Identification And Removal Of Inhibitor In Oleaginous Microalgae Medium

Microalgae have a wide range of potential applications in terms of bio-energy,environmental management and food and medicine.Aiming at the phenomenon that the accumulation of microalgae extracellular secretion in culture process leads to its growth inhibition,this study analyzed the composition of growth inhibitor accumulated in the culture medium of Chlorella vulgaris and Scenedesmus obliquus and investigated the inhibitor removal process.The result of C.vulgaris and S.obliquus cultivation with three-times-recycled medium showed that the growth rates continuously decreased and biomass accumulation reduced significantly with the prolonged incubation period and increased reusing times of medium.During the third time of reusing,the content of oil and chlorophyll a increased 26.0%and 16.0%,respectively,in C.vulgaris dry matter and 6.0%and 22.5%,respectively,in S.obliquus cells.The experiment of cultivating C.vulgaris and S.obliquus in the medium added with dichloromethane extracts and fatty acid standard products showed that the major components of inhibitors were C16:0 and C18 fatty acids.In addition,there was a significant effect on the growth and the intracellular organism of C.vulgaris and S.obliquus when the fatty acids accumulated to more than 20 mg/L.To remove the fatty acids in the medium effectively,the adsorbent was screened from strongly alkaline anion exchanger,HY-M2001 and D262,macroporous adsorbent resin,X-5,D4006,AB-8,S-8 and NKA-?.The result showed that HY-M2001 and D262 could impact the content of nutrient and pigment in the medium significantly,causing the loss of nutrients.NKA-? had the strongest adsorption capacity to the fatty acids with the removal ratios in the medium of.vulgaris and S.obliquus being 46.2%and 39.3%,respectively,while no significant effect on the content of carbohydrates,pigments,ions,etc.In addition,X-5 and S-8 had obvious adsorption to pigments,while S-8 had a strongest adsorption capacity to carbohydrates and poor adsorption capacity to fatty acids relatively.Experiments using the recycled medium treated by macroporous adsorbent resin NKA-?,showed the growth of C.vulgaris and S.obliquus could be improved with the specific growth rate increasing by 61.44%and 68.10%,respectively,and reaching 92.7%and 89.9%of fresh medium group.The static adsorption experiments of NKA-II to free fatty acids in the medium of C.vulgaris and S.obliquus was optimized by single factor and orthogonal experiments.Results showed the effect factors on the adsorption of fatty acids should be in the order of temperature,pH,shaking time and ratio of adsorbent to medium.And the best combination was temperature 15 ?,pH 9,shaking time 4 h,ratio of adsorbent to medium 1:10.In the optimized conditions,the removal rate of fatty acids in the medium of C.vulgaris and S.obliquus treated by NKA-? was 62.47%and 66.34%,respectively.