Bioremediation of chromium(VI) and arsenic(III) using isolated microalgal (Chlorella thermophilia): Analysis of growth, biomolecular compositions (carbohydrate, protein, chlorophyll) and biosorption kinetics

Abstract

Microalgae are under research focus for the production of bio-fuels by bioremediation of different kinds of wastewater like industry and municipality and other sources. The current study deals with investigations towards the capability of isolated microalgae (Chlorella thermophilia) for the removal of Cr(VI) and As(III) by re-modeling their extracellular and intracellular compositions. This isolated microalgae was able to grow in the presence of Cr(VI) up to 1 mg L−1 concentration and As(III) up to 15 mg L−1 concentration. Carbohydrate content in microalgae increased to 28 % in 0.4 mg L−1 of Cr(VI) and 46 % in 10 mg L−1 of As(III) respectively as compared to control. The protein content of Chlorella thermophilia grown in Cr(VI) [1 mg L−1] and As(III) [15 mg L−1] containing media decreased by almost 61 % and 9 % respectively as compared to control. Growth kinetics results revealed the decline in biomass to 10 % and 15 % under exposure of Cr(VI) [0.6 mg L−1] and As(III) [10 mg L−1] respectively compared to control. Chlorella thermophilia showed the removal of As(III) within the range of 70–91 % [at an As(III) concentration of 0.5–10 mg L−1], while removal of Cr(VI) was within 50–65 % [at a Cr(VI) concentration of 0.2–0.6 mg L−1]. Interestingly, almost 60 % of Cr(VI) was removed within 6 days of microalgae growth while removal of As(III) was slow and steadily increased to 80 % in 30 days. Our results showed the prospects of Chlorella thermophilia as a sustainable resource for the removal of heavy metals [Cr(VI) and As(III)] from wastewater. In addition, the enrichment of carbohydrates in microalgae during their growth would be supportive for the production of biofuels.