不同酸水解条件下葡聚糖生成糠醛类化合物的规律性

Production of Furfural Compounds from Dextran under Different Acid Hydrolysis Conditions

首先采用HLB固相萃取柱富集酸水解产物中的糠醛类化合物并结合超高效液相色谱,建立同时检测5-羟甲基-2-糠醛(5-hydroxymethyl-2-furfural,HMF)、甲基糠醛(5-methyl furfural,MF)和糠醛(furfural,FF)的方法;然后以葡聚糖为研究对象,重点分析不同程度酸水解条件对葡聚糖生成HMF、MF、FF的影响规律。结果显示:利用HLB固相萃取柱富集糠醛类化合物并结合超高效液相色谱测定3种糠醛类化合物含量的方法,具有快速、准确,灵敏度高的特点。进一步研究显示,未完全酸水解条件(0.5 mol/L H_(2)SO_(4),60℃)下,葡聚糖水解为单糖的回收率低,未测到3种糠醛类化合物。随着水解条件加剧,较优酸水解条件(2 mol/L H_(2)SO_(4),100℃)下葡聚糖水解为单糖的含量增加,同时HMF生成速率和含量显著增加,并检测出一定量的FF,但生成速率和含量低于HMF。过度酸水解条件下(4 mol/L H_(2)SO_(4),120℃),单糖回收率低于较优酸水解,HMF、FF含量较高,但在整个研究过程中未检测到MF。上述结果表明,葡聚糖水解过程中,糠醛类化合物产量与水解液中的单糖含量有密切关系;此外,加剧酸水解条件会促进葡聚糖水解产物中HMF、FF生成,其中HMF最易生成,其次为FF,MF生成还需更剧烈的条件进行催化。

In this study,a method for the simultaneous detection of 5-hydroxymethyl-2-furfural(HMF),5-methyl furfural(MF)and furfural(FF)was established by ultra-high performance liquid chromatography(UPLC)after enrichment of furfurals in the acid hydrolysate of dextran by solid phase extraction(SPE)using a hydrophilic-lipophilic balance(HLB)column.The effect of different degrees of acid hydrolysis of dextran on the production of HMF,MF and FF was analyzed.The results showed that the proposed UPLC method was rapid,accurate and sensitive.Under incomplete acid hydrolysis conditions(0.5 mol/L H_(2)SO_(4),60℃),the recovery of monosaccharides from dextran was low and the three furfural compounds were undetectable in the hydrolysate.Under the optimal hydrolysis conditions(2 mol/L H_(2)SO_(4),100℃),the content of monosaccharides in dextran hydrolysate increased,the formation rate and content of HMF increased significantly,and FF was detected;however,the formation rate and content of FF were lower than those of HMF.Under excessive hydrolysis conditions(4 mol/L H_(2)SO_(4),120℃),the recovery of monosaccharides was lower than that under the optimal hydrolysis conditions.Meanwhile,the contents of HMF and FF were higher,and MF was not detected during the whole hydrolysis process.The above results show that during the hydrolysis of dextran,the yield of furfural compounds is closely related to the monosaccharide content in the hydrolysate.In addition,more vigorous acid hydrolysis conditions will promote the formation of HMF and FF in dextran hydrolysate,HMF being the easiest to form,followed by FF.The formation of MF requires more vigorous catalytic conditions.