Salting-out And Sugaring-out Extraction Of Carboxylic Acids And Coupling Fermentation

Carboxylic acids are predominant platform compounds and biobased intermediates,which can be produced through biotransformation from various renewable resources.Due to the high hydrophilicity and low concentration of carboxylic acids,by-products and impurities in the fermentation broths,the downstream separation process is complex,which makes the separation operation become the bottleneck of the large-scale production of carboxylic acids.Therefore,the development of economical and high-efficient separation technology is the key to solve the problem.In view of the above problems,salting-out extraction was used to separate carboxylic acids from fermentation broths based on previous research.Binodal curves of different salting-out extraction systems were plotted to explore its regularity and characteristics.The partition behaviors of short chain carboxylic acids in different salting-out extraction systems were studied systematically.The effects of system composition,temperature and pH on the partition behaviors of carboxylic acids were investigated The partition rules of carboxylic acids in different systems were summarized.Finally,salting-out extraction was applied to separate succinic acid from fermentation broths.Considering the recovery and recycling of inorganic salts in salting-out extraction systems,sugaring-out extraction coupled fermentation of lactic acid production was developed.The results are as follows:(1)It was found that the phase forming ability of organic solvents is proportional to their hydrophobicity by plotting binodal curves of different salting-out extraction systems.Clog P is more suitable than permittivity to analyze the phase forming ability of organic solvents in salting-out extraction systems.With the increase of hydrophobicity of organic solvents,hydrophobicity interaction gradually dominates in the two-phase system,which weakens the influence of salting-out effect of inorganic salts on phase forming.(2)The partition behaviors of fifteen kind of carboxylic acids in different salting-out extraction systems were investigated.It was found that,the higher hydrophobicity of carboxylic acids were,the easier were be extracted into solvent phase.However,the hydrophobicity of organic solvents is not completely related to the partition behaviors of carboxylic acids.Salting out extraction of carboxylic acids is not suitable under alkaline conditions.The extraction efficiency of carboxylic acids by ammonium sulfate system much better than potassium hydrogen phosphate system.Ethanol/potassium hydrogen phosphate system has the highest separation coefficients for different carboxylic acids,while acetone/ammonium sulfate system has the highest extraction efficiency.(3)By investigating the partition behaviors of seven monocarboxylic acids in four monoalcohols/potassium hydrogen phosphate systems,it was found that the more hydrophilicity of organic solvents and more hydrophobicity carboxylic acids were,the higher extraction efficiency.With the increase of tie line length,the partition coefficient of carboxylic acids with higher hydrophobicity increases faster,the partition coefficient of carboxylic acids with higher hydrophilicity decreases faster.Under certain system composition,the natural logarithm of the partition coefficient(In K)of carboxylic acids is 3-D correlated with Clog P of carboxylic acids and monohydric alcohol;under the same salting-out extraction system,the natural logarithm of the partition coefficient(In K)of carboxylic acids is 3-D correlated with the tie line length and the methyl number of carboxylic acids.The partition coefficients of monocarboxylic acids in any system can be calculated.Salting-out extraction of carboxylic acids is an exothermic process,the increasing of temperature will decrease the extraction efficiency of carboxylic acids.Under alkaline conditions,the partition coefficient,phase ratio and recovery of carboxylic acids were decreased with the increase of pH.Compared with the ammonium sulfate system,pH has no significant effect on the partition behaviors of carboxylic acids.(4)Salting-out extraction system of acetone/ammonium sulfate and crystallization were combined to recover succinic acid from fermentation broths.It was found that,the partition behaviors of carboxylic acids was significantly affected by pH,undissociated carboxylic acids was apt to extract into solvent phase.The fermentation broths can be salting-out extraction directly without filtration,succinic acid was extracted into the upper phase and 99.04%of cell and 90.82%of proteins could be removed simultaneously.Acetone can be recovered by distillation,ammonium sulfate can be recovered by dissolution crystallization with methanol.The total recovery(64.44%)and purity(90.58%)of succinic acid were obtained through salting-out extraction,activated carbon adsorption,vacuum distillation and crystallization drying.(5)It was found that dimethyl sulfoxide,methanol and ethanol are can't form sugaring-out extraction system with glucose in sugaring-out extraction system by plotting binodal curves.The phase forming ability of organic solvents was:acetonitrile>tetrahydrofuran>tert-butanol>n-propanol>acetone>isopropanol.The phase forming ability of non-proton solvents is stronger than proton solvents alcohols.The higher phase forming ability with higher number of hydroxyl groups.Under the same hydroxyl groups number,monosaccharides with 6-sided ring have higher phase forming ability than 5-sided ring structure.Hexose with axial-OH(4)and equatorial-OH(2)are more hydrated than those with equatorial-OH(4)and either equatorial or axial-OH(2),which in turn are more hydrated than sugars bearing axial-OH(4)and axial-OH(2).Therefore,D-galactose has the strongest phase forming ability.Temperature has little effect on the binodal curve of isopropanol/glucose system,but the increase of temperature will cause the binodal curve position of acetonitrile/glucose system to move up and the phase formation range to become smaller.(6)Sugaring-out extraction system of isopropanol/glucose coupling fermentation to produced lactic acid.The partition coefficient(1.39)and recovery(84.27%)of lactic acid were obtained by a system composed of 12%(w/w)glucose and 40%(w/w)isopropanol.The isopropanol has strong inhibition on Lactobacillus rhamnosus,the concentration of isopropanol should be controlled below 10 g/L.The nutritional composition of raffinate was insufficient after diluted with water,and residual lactic acid and isopropanol results in yield and production of lactic acid reduced greatly by re-inoculation and fermentation.The yield and production of lactic acid were similar to normal fermentation when yeast powder was added in the raffinate.In summary,by investigating the partition behaviors of different carboxylic acids in different salting-out extraction systems,the partition rules of carboxylic acids were summarized,which deepened the understanding of the application of salting-out extraction system and helped to provide guidance for other substances of salting-out extraction.Aiming at the recovery and recycling of inorganic salts in the salting-out extraction system,sugaring-out extraction system was developed and applied to separate lactic acid successfully.The method avoids the problem of the recycling of soluting-out agent,which helped to reduce resource waste and waste water discharge.It provides a new idea for coupling fermentation and separation of bio-based chemicals.