Chlorella across latitudes: investigating biochemical composition and antioxidant activities for biotechnological applications

With the present day rise of interest in acquiring sustainability in the pharmaceutical industry,there has been an emphasis on finding natural resources to replace the use of synthetic compounds used in products.Microalgae have garnered significant attention owing to their natural and sustainable capability to produce a diverse array of bioactive compounds.Therefore,this study aims to evaluate the biochemical composition and antioxidant properties of Chlorella strains from a tropical region(Chlorella UMACC 051 and Chlorella UMACC 038)and a polar region(Chlorella UMACC 250 and Chlorella UMACC 234).The cultures were grown for 10 d.At the end of the experiment,the specific growth rate,chlorophyll-a content,carotenoid content,biomass,and biochemical composition such as carbohydrate,protein and lipid content were determined.In addition,the phytochemical properties were determined using a total phenolic assay while the antioxidant activities were determined using 2,2-diphenyl-1-picrylhydrazyl(DPPH).Of all Chlorella strains tested,the tropical Chlorella UMACC 051 showed the fastest growth rate and biomass while the polar Chlorella UMACC 234 contained the highest pigment content and tropical Chlorella UMACC 038 has the highest total phenolic content.The biochemical composition analysis showed all strains have a high lipid content ranging from 45.36%to 60.30%dry weight.All Chlorella strains exhibited a small amount of antioxidant activity(15.42%to 30.15%)and total phenolic content ranging from 1.91±0.04 to 4.43±0.10 mg GAE·g–1 dry weight.The results indicated that polar Chlorella UMACC 234 has the most potential in containing significant amounts of bioactive compounds.

Growth and photosynthesis of Chlorella strains from polar,temperate and tropical freshwater environments under temperature stress

Elevated temperatures as a consequence of global warming have significant impacts on the adaptation and survival of microalgae which are important primary producers in many ecosystems. The impact of temperature on the photosynthesis of microalgae is of great interest as the primary production of algal biomass is strongly dependent on the photosynthetic rates in a dynamic environment. Here, we examine the effects of elevated temperature on Chlorella strains originating from different latitudes, namely Antarctic, Arctic, temperate and tropical regions. Chlorophyll fluorescence was used to assess the photosynthetic responses of the microalgae. Rapid light curves(RLCs) and maximum quantum yield( F_v/F_m) were recorded. The results showed that Chlorella originating from different latitudes portrayed different growth trends and photosynthetic performance. The Chlorella genus is eurythermal, with a broad temperature tolerance range, but with strain-specific characteristics. However, there was a large overlap between the tolerance range of the four strains due to their "eurythermal adaptivity". Changes in the photosynthetic parameters indicated temperature stress. The ability of the four strains to reactivate photosynthesis after inhibition of photosynthesis under high temperatures was also studied. The Chlorella strains were shown to recover in terms of photosynthesis and growth(measured as Chl a) when they were returned to their ambient temperatures. Polar strains showed faster recovery in their optimal temperature compared to that under the ambient temperature from which they were isolated.

Effects of the sunscreen ultraviolet filter,oxybenzone,on green microalgae

Ultraviolet(UV)filters are widely used in sunscreen and personal care products due to their ability to give protection to our skin from UV radiation.Oxybenzone,commonly known as benzophenone-3,is one type of UV filter found as the active ingredient in many pharmaceutical products.Although oxybenzone has been extensively studied as an environmental toxicant in the ecosystem,little is known about its toxicity effects on microalgae.The effects of oxybenzone on growth(measured as OD620 nm,chlɑand carotenoids)and macromolecular composition of polar microalgae(Chlorella UMACC 400 and Chlorella UMACC 401)and temperate microalgae(Chlorella sp.,Chlamydomonas reinhardtii,Scenedesmus quadricauda)were investigated.These microalgae were cultured in triplicate and exposed to different oxybenzone concentrations(0,100,200,300 and 400 mg·L-1),at 4℃and 18 for polar and temperate species respectively,for 96 h.The oxybenzone concentrations used℃represent a range from environmental to extreme concentrations to understand the impact of this toxicant on microalgae.The results showed that the highest concentration of oxybenzone(300 and 400 mg·L-1)had adverse effects on growth rate and biomass of these microalgae.However,exposure to oxybenzone concentrations ranging from 200 mg·L-1 to 400 mg·L-1 did not have significant effects on S.quadricauda growth.The exposure to oxybenzone at higher concentrations also led to changes in cell structure after 96 h.Generally,protein and carbohydrate content of all microalgae except S.quadricauda increased with increasing oxybenzone concentrations.Protein content increased significantly when cells were exposed to oxybenzone,though effects were greater in the polar species,suggesting that it could be one of the adaptive strategies that enabled these microalgae to tolerate oxybenzone.Further investigation is required to determine the effects of oxybenzone on other features of microalgal performance at relevant environmental concentrations.