生物降解淀粉颗粒的酶改性方法

为了提高淀粉颗粒对酶的敏感性，可以对颗粒进行适当的预处理以提高反应效率。目前常用的预处理方法有水热处理、超声波处理、冻融循环处理和机械处理等。水热处理作为一种物理预处理方式，包括湿热处理和退火处理，且这两种方式都会保留淀粉的颗粒形态。这两种方式都需要控制处理过程中淀粉的含水量、温度以及加热时间。

In order to improve the sensitivity of starch granules to enzymes, the granules can be pretreated appropriately to improve the reaction efficiency. At present, the commonly used pretreatment methods include hydrothermal treatment, ultrasonic treatment, freeze-thaw cycle treatment and mechanical treatment. As a kind of physical pretreatment, hydrothermal treatment includes moist heat treatment and annealing treatment, and both of them will retain the granular morphology of starch. Both methods need to control the water content, temperature and heating time of starch during the treatment.

酶法改性淀粉颗粒要保证在酶改性的过程中和改性后淀粉的颗粒形态始终得以保留。淀粉的糊化起始温度多在60 ℃左右，所以酶改性的温度一般不超过60 ℃。

The granule morphology of starch modified by enzyme should be kept during the process of enzyme modification and after modification. The initial gelatinization temperature of starch is usually about 60 ℃, so the temperature of enzymatic modification is generally not more than 60 ℃.

达到佳的改性时间后，添加酸或碱灭酶，在适当条件下离心后收集的淀粉经过蒸馏水或乙醇溶液洗涤、干燥，后研磨过筛制得酶法改性的淀粉颗粒。实验室研究酶法改性淀粉颗粒常用的干燥方法有真空干燥、冷冻干燥和烘箱干燥等。

After the optimal modification time is reached, acid or alkali is added to kill the enzyme, the starch collected after centrifugation under appropriate conditions is washed and dried with distilled water or ethanol solution, and then ground and sieved to obtain enzyme modified starch particles. Vacuum drying, freeze drying and oven drying are the common drying methods for enzymatic modified starch granules.

改性生物降解颗粒的形态结构通常采用扫描电子显微镜进行分析。扫描电子显微镜图中可以清晰地观察到颗粒表面的凹痕和孔洞，还可以根据不同酶解时间淀粉颗粒的电子显微镜图推测出酶对淀粉颗粒的作用方式和特点。

The morphology of modified biodegradable particles is usually analyzed by scanning electron microscope. The dents and holes on the surface of starch granules can be clearly observed in the scanning electron microscope. The action mode and characteristics of enzymes on starch granules can also be inferred from the electron microscope images of starch granules with different enzymatic hydrolysis time.

酶改性对淀粉颗粒的晶型和结晶度有不同程度的影响，这取决于酶和淀粉的种类以及改性时间。经过分支酶和转葡糖苷酶的组合修饰后，马铃薯淀粉的晶型由B型结晶转变为C型结晶。马铃薯淀粉颗粒晶型的转变可能是经酶修饰后，支链淀粉的B1链含量增加，颗粒非结晶区的分支密度增加，使分支点间距离的缩短，从而导致淀粉的自发重结晶。

Enzyme modification has different effects on the crystal form and crystallinity of starch granules, which depends on the type of enzyme and starch and the modification time. After modification with branching enzyme and transglucosidase, the crystalline form of potato starch changed from B-type to C-type. The transformation of potato starch granule crystal form may be that after enzyme modification, the B1 chain content of amylopectin increases, the branching density of the non crystalline region of the granule increases, and the distance between branching points shortens, resulting in the spontaneous recrystallization of starch.

由于对淀粉颗粒的改性在非糊化条件下进行，所以改性淀粉仍然保留了糊化特性，并且酶对淀粉颗粒的修饰会改变其糊化温度和糊化焓。分支酶修饰木薯淀粉颗粒引起改性淀粉糊化起始温度、糊化峰值温度和糊化焓升高。糊化起始温度的升高是由于淀粉颗粒的形态发生了变化，以及直链淀粉发生重结晶。糊化焓的提高表明改性使淀粉颗粒结构的稳定性提高。

Because the modification of starch granules was carried out under non gelatinization conditions, the gelatinization properties of modified starch were still retained, and the gelatinization temperature and enthalpy of starch granules were changed by enzyme modification. Modification of cassava starch granules by branching enzymes resulted in the increase of gelatinization initial temperature, gelatinization peak temperature and gelatinization enthalpy of modified starch. The increase of gelatinization initial temperature was due to the change of starch granule morphology and the recrystallization of amylose. The increase of gelatinization enthalpy showed that the stability of starch granule structure was improved by modification.

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