| Starch wastewater is a typical food processing effluent with high concentration of organic matters including starch and protein.Direct disposal of these wastewaters will significantly deteriorate the environment.Microalgae-based wastewater treatment methods have attracted increasing interest in recent years due to their capacity to effectively remove and recycle contaminants in wastewater.However,starch wastewater is difficult to be directly utilized by microalgae due to its extremely high concentration of organic matters which exist in a complex form.It must be pre-treated before used for microalgae cultivation,which greatly complicates the production process,Furthermore,the small size of microalgal cells makes microalgae harvesting difficult.This significantly increases the cost of wastewater treatment and limits its application in wastewater treatment.Regarding above issues,this study developed a new process of one-step culture and harvesting of high value-added biomass coupled with starch wastewater treatment by microalgae and fungi based on the synergistic effect of microalgae and fungi.Based on the rich hydrolytic enzymes secretion,excellent biosecurity and absorption capacity,the synchronous cultivation and harvesting of high value-added biomass was achieved combined with the efficient wastewater treatment.The main results achieved are as follows:(1)Aspergillus niger and Aspergillus oryzae were chosen as candidate fungi,to be co-cultured with Chlorella pyrenoidosa for the treatment of starch wastewater.Cell growth,nutrients removal,and microalgae harvesting efficiency in different so-culture systems were measured to identify the best combination.When C.pyrenoidosa was co-cultured with either spores or pellets of A.niger,algal cells were gradually died with the sharp decrease of pH.The result indicated that A.niger was not suitable as the co-culture fungus for the synergistic treatment of starch wastewater.C.pyrenoidosa grow well when co-cultured with A.oryzae.However,algal cells could not be completely harvested when co-cultured with A.oryzae pellets.C.pyrenoidosa and the spores of A.oryzae,both algal and fungal cells grew well in the PSW.In addition,algal cells could be completely harvested by the fungal pellets after cultured for 72 h.The starch wastewater became clear.In summary,co-culture C.pyrenoidosa with the spores of A.oryzae was determined to be the best co-culture strategy.(2)The key parameters of the co-culture process,the inoculation amount of the two microorganisms and the light intensity,were optimized to achieve high nutrients removal efficiency and biomass yield.Results indicated that the optimum inoculation size of algal cells and fungal spores were 40,000 and 10 mL-1,respectively.In addition,light intensity of 30 μmol/m2/s was favorable for both biomass accumulation and nutrients removal.Under the optimized conditions,the final biomass of the co-culture system reached 3.53 g/L,and the proportion of algae in the algae-fungi consortia complex attained 47.57%.Meanwhile,the removal efficiency of the main pollutants of starch wastewater,COD,TN and TP was above 80%.(3)The performance of the developed co-culture in starch wastewater treatment and synchronously cell culture and harvesting was thoroughly studied.The results showed that the biomass yield and pollutant removal in the co-culture system were much higher than that of individual culture of either microalgae or fungi.The dry biomass weight in the co-culture system reached 3.53 g/L.Meanwhile,the synergistic effects between microalgae and fungi greatly improved the removal efficiencies of main pollutants,as the removal efficiency of COD,TN,and TP reached 92.08,83.56,and 96.58%,respectively.In addition,the color and odor of wastewater were also significantly reduced.Furthermore,with the germination of fngal spores and the formation of fungal pellets,algal cells were gradually attached to fungal pellets and could be completely harvested by the fungal pellets after 72 h.(4)The algae-fungi consortia could be simply collected by filtration.The algae-fungi consortia were homogenous and structurally intact.The protein content of the algae-fungi consortia was 54.30%and contained 16 kinds of amino acids.The essential amino acid content occupied 37.8%of the total amino acids content.It could be used as high-quality protein feedstock for animal feed.In addition,the lipid content of the algae-fungi consortia reached 28.10%.The percentage of essential fatty acids,such as linoleic acid and linolenic acid,was quite high which account for 66.27%of the total fatty acid content.It can be used as an excellent raw material for the production of high-value health care products.In summary,a novel method of one-step co-cultivation and harvesting of microalgae and fungi,for efficient starch wastewater treatment and high-value biomass production was developed.This process significantly simplified the treatment of starch wastewater and effectively reduced treatment of wastewater costs.This study provided a new way for the efficient treatment of food processing wastewater,which had practical significance for the development of green biotechnology with microalgae as the core. |
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