Effects of elevated temperatures on growth and photosynthetic performance of polar Chlorella

Global warming has been the subject of concern in today’s world with elevating temperature causing the melting of polar ice and increasing sea level.The aim of this study was to investigate the physiological and photosynthetic performance of two polar Chlorella,namely Chlorella UMACC 250 and Chlorella UMACC 234 to elevating temperatures as might be experienced under future warming scenarios.The cultures were exposed to three different temperatures of 4℃,8℃and 12℃.The growth and photosynthetic activity were determined every 2 d for a period of 10 d.At the end of the experiment,the cultures were harvested and analysed for biochemical composition.Both Chlorella strains were able to tolerate higher temperatures than their ambient temperature.The final pigments content showed an increasing trend with increased temperatures for both strains.The photosynthetic activities were measured using pulse-amplitude modulation(PAM)fluorometer.The photosynthetic parameters including maximum quantum efficiency(Fv/Fm),maximum relative electron transport rate(r ETRmax),light harvesting efficiency(a)and photoadaptive index(Ek)were derived from the rapid light curves(RLCs).Both Chlorella strains showed a slight decline in growth and photosynthetic activities at the initial part of the experiment.However,they showed the ability to recuperate with Chlorella UMACC 250 recovers better compared to Chlorella UMACC 234.Both Chlorella strains showed similar trend in their carbohydrate content at 12℃,while the protein content of Chlorella UMACC 234 decreased when exposed to increasing temperatures.The results indicated that polar Chlorella are able to survive at increased temperatures throughout the experiment.

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.

Anisotropic transport of microalgae Chlorella vulgaris in microfluidic channel

In this work, we study the regional dependence of transport behavior of microalgae Chlorella vulgaris inside microflu- idic channel on applied fluid flow rate. The microalgae are treated as spherical naturally buoyant particles. Deviation from the normal diffusion or Brownian transport is characterized based on the scaling behavior of the mean square displacement （MSD） of the particle trajectories by resolving the displacements in the streamwise （flow） and perpendicular directions. The channel is divided into three different flow regions, namely center region of the channel and two near-wall boundaries and the particle motions are analyzed at different flow rates. We use the scaled Brownian motion to model the transitional characteristics in the scaling behavior of the MSDs. We find that there exist anisotropic anomalous transports in all the three flow regions with mixed sub-diffusive, normal and super-diffusive behavior in both longitudinal and transverse directions.

Microbial reduction of graphene oxide and its application in microbial fuel cells and biophotovoltaics

Despite more than a decade of study,there are still significant obstacles to overcome before graphene can be successfully produced on a large scale for commercial use.Chemical oxidation of graphite to produce graphene oxide(GO),followed by a subsequent reduction process to synthesize reduced graphene oxide(rGO),is considered the most practical method for mass production.Microorganisms,which are abundant in nature and inexpensive,are one of the potential green reductants for rGO synthesis.However,there is no recent review discussing the reported microbial reduction of GO in detail.To address this,we present a comprehensive review on the reduction of GO by a range of microorganisms and compared their efficacies and reaction conditions.Also,presented were the mechanisms by which microorganisms reduce GO.We also reviewed the recent advancements in using microbially reduced GO as the anode and cathode material in the microbial fuel cell(MFC)and algal biophotovoltaics(BPV),as well as the challenges and future directions in microbial fuel cell research.

Inhibitory activities of microalgal extracts against Epstein-Barr virus DNA release from lymphoblastoid cells

This study aimed to assess the inhibitory activities of methanol extracts from the microalgae Ankistrodesmus convolutus,Synechococcus elongatus,and Spirulina platensis against Epstein-Barr virus(EBV) in three Burkitt's lymphoma(BL) cell lines,namely Akata,B95-8,and P3HR-1.The antiviral activity was assessed by quantifying the cell-free EBV DNA using real-time polymerase chain reaction(PCR) technique.The methanol extracts from Ankistrodesmus convolutus and Synechococcus elongatus displayed low cytotoxicity and potent effect in re-ducing cell-free EBV DNA(EC50<0.01 μg/ml) with a high therapeutic index(>28 000).After fractionation by column chromatography,the fraction from Synechococcus elongatus(SEF1) reduced the cell-free EBV DNA most effectively(EC50=2.9 μg/ml,therapeutic index>69).Upon further fractionation by high performance liquid chromatography(HPLC),the sub-fraction SEF1'a was most active in reducing the cell-free EBV DNA(EC50=1.38 μg/ml,therapeutic index>14.5).This study suggests that microalgae could be a potential source of antiviral compounds that can be used against EBV.