The culture of Chlorella vulgaris in a recycled supernatant: Effects on biomass production and medium quality

► Productivity of Chlorella vulgaris was unaffected during medium recycling over 63 days. ► Organic matter excretion and accumulation by C. vulgaris was clearly observed. ► Molecular weight of excreted molecules ranged in two fractions: 1-3 kDa and > 40 kDa. ► The major excreted product (BP) was identified as polysaccharides in initial phase.