Study On Preparation Of Galacturonic Acid By Hydrolysis Of Sunflower Heads Pectin

As a functional monosaccharide,the galacturonic acid is widespread applicable in medicine,food and chemical engineering.Due to the low production of the existing galacturonic acid preparation process,the product is difficult to purify.This problem limits the industrial production of galacturonic acid.Sunflower head pectin is a natural low-ester pectin,which is rich in galacturonic acid.So it is a superior raw material to prepare the galacturonic acid.The present paper focuses in the exploration of the process,which can simply and efficiently prepare and separate galacturonic acid,through chemical and biological approaches using sunflower heads as raw materials.Proposed strategies may provide theoretical basis for industrial productions.The research content and detailed results are as follows:（1）According to the method which is established by the laboratory,we prepared a high content of HG sunflower pectin.Sunflower heads were extracted by 0.2%oxalic acid and then sunflower heads pectin（AHP）was obtained with a yield of 11.34%.The content of sugar,uronic acid,ash and the degree of esterification of AHP was 71.4%,60.1%,3.1%and 31.8%respectively.The molecular weight was 7 k Da.HPLC results showed that the AHP was consisted of Gal A（82.2%）,Rha（7.1%）,Glc（2.1%）,Gal（4.2%）and Ara（4.4%）.In conclusion,AHP was rich in homogalacturonan（HG）domain with a low molecular weight and low degree of esterification,which was a suitable raw material for preparing Gal A.（2）The optimization of preparation processes to galacturonic acid.We designed six processes for preparing Gal A by combining alkaline de-esterification,enzymatic hydrolysis,acid hydrolysis,ethanol precipitation and other methods.Taken full account of the Gal A yield,purity,operation simplicity and production cost,we determined the optimal preparation process.AHP was firstly de-esterified at 0.05 M Na OH for 1 h at room temperature and then the de-esterified product solution（D-AHP）was obtained.The p H of D-AHP solution was adjusted 7 using HCl and then desalted the solution by 3,000 Da hollow fiber cartridge.D-AHP was enzymatic hydrolyzed by acidic liquid pectinase（CAS:9032-75-1）for 8 h.The enzymatic liquid was boiled and centrifugalized,and then the supernatant（D-E-AHP）was attained.Used the hollow fiber cartridge to isolate the galacturonic acid.The galacturonic acid product（D-E_H-AHP）can be obtained from the ultrafiltrate with a yield of 80.7%.Product was consisted of 99%Gal A.（3）Hundred grams-preparation of galacturonic acid product:Used the above optimized process,we repeated for three times with 100 g AHP as raw material.Results showed that the preparation process was repeatable and easy to operate.The average yield of galacturonic acid product was 79.83%and the variable coefficient was 2.32%.The average content of Gal A was 98.85%and the variable coefficient was0.82%.The sugar content and uronic acid content of galacturonic acid product was99.1%and 85.8%without nucleic acids,proteins,pigments and other impurities.The product was high purity galacturonic acid without other detectable oligogalacturonic acid from FT-IR,MS and ¹³C NMR techniques.The degree of esterification of the product was 0%.In summary,proposed Gal A preparation strategies may hold great promise for a theoretical reference for industrial production.