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Effects of buffer properties on cyclodextrin glucanotransferase reactions and cyclodextrin production from raw sago (cycas revoluta) starch

机译:缓冲液性能对西米生淀粉的环糊精葡糖基转移酶反应和环糊精生产的影响

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摘要

Results from the present study have shown that the ionic species of buffers, pH values and reaction temperature can affect the enzyme unit activities and product specificity of Toruzyme® (Novo Nordisk A/S Bagsvaerd, Denmark) CGTase (cyclodextrin glucanotransferase). Applying a similar reaction environment (acetate buffer, pH 6.0; temperature, 60 °C), the CGTase was found to be capable of producing pre dominantly β-cyclodextrin from either raw or gelatinized sago (Cycas revoluta) starch. Changing the buffer from acetate to phosphate reduced the yield of β-cyclodextrin from 2.48 to 1.42 mg/ml and also affected the product specificity, where production of both α- and β-cyclodextrins were more pronounced. The decrease in the production of cyclodextrins in phosphate buffer was significant at both pH 6.0 and 7.0. However, changing the buffer to Tris/HCl (pH 7.0) showed a significant increase in β-cyclodextrin production. Increasing the ionic strength of sodium acetate and Tris/HCl buffers at pH 6.0 and 7.0 to equivalent ionic strength of phosphate buffers showed no significant effects on cyclodextrin production. Higher yield of cyclodextrins at pH 7.0 when Tris/ HCI was used might be due to the binding of chloride ions at the calcium-binding sites of the CGTase, resulting in the shift of the optimum pH close to physiological environment, leading to an increase in the activities and specificity.
机译:从本研究的结果表明,缓冲液的离子种类,pH值和反应温度会影响Toruzyme®(Novo Nordisk A / S Bagsvaerd,丹麦)CGTase(环糊精葡聚糖转移酶)的酶单位活性和产物特异性。应用类似的反应环境(醋酸缓冲液,pH 6.0;温度,60°C),CGTase被发现能够从原料或糊状的西米(苏铁)淀粉生产占主导地位的β-环糊精。将缓冲液从醋酸盐更改为磷酸盐,将β-环糊精的产量从2.48降低至1.42 mg / ml,并且还影响了产品的特异性,其中α-和β-环糊精的生产更为明显。在pH 6.0和7.0下,磷酸盐缓冲液中环糊精的产量均显着下降。但是,更改为Tris / HCl(pH 7.0)的缓冲区显示出β-环糊精生产的显着增加。将乙酸钠和Tris / HCl缓冲液在pH 6.0和7.0下的离子强度提高到磷酸盐缓冲液的等效离子强度,对环糊精的生产没有显着影响。当使用Tris / HCl时,pH 7.0时环糊精的收率较高,这可能是由于氯离子在CGTase的钙结合位点上的结合,导致最佳pH值移向生理环境,从而导致pH值增加。活动和特异性。

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