Antimicrobial and Antioxidant Potential of Scenedesmus obliquus Microalgae in the Context of Integral Biorefinery Concept

Small-scale photobioreactors (PBRs) in the inoculum stage were designed with internal (red or green) and external white LED light as an initial step of a larger-scale installation aimed at fulfilling the integral biorefinery concept for maximum utilization of microalgal biomass in a multifunctional laboratory. The specific growth rate of Scenedesmus obliquus (Turpin) Kützing biomass for given cultural conditions was analyzed by using MAPLE software. For the determination of total polyphenols, flavonoids, chlorophyll “a” and “b”, carotenoids and lipids, UHPLC-HRMS, ISO-20776/1, ISO-10993-5 and CUPRAC tests were carried out. Under red light growing, a higher content of polyphenols was found, while the green light favoured the flavonoid accumulation in the biomass. Chlorophylls, carotenoids and lipids were in the same order of magnitude in both samples. The dichloromethane extracts obtained from the biomass of each PBR synergistically potentiated at low concentrations (0.01–0.05 mg/mL) the antibacterial activity of penicillin, fluoroquinolones or oregano essential oil against the selected food-borne pathogens (Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) without showing any in vitro cytotoxicity. Both extracts exhibited good cupric ion-reducing antioxidant capacity at concentrations above 0.042–0.08 mg/mL. The UHPLC-HRMS analysis revealed that both extracts contained long chain fatty acids and carotenoids thus explaining their antibacterial and antioxidant potential. The applied engineering approach showed a great potential to modify microalgae metabolism for the synthesis of target compounds by S. obliquus with capacity for the development of health-promoting nutraceuticals for poultry farming.

Complete wastewater discoloration by a novel peroxidase source with promising bioxidative properties

BACKGROUND Our study aimed to characterize and prospect immobilization strategies for a novel fungal peroxidase - POD (EC 1.11.1.7) and to insert it in the context of pollutant remediation, since these compounds pose risks to human and environmental health. The enzymatic extract was obtained by submerged fermentation of the fungus Trichoderma koningiopsis in an alternative substrate, consisting of fresh microalgal biomass. The immobilization efficiency was evaluated by monitoring the residual activity (RA) and the discoloration potential (DP) of a synthetic dye solution. Concomitantly, the catalytic properties of free POD were explored, and the most promising storage strategy to maintain the enzymatic activity was studied. RESULTS The novel guaiacol peroxidase expressed specific activity of up to 7801 U mg−1 in the free form, showing stability when subjected to up to 80°C in a pH range between 4.0-8.0. Furthermore, the bioproduct immobilized on magnetic nanoparticles expressed up to 689% RA and 100% DP. An increase in the RA of the enzyme, both in free and immobilized form, was also observed after storage for up to 8 months. The synthesized magnetic nanozymes showed good reusability, maintaining 13546 U mg−1 after ten cycles and removing 94% of color in a second batch. Toxicological evaluation with Allium cepa indicated that the enzymatic process of color removal with immobilized POD was essential to eliminate genotoxic effects. CONCLUSION T. koningiopsis peroxidase production and immobilization presented in our work are promising for the enzyme market and for the wastewater treatment technologies, considering its high bioxidative potential.

Production of Microalgal Biomass at Different Growth Phases to Use as Biofuel Feedstock

The growth of microalgae under optimized conditions was determined for assessing their growth rate and biomass production. In this study, the growth of both green algae (Chlamydomonas noctigama and Chlorella vulgaris) and cyanobacteria (Anabaena variabilis and Nostoc spongiaeforme) was measured as optical density. Chlamydomonas noctigama and Chlorella vulgaris showed the doubling time of 9.5 and 8.0 hours, respectively, whereas Anabaena variabilis and Nostoc spongiaeforme showed the doubling time of 14.8 and 16.6 hours, respectively. All the species exhibited the highest growth in terms of biomass at the phase in between stationary and death phases. J. Asiat. Soc. Bangladesh, Sci. 47(2): 161-171, December 2021