Lactic Acid Production From Sugar Molasses And Glucose Waste Mother Liquid By Microbial Consortium CEE-DL15

Lactic acid was an important organic acid,widely used in food,chemical,cosmetic andpharmaceutical industries.In recent years,the shortage of oil resources and the white pollution problem increasingly prominent,represented by polylactic acid(PLA)biological macromolecule material,because of its good biodegradable properties,was regarded as a green alternative to plastic derived from oil.The application of PLA also drove the steady growth of the lactic acid market.However,high production costs had hindered the large-scale application of lactic acid and polylactic acid.The purpose of this study was to explore the efficient use of cheap waste biomass--sugar cane molasses and glucose crystallization waste mother liquor to produce lactic acid.Through exploring screening of microbial consortium,complex substrate metabolism and lactic acid production to reveal the mechanism of interaction in microbial consortium,which provide theoretical basis for the construction of artificial microbial consortium,the low cost and efficient production of lactic acid.First,microbial consortiums CEE-DL15 was screened out from stomach,which had Stability of fermentation and high yield of lactic acid.CEE-DL15 could utilize both monosaccharide(Glc,Fru,Xyl,et.al)and oligosaccharide(Suc,Malt,et.al),which accompanied by producing acid as well as gas.At the same time,it could utilize the nutrient-rich organic nitrogen source,and also could utilize the quick-acting inorganic nitrogen source.Genetic analysis found that CEE-DL15 was mainly composed of Clostridium sensustricto(57.29%),Escherichia(34.22%)and Enterococcus(5.32%).Secondly,the performance of lactic acid production by CEE-DL15 from sugar molasses was investigated.Under the condition of no-sterilization and molasses untreated,microbial consortiums CEE-DL15 grow well.Among the three fermentation medium evaluated,corn steep powder(CSLP)medium achieved the highest lactic acid productivity(2.31 g/L/h)and a little low lactic acid concentration and yield(83.24 g/L and 0.72 g/g,respectively),nitrogen source production cost saving 50-150%.The microbial consortium CEE-DL15 had a strong tolerance to untreated molasses,and could tolerate high concentration of molasses up to 500g/L.CEE-DL15 produced 112.34 g/L lactic acid,with a yield of 0.81 g/g,a maximum productivity of 4.49 g/L/h at initial sugarcane molasses of 350 g/L,which had a strong ability to transform untreated molasses into lactic acid.Economic analysis found that the sum of the three cost parameters(carbon source,nitrogen source and sterilization cost)was 2,935 ?/ton,accounting for 25-35% of the market price of the lactic acid market.Compared with glucose fermentation,the cost of raw materials was reduced by about 50%.The fermenting property of the microbial consortiums CEE-DL15 was better than that of single-bacterium E.coli DL-LA1501,E.faecalis DL-LA1520 and C.perfringei BNCC185933.Finally,the performance of lactic acid production by CEE-DL15 from glucose waste mother liquor was investigated.microbial consortiums CEE-DL15 could be used to produce lactic acid with cheap CSLP culture medium,and the fermentation process was nosterilization.CEE-DL15 produced 100.18 g/L lactic acid,with a yield of 0.83 g/g,a productivity of 1.67 g/L/h at initial glucose of 150 g/L from glucose waste mother liquor after recrystallization.Under the same conditions,the yield of lactic acid from glucose waste mother liquor befroe crystallized was reduced by 23.4%.Therefore,the Salt-CSLP medium was used instead of CSLP medium for fermentation,CEE-DL15 was able to grow rapidly under the Salt-CSLP medium,which produced 113.33 g/L lactic acid,with a yield of 0.91 g/g,a productivity of 1.42 g/L/h.In contrast,the yield of lactic acid and the productivity under the Salt-CSLP medium was significantly increased.The reason may be that compared with molasses,the solid nutrient composition of glucose waste mother liquor was simple,and the proper supplementation of inorganic salts would be conducive to improve the fermentation performance of CEE-DL15.In conclusion,microbial consortiums CEE-DL15 has high tolerance to crude substrate and high conversion efficiency form raw material.The production cost of lactic acid was greatly reduced by the efficient production of open batch fermentation without sterilization,reducing the energy consumption and complex operation of sterilization.