported with mixotrophic operation in CV, followed by CP (19.4%). The scavenging activity of the extracted flavonoids was determined using a hydrogen peroxide assay and was found to be in the range of 63–73% at all experimental conditions. CP was found to produce more flavonoids in autotrophic mode, whereas mixotrophic mode showed maximum production of lipids and flavonoids in the CV. The simultaneous production of high value-added products, viz., flavonoids and lipids, not only paves a pathway for the biorefinery approach but also elevates the commercial potential during scale-up.

Graphical abstract

黄酮类化合物是微藻类合成的次生代谢产物，在各个领域都有不同的应用。本研究比较了两种小藻类菌株小球藻（CV）和小球藻小球藻（CP）的黄酮类和脂质的生产，这些菌株以混合营养和自养模式培养。该研究还集中于1-苯丙氨酸作为增强类黄酮的补充剂的作用。当前的工作建立了硝酸盐，外部碳和之间的关系升-苯丙氨酸可增强类黄酮和脂质的产生。发现在CP自养模式下提取的类黄酮含量最高，其次是CV混养模式，分别为138μg/ ml和118μg/ ml。在两个微藻菌株中观察到的常见类黄酮是槲皮素，儿茶素和对香豆酸。相比之下，在CV中混合营养操作的最大脂质产量为23.7％，其次是CP（19.4％）。提取的类黄酮的清除活性是用过氧化氢测定的，在所有实验条件下的清除率都在63-73％之间。发现CP在自养模式下产生更多的类黄酮，而混养模式显示CV中脂质和类黄酮的最大产生。同时生产高附加值的产品，即

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