Study On The Enzymatic Production Of Maltose Syrup At High Concentration Substrate

In order to reduce cost of maltose syrup production,one of the most effective ways was to improve concentration of substrates,which was benefit to increase the solid content of production and save energy.However,the increase of initial concentration usually has a negative effect on the enzymatic efficiency.In addition,the DE value must be strictly controlled,which leads to further increase of viscosity.Therefore,it is necessary to study the effect of concentration and DE value of liquefied liquid on the saccharification,and to explore the production technology of high maltose syrup at high concentration substrate.In this paper,maltose syrup was produced by hydrolyzing maltodextrin with β-amylase.Firstly saccharification conditions were optimized,and effects of substrate concentration and DE value on the enzymatic efficiency were investigated.Then saccharification with compound enzymes was established,and the maltose yield was improved by two-step hydrolysis and pullulanase pretreatment.Lastly the product composition was analyzed.The main contents are attached as follows:(1)The effect of substrate concentration and DE value on the saccharification at high concentration was investigated.In terms of concentration,the maltose yield reached the peak(62.76%),but the maltose concent was only 134.98 mg/mL,when the initial maltodextrin concentration was 20%.When the initial concentration was 50%,the maximum maltose content was 291.01 mg/m L,but yield decreased to 54.21%.This showed that increasing the substrate concentration could effectively increase the solid content of production and the enzymatic efficiency needs to improve further.In terms of DE value,maltose yield increased first and then decreased.When the DE value was less than 15,maltodextrin had larger molecular weight with more content of long chain and greater viscosity during saccharification,which resulted in lower enzymatic efficiency.However,when the DE value was more than 15,maltodextrin had low molecular weight and more content of short chain,resulting in more byproducts.Therefore,the concentration was determined as 50% and DE value was 15,with 30% and 45% as a control.(2)Effects of compound enzymes(β-amylase and pullulanase)on saccharification at high concentration and mechanisms were investigated.After the addition of pullulanase was 4 ASPU/g,addition mode of compound enzymes was optimized.Although compound enzymes could increase maltose yield,the addition modes increased differently.The maltose yield was increased by 32.34% and to 71.62%,when pullulanase was added after β-amylasis for 8 h.β-amylase could not hydrolyze the α-1,4 glycosidic bond cauase side chain was too short.At this time,the addition of pullulanase could effectively hydrolyze the α-1,6 glycosidic bond,which was conducive to synergistic effect of two enzymes.(3)In order to further improve the synergistic effect of compound enzymes,two-step hydrolysis was put forward.The processing conditions could be as follow: 50% maltodextrin solution(50 °C,pH 5.0)was added to β-amylase for 8 h(first stage);heated to 60 °C,and then pullulanase was added to continue to reaction for 48 h(second stage).The yield of maltose was increased by 9.86% to 78.68%.After adding pullulanase,the increasing rate of oligosaccharide chain content of different DP values was greater,the increasing rate of small-molecule sugar content was smaller,and the dispersion coefficient increased less.So pullulanase debranching reaction might be the main reaction to avoid competition of compound enzymes on space position near the branch,which was more conducive to the maltose accumulation.(4)In order to further reduce the competition of compound enzymes on space position,the pullulanase pretreatment was used to hydrolyze the branching point.After 2 h of pullulanase treatment,content of oligosaccharide chains reached highest.The branch point of maltodextrin decreased and β-amylase hydrolysis rate was higher.This indicated that the maltodextrin treated by pullulanase for 2 h was more suitable for the production of maltose,and the yield of maltose reached 80.55%.(5)The product composition was analyzed,and the result showed that the product contained glucose,maltose,maltotriose and maltotetraose.The maltodextrin solution(DE 10)could improve the yield of maltose by two-step hydrolysis and pullulanase pretreatment,and the maltose content decreased to about 19%.In addition,compared with the reported results,two-step hydrolysis and pullulanase pretreatment could achieve saccharification at high concentration,save energy and shorten the production cycle.Besides,the product yield and product composition could meet the industrial requirements,showing obvious superiority.