Adaptability Analysis Of Three Chlorella Strains From Different Regions In Response To Enviromental Factors

Among the oleaginous microalgae,Chlorella is thought to be a promising candidate due to its high photosynthetic efficiency,lipid productivity and fast growth ability.These microalgae can occupy extreme habitats ranging from desert soil to the polar region and able to adapt to a variety of environmental conditions.However,there are a few researches on comparing the response of Chlorella strains from different geographical regions to dynamic environmental factors,especially for the lipid productivity.In this research,three Chlorella strains from arctic glacier(Chlorella-arc).desert soil(Chlorella-Des)and temperate native lake(Chlorella-Nat)were isolated and identified as Chlorella sp.,C.sorokiniana and C.sorokiniana,respectively.The growth,biochemical composition,lipid content and fatty acid composition of each strain cultured under the modes of diurnal temperature fluctuations and day-night cycles were compared.In addition,the optimal factors(diurnal temperature fluctuation,day-night cycle&C/N)of lipid accumulation for each strain were investigated.The main results were described as follows:(1)All the three Chlorella strains showed desirable abilities of accumulating lipid under diurnal temperature fluctuations and day-night cycles.Their fatty acid profiles were suitable for biodiesel production,although the growth and biochemical composition were seemed to be region-specific.The highest lipid content was at 51.83±2.49%DW,42.80±2.97%DW and 36.13±2.27%DW under different temperature fluctuation of 21?/10?,28?/3?,28?/21?,respectively.(2)Chlorella-Arc could grow well under the lower temperature,and was the most tolerant strain in response to extreme day-night cycle.Chlorella-Des was the most tolerant strain in response to diurnal temperature fluctuation and had the highest photosynthetic capacity.Chlorella-Nat was the most sensitive strain in response to dynamic environmental factors and might reduce the potential contamination from outcompeting organisms by quick growing.(3)Diurnal temperature fluctuation,day-night cycle and C/N were optimized for lipid productivity of three Chlorella strains by RSM.All the RSM modes were selected suitable since their lack of fit was not significant.The optimum culture environment conditions were obtained as below:diurnal temperature fluctuation 21?/15?,day-night cycle 12h/12h,C/N(5.0mmol/L)/(0.317mmol/L)for Chlorella-Arc;28?/15?,12h/12h,(5.0mmol/L)/(0.562mmol/L)for Chlorella-Des and 28?/28?,19.4h/4.6h,(5.0mmol/L)/(0.607mmol/L)for Chlorella-Nat.Under above optimal cultural conditions,the maximal lipid productivity reached as 140.62mg·L-1·day-1,158.23mg·L-1·day-1 and163.28mg·L-1·day-1,respectively.