Rice bran polysaccharides (RBPSs) are the major active constituents of rice bran (RB). In this study, we utilized intracellular enzymes from Grifola frondosa to modify RBPSs, which were extracted from RB using ultrasound. To enhance the effect on natural killer (NK) cell cytotoxicity of modified polysaccharides (mRBPSs) generated from RBPSs, an orthogonal test (L9 [3]4 ) was employed to optimize the modification conditions. Based on the results of a single-factor test, the enzyme to polysaccharide ratio, reaction temperature, reaction pH, and reaction time were the main factors affecting mRBPSs-enhanced NK-cell cytotoxicity. The best conditions were determined to be an enzyme to polysaccharide ratio of 1:5, a reaction temperature of 40 °C, a reaction pH of 4, and a reaction time of 4 hr. By optimizing the conditions, the NK-cell cytotoxicity induced by mRBPSs6 was the highest, increasing by 12.01% ± 0.08%. Gas chromatographic analysis revealed that mRBPSs6 consists of rhamnose, arabinose, xylose, mannose, glucose, and galactose at a molar ratio of 7:21:6:5:53:48, which was 8:13:8:5:44:44 before modification. High-performance liquid chromatography results indicated molecular weights for the RBPSs of approximately 106 Da, which decreased to 104 to 105 Da after modification. Antioxidant activity tests revealed high capacity of mRBPSs6 for scavenging 1,1-diphenyl-2-picrylhydrazyl radicals and hydroxyl free radicals at 1.0 mg/mL. PRACTICAL APPLICATION Rice bran polysaccharides (RBPSs) contain compounds with many biological activities. However, these polysaccharides difficult to absorb due to high molecular weights and unexposed active sites, which are the main factors that limit their use in functional foods. The results of this study demonstrate that modification of RBPSs using intracellular enzymes from an edible fungus alters the molecular weights and monosaccharide composition of RBPSs. In addition, immune and antioxidant activities of RBPSs were increased. The findings provide a new and beneficial application for rice bran.

中文翻译：

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灰树花酶对米糠多糖的酶促修饰：自然杀伤细胞的细胞毒性和抗氧化活性

米糠多糖（RBPSs）是米糠（RB）的主要活性成分。在这项研究中，我们利用来自灰树花的细胞内酶来修饰 RBPS，它们是使用超声波从 RB 中提取的。为了增强由 RBPS 产生的修饰多糖 (mRBPS) 对自然杀伤 (NK) 细胞细胞毒性的影响，采用正交试验 (L9 [3]4 ) 来优化修饰条件。根据单因素试验的结果，酶多糖比、反应温度、反应pH和反应时间是影响mRBPSs增强NK细胞细胞毒性的主要因素。最佳条件被确定为酶与多糖的比例为 1:5，反应温度为 40 °C，反应 pH 为 4，反应时间为 4 小时。通过优化条件，mRBPSs6诱导的NK细胞细胞毒性最高，增加了12.01%±0.08%。气相色谱分析显示mRBPSs6由鼠李糖、阿拉伯糖、木糖、甘露糖、葡萄糖和半乳糖组成，摩尔比为7:21:6:5:53:48，即8:13:8:5:44:44修改前。高效液相色谱结果表明 RBPS 的分子量约为 106 Da，改性后降至 104 至 105 Da。抗氧化活性测试表明，mRBPSs6 在 1.0 mg/mL 时具有高清除 1,1-diphenyl-2-picrylhydrazyl 自由基和羟基自由基的能力。实际应用 米糠多糖 (RBPSs) 含有具有多种生物活性的化合物。然而，这些多糖由于分子量大和未暴露的活性位点而难以吸收，这是限制它们在功能性食品中使用的主要因素。这项研究的结果表明，使用来自食用菌的细胞内酶修饰 RBPS 会改变 RBPS 的分子量和单糖组成。此外，RBPSs的免疫和抗氧化活性增加。该发现为米糠提供了一种新的有益应用。