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首页> 外文期刊>Biotechnology Progress >Effects of Substrate Pretreatment and Water Activity on Lipase-Catalyzed Cellulose Acetylation in Organic Media
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Effects of Substrate Pretreatment and Water Activity on Lipase-Catalyzed Cellulose Acetylation in Organic Media

机译：底物预处理和水分活度对有机介质中脂肪酶催化纤维素乙酰化的影响

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摘要

Lipase-catalyzed acetylation of cellulose solubilized in the dimethyl sulfoxide/paraform-aldehyde organic solvent system was conducted with lipase A12 from Aspergillus niger.The accompanying side cellulase activity of the A.niger lipase partly accounted for the enhanced acetylation mediated by the enzyme,via facilitating the partial degradation of cellulose substrate as evidenced by high-performance size exclusion chromatograph analysis.The enzymatic cellulose acetylation was improved by substrate pretreatment with cellulase or ultrasound by 18 and 14%,respectively,as a result of the reduced substrate molecular size.Additionally,the ultrasound-pretreated cellulose as the starting substrate was beneficial for the cellulose solution preparation due to the increased accessible surface of cellulose as evidenced by its increased sedimentation volume and SEM micrographs.The effect of thermodynamic water activity (a_w)on lipase catalytic activity in organic media was also investigated.The maximum acetylation extent (nearly 11 wt %)occurred at a_w =0.52,which was improved by 51% relative to the enzymatic reaction with no control of water activity.The much larger extent to which the lipase-catalyzed cellulose acetylation was enhanced by water activity optimization than by substrate pretreatment further supported the predominant role played by the major lipase activity of the A.niger lipase over its side cellulase activity in catalyzing cellulose ester synthesis in organic media.
机译：用来自黑曲霉的脂肪酶A12进行脂肪酶催化溶解在二甲基亚砜/多聚甲醛-有机溶剂体系中的纤维素的乙酰化反应。高效尺寸排阻色谱分析表明，这有助于促进纤维素底物的部分降解。由于底物分子大小的减少，用纤维素酶或超声波对底物进行预处理可使酶促纤维素乙酰化分别提高18％和14％。超声波处理的纤维素作为起始基质对纤维素溶液的制备是有益的，这是因为其增加的沉降体积和SEM显微照片证明了纤维素的可及性增加。热力学水活度（a_w）对脂肪酶催化活性的影响还对有机媒体进行了调查。在a_w = 0.52时发生的最大乙酰化程度（接近11 wt％），相对于不控制水活度的酶促反应提高了51％。脂肪酶催化的纤维素乙酰化程度大大提高了水活度比底物预处理的优化还进一步支持了黑曲霉脂肪酶的主要脂肪酶活性超过其侧纤维素酶活性的主要作用，以催化有机介质中纤维素酯的合成。

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