Growth optimization, free radical scavenging and antibacterial potential of Chlorella sp. SRD3 extracts against clinical isolates

Abstract

Aim The aim of present work was to explore the potential of Chlorella sp. SRD3 extracts for antioxidant and antibacterial activity along with the evaluation of minimum inhibitory concentration (MIC) and haemolytic activity to detect RBC cell damage. Methods and Results Screening and isolation of microalgae was performed using bold basal medium under normal illuminance (at 27°C) and microscopic observation. Growth of the microalgae was optimized using a different medium and light source. The isolated microalgae incubated under fluorescent light when cultured in F/2 medium showed a highest dry biomass yield of 3·77 ± 0·1 g l−1, when compared to the growth under direct sunlight (2·74 ± 0·07 g dwt l−1). The quantitative analysis of extracts revealed higher phenols, flavonoids and proanthocyanidins in ethyl acetate and hexane extracts followed by methanol. The antioxidant activity of extracts was tested against 1‐diphenyl‐2‐picrylhydrazyl and ABTS radical, its reducing power assay was performed. From antibacterial activity, the two extracts showed better inhibition against Gram‐negative bacteria. Also, they resulted in very low MIC values with effective activity against pathogens. In haemolytic activity, no haemolysis occurred, when the concentration (µg ml−1) was below 64 for methanol and 32 for ethyl acetate extract. In addition, Chlorella sp. extracts were characterized by GC‐MS analysis to detect the major compounds. Conclusion The polar extracts revealed satisfactory results against the clinical isolates and the compounds responsible were reflected in the GC‐MS spectrum. Significance and Impact of the Study The present study revealed significant biological potentials of the green alga, Chlorella sp. such as antioxidant, antibacterial and hemolytic activities. Therefore, this vital source might serve as a cost‐effective, alternative choice to the pharmaceutical and food industries in the near future.

Unveiling antimicrobial activity of microalgae Chlorella sorokiniana (UKM2), Chlorella sp. (UKM8) and Scenedesmus sp. (UKM9)

“…Extract from Chlorella sp. was very effective as antibacterial agent against S. aureus, E. coli, B. subtilis and B. cereus, which have been noted previously by ( Kellam and Walker, 1989 , Salem et al, 2014 , Santhosh et al, 2019 , Thamilvanan et al, 2016 ). Among genus Scenedesmus , the inhibition effect of ME from S. obliquus was found active against E. coli , B. cereus , and S. aureus with an inhibition zone between 9 and 9.7 mm ( Marrez et al, 2019 ).…”

Active and phenolic compounds in Spirogyra sp. PDNA1 is an antibiotic for some bacteria and fungi

“…The effect of phenol on the fungi used in the study was recorded by the phenolic methanolic extract, the highest percentage of inhibition against (Candida albicans) was with a diameter of (26) mm, and the least inhibition was against the fungus (Aspergillus niger) with a diameter of (20) mm, and the phenolic hexane extract had the highest inhibition against (Candida albicans) fungus, with a diameter of (26) mm, and the lowest inhibition rate was in (Aspergillus niger), with a diameter of (18) mm. The Inhibition diameters higher than the crude extract of algae indicated that it affected its pure isolated form better than it was mixed with the rest of the materials and components, which reduces its effect and concentration in the concentration used against bacteria, and this result was consistent with a study [25].…”

Total Phenolic Content, Biomass Composition, and Antioxidant Activity of Selected Marine Microalgal Species with Potential as Aquaculture Feed

“…The combined TPC (the sum of TPC of aqueous and methanolic extracts) in all the species examined (6–12 mg GAE g −1 DW) was in some cases lower [ 53 , 54 , 55 , 56 ], similar [ 8 , 11 , 17 , 48 , 49 , 52 , 56 , 57 ], or higher [ 11 , 14 , 15 , 17 , 48 , 49 , 55 , 58 ] than previously reported values. In practical terms, the phenolic content of 5.1–6.85 mg GAE g −1 DW presented by N. oculata and T. lutea was ten times higher than that of herbs like rosemary, sage, and mint (0.5–0.6 mg GAE g −1 DW) [ 59 ] but lower than that of agri-food waste products like grape vines, tomato waste and grapefruit waste, which have a high phenolic content (32 mg GAE g −1 DW for dried grape vines) and strong antioxidant capacity [ 60 ].…”