Preparation Of Propyl Gallate And Ethanol Fermentation By Acorn

Acorn(Quercus L.),which contains a large amount of starch,cellulose,lipid and tannin,is a high-quality starch-based raw material.In addition,the acorn tannin has pharmacological activities,such as antibacterial,antioxidation and antiinflammatory.Composition of acorn tannin is complicated and was easily decomposed.Therefore,it is necessary to establish a preparation process of propyl gallate to increase the added value of acorn.In this study,a three-stage countercurrent extraction of acorn tannin was established.Under the optimal conditions(solid-liquid ratio 1:10(g/mL),60?,3 h),the extraction efficiencies of acorn kernel and shell tannin were 72.21%and 75.72%,respectively.Comparing the concentration efficiency of tannin by organic solvent and precipitation methods,the optimum conditions for the precipitation method were as follows:tannin and saturated calcium hydroxide ratio was 2:5(v/v),pH 12.3.After 30 min,the precipitate of calcium-tannin was centrifuged and dissolved by phosphoric acid(pH<3).The concentration efficiency of acorn tannin was 79.43%.It has been determined that the concentrated wastewater contains 11%ethanol,which can be reused for the extraction process to replace the consumption of pure water.The extraction efficiencies of the acorn kernel and shell tannin were 69.92%and 74.73%,respectively,which are similar to the original process.Then,preparation of propyl gallate technology by acorn tannin was explored.The optimal conditions for the enzymatic method of propyl gallate were as follows:tannin and n-propanol ratio was 1:5(g/mL),tannase 200 mg,50? for 24 h.PG yield was only about 47%.The chemical method of propyl gallate can be divided into two-step esterification and one-step transesterification.(1)Two-step esterification:under alkaline hydrolysis conditions(tannin and NaOH mass ratio 1:1,110?,2 h)and enzymatic hydrolysis conditions(tannase 200 mg,pH 5,40?,4 h),gallic acid conversion was 38.58%and 55.22%,respectively.Mixed with hydrochloric acid to catalyze the esterification at 100? for 10 h,propyl gallate conversion was only 30.43%.(2)One-step transesterification:under the optimal conditions:acorn tannin,n-propanol and phosphoric acid catalyst ratio was 4:20:1(g:mL:g),100? for 14 h,PG yield was 79.12%.The experiment proves that the one-step transesterification process is more help to produce the by-products of acorn tannin,so as to realize high value utilization in the industry.In summary,conversion of PG in the process of acorn tannin extraction and propyl gallate preparation was about 45%.That is,the yield of propyl gallate is 22.5 mg/g acorn.Finally,the process of ethanol production by acorn starch was improved.Enzymatic saccharification with a-amylase 0.15 KNU/g,glucoamylase 1.5 AGU/g and tannase 0.20 U/g at 60? for 1 h,and fermentation at 32? for 72 h,ethanol yield was 87 g/L.Based on Aspen Plus,a model of co-production process about propyl gallate and ethanol was established.It is planned to consume 100,000 t of acorn per year,which can produced propyl gallate 1,813.7 t and fermented ethanol 26,000 t.According to strict material balance and energy consumption analysis,the water consumption in this process is about 20.8 t,the wastewater volume is about 21.3 t,and the process energy consumption is about 9.93×107 kJ/h.