Optimization Of Culture Conditions For Chlorella In Biogas Slurry And Manufacture Of Duck Feed Additive Based On Chlorella

With the scale development of livestock and poultry industry,the discharge of livestock and poultry wastewater caused the soil,water and other environment pollutions,which has brought excessive loading for environment treatment.Microalgae as a unicellular lower eukaryote with high photosynthesis can make use of the NPK,trace elements and small organic molecules in the wastewater for growth metabolism,so as to remove nitrogen and phosphorus from wastewater and obtain the microalgae biomass.For those reasons above,treating organic wastewater by microalgae which is regarded as a new method has been studied widely by researchers.This study screened out coprophile microalgae which is adapted to organic sewage and utilized the coordinate symbiosis between microalgae and microbes for much more microalgae biomass.Therefore the optimal conditions for co-cultivation was figured out to increase the biological activity and growth rate of microalgae in the swine wastewater.The microalgae cultivated in the swine wastewater through proper pretreatment contained rich proteins,PUFA,all sorts of the functional polysaccharide and cytochrome.So in this study the obtained microalgae biomass was added into laying duck feed with eucommia powder and the effect of microalgae and eucommia on the egg production performance and egg quality was studied.The main results were as follow:Firstly the microalgae which was adapted to organic wastewater from pig farms was screened out.Than the strain was identified by morphology to be Chlorella sp.Meanwhile,the microbe which can coexist with Chlorella sp.was screened out from the effective microorganisms(EM)broth.The separation of bacteria and culture medium through centrifugation and than inoculation into the wastewater with chlorella separately further conformed the positive effect of bacteria on the growth of chlorella.The Chlorella in the presence of the best strain of bacterium broth synthesized chlorophyll as high as 7.586mg/L,and the chlorophyll content in the blank group was only 3.325mg/L.The best strain was identified as Lactobacillus by16 S rDNA sequence analysis.The standard curve based on the Chlorella dry weights and the absorbances of Chlorella suspension indicated that it rendered good linear relationship between the absorbance of algae suspension under 680 nm wavelength and the dry weight ofChlorella.So the absorbance can be used to symbolize the Chlorella growth state and figure out the algal biomass.The optimum co-culture conditions for the algae-bacteria combined system was achieved from the single factor experiments: pH=8.0,bacteria/algae=2:30 and culture temperature 30 ?.The corresponding algal biomass(algae dry weight)reached1.016g/L,1.028g/L,1.020g/L respectively.The results of orthogonal test indicated that Chlorella displayed the highest chlorophyll a content(4.650mg/L)after 6 days culturing under the combination of 25 ?,pH=7,44.88 mg or 2mL sugar and4:30(bacteria/algae)which was the best treatment for chlorophyll a,while 0.795g/L for Chlorella dry weight was obtained.In addition,temperature had the significant effect on the content of chlorophyll a in Chlorella cells.However,pH,the ratio of bacteria and algae,sugar cane molasses played little effects on the formation of chlorophyll a.Culture temperature,followed by pH,sugar cane molasses and the ratio of bacteria and Chlorella orderly,was the most influential factor in chlorophyll a yield.Through the comparison of consumption of glucose and content of forming chlorophyll a,the result showed that there was no direct linear relationship between the two,and when the culture temperature was 30 ? or above,the glucose in culture medium was consumed mostly by the bacteria.Fourier transform infrared spectroscopy(FTIR)was conducted to analyze the comparative contents of tree main compounds(carbohydrate,protein,lipid)in Chlorella cells obtained from different treatments.The result presented that the waveform of Chlorella was similar to each other,except the peak high at some wave numbers.After the light transmittance of Chlorella was standardized,it showed that under different combinations of temperature,pH,sugar cane molasses and bacteria/algae there was significant difference in carbohydrate comparative contents.The highest content of carbohydrate appeared in the combination of 25?,pH=8,67.32 mg sugar,30:2(algae/bacteria),which provides a reference for the orientation culture of Chlorella in the future study.But the overall efficiency of these factors had little influence on the protein and lipid relative contents.After 1% Chlorella powders and 2% equal amount of Chlorella and Eucommia powders were added into the basal diet of duck,the number of duck eggs,the total weight of eggs,the laying rate and the feed consumption did not show significant effection.however,the average weight of egg increased,with an increase of 3.8% in algae treatment and 0.7% in mixed group;Compared with the control group,the yolkcolor of duck eggs increased by nearly 3 Roche colorimetric units;The Haugh unit value was investigated in three groups,with 72.86 in algae group,76.94 in mixed group and 70.23 in control group,and the corresponding protein contents were12.36%,12.01%,11.71%,respectively.The results above indicated that the mix of algae and Eucommia leaf powders as a kind of duck feed additive could improve the yolk color,Haugh unit value of duck eggs and the content of eggs in different degree.Besides,compared with the control group,the cholesterol content in microalgae group and mixed group decreased by 14.87% and 21.15% respectively,which improved the eating quality of duck eggs.The feed-egg ratio in mixed group was 7.51,showing a decrease of 0.7% when compared with the control group.