Biological activities and plant growth regulators producing from some microalgae biomass cultivated in different wastewater concentrations

• Published in: Biomass conversion and biorefinery 2023-06, Vol.13 (9), p.8075-8088
• Main Authors: Elakbawy, Walaa M., Shanab, Sanaa M. M., Shalaby, Emad A.
• Format: Article
• Language: English
• Subjects: Acetic acid; Aeration; Algae; Anabaena; Antimicrobial agents; Antioxidants; Ascorbic acid; Biotechnology; Chlorella; Cultivation; Energy; Fungicides; Growth regulators; Lichens; Luminous intensity; Media; Nostoc; Original Article; Renewable and Green Energy; Treated sewage; Wastewater treatment
• ISSN: 2190-6815; 2190-6823
• DOI: 10.1007/s13399-021-01610-x

The present study aimed to evaluate the growth parameters and biological activities of two cyanobacterial and a chlorphyta species cultivated on BG110 and BG11 (as control media) respectively, as well as a combination of culture media (BG) with treated sewage wastewater (TSW) at various concentrations (100, 75, and 50% TSW) which were selected from six algal species (three cyanobacterial and three chlorophyta species) according to the concentration of auxins and cytokinins analyzed by HPLC. The experiments were conducted in triplicates and cultures were incubated at 25 ± 1 °C under continuous aeration and light intensity of 40µE/m2/s for 30 days. The Biological activities include antimicrobial (using agar well diffusion assay) and antioxidant (using DPPH radical methods) of absolute methanol extracts were evaluated. The obtained results revealed that maximum growth of the studied algal species on their specific culture media (BG11 and BG110) showed variable growth which was significantly enhanced when cultivated in combined media (BG11 or BG110 with TSW). HPLC analysis of auxin (IAA, indol acetic acid) and cytokinin (BA, benzyl adenin) in the investigated algal species grown under different media composition showed large variations depending on algal species and the type of culture media used. Maximum IAA concentration was recorded in Chlorella vulgaris and Nostoc muscorum cultivated in 100% TSW media. Concerning BA (cytokinin), Chlorella vulgaris and Nostoc muscorum showed the highest relative percentages on cultivation in 100% TSW. The antioxidant activity results of the algal species Nostoc muscorum cultured on BG110 showed higher activity with IC50 45.46 ug/ml when compared with Anabaena oryzae and Chlorella vulgaris (47.71 and 46.13 ug/ml), while IAA, BA, BHT (butylated hydroxytoluene), and ascorbic acid showed (26.97, 28.08, 13.19, and 13.34 ug/ml). The cultivation of Chlorella vulgaris on 100% TSW showed the highest antioxidant activity with IC50 33.99 ug/ml, while Anabaena oryzae showed 35.33 ug/ml on 50% TSW and Nostoc muscorum 39.30 ug/ml on 75% TSW. Concerning the cultivation of Chlorella vulgaris under nitrogen stress conditions, the highest antioxidant activity (IC50) was recorded under 0 × N2 and 0.5 × N2 (30.91 and 33.77 ug/ml). The antimicrobial activity showed that IAA and BA exhibited antibacterial activity against both Gram -ve and Gram + ve bacteria in addition to antifungal activity for Candida albicans only.