双酶法提取芋头淀粉的工艺及性质研究

以芋头为原料,研究了木聚糖酶和中性蛋白酶的处理条件对淀粉回收率的影响,并通过正交优化确定了木聚糖酶的酶处理时间2 h,酶处理温度50℃,酶处理pH值5.0,酶添加量750 u·g-1;中性蛋白酶的酶处理时间3 h,酶处理温度50℃,酶处理pH值7.0,酶添加量500 u·g-1的工艺参数。比较不同加酶方式,表明先添加木聚糖酶后添加中性蛋白酶的二次加酶法所得淀粉回收率最高,可达78.77%。通过与马铃薯淀粉、木薯淀粉、红薯淀粉黏度特性的比较发现,芋头淀粉糊化温度高,热稳定性好,抗老化性强,但是凝胶性质较弱。     

酸性蛋白酶在酒精生产中的应用

酒精是一种引人瞩目的能源,其生产规模也日益壮大。降低成本,提高产率已成为企业所追求的目标,生产过程的酶制剂应用的深度探索也就成为了技术工作者所探究的重点。将酸性蛋白酶在酒精生产的应用、原理和实践数据提供给读者以作为参考和分析。     

碱性蛋白酶Alcalase酶解大米蛋白制备小分子肽的动力学研究

以大米蛋白为原料,用碱性蛋白酶Alcalase2.4 L酶解大米蛋白制备小分子多肽。采用单因素试验方法优化酶解条件,考察酶解过程中pH、加酶量、底物浓度和温度酶解初速度的影响,并建立了酶解动力学方程。研究了最优酶解条件下酶解过程中酶解产物的分子量分布状态。结果表明,Alcalase2.4 L酶解大米蛋白的最优pH 8.5、温度65℃、酶底比0.096 AU/g(底物),在酶解过程中存在产物抑制,在研究的底物浓度范围内(90 g/kg)不存在底物抑制。主要动力学参数为:Km为5.76(g·min)/mmol,Vmax为0.67mmol/(kg·min),k2为0.28 mmol/(AU·min)。酶解动力学方程为:1/V0=56.29/[S0][E0]+1/0.28[E0]。酶解至3 h时水解度达到16%,酶解产物的分子量在264~584 u之间的组分达到94%,酶解3 h后酶解产物的分子量分布基本保持不变。本研究结果为制备大米蛋白小分子活性肽奠定基础。     

Assessment of the production of Bacillus cereus protease and its effect on the quality of ultra-high temperature-sterilized whole milk

Bacillus cereus is one of the most important spoilage microorganisms in milk. The heat-resistant protease produced is the main factor that causes rotten, bitter off-flavors and age gelation during the shelf-life of milk. In this study, 55 strains of B. cereus were evaluated, of which 25 strains with protease production ability were used to investigate proteolytic activity and protease heat resistance. The results showed that B. cereus C58 had strong protease activity, and its protease also had the highest thermal stability after heat treatment of 70°C (30 min) and 100°C (10 min). The protease was identified as protease HhoA, with a molecular mass of 43.907 kDa. The protease activity of B. cereus C58 in UHT-sterilized whole milk (UHT milk) showed an increase with the growth of bacteria, especially during the logarithmic growth phase. In addition, the UHT milk incubated with protease from B. cereus C58 at 28°C (24 h) and 10°C (6 d) were used to evaluate the effects of protease on the quality of UHT milk, including protein hydrolysis and physical stability. The results showed that the hydrolysis of casein was κ-CN, β-CN, and α_S-CN successively, whereas whey protein was not hydrolyzed. The degree of protein hydrolysis, viscosity, and particle size of the UHT milk increased. The changes in protein and fat contents indicated that fat globules floated at 28°C and settled at 10°C, respectively. Meanwhile, confocal laser scanning microscopy images revealed that the protease caused the stability of UHT milk to decrease, thus forming age gelation.     

LiCl-ARTP复合诱变选育高产碱性蛋白酶菌株及其发酵条件优化

以地衣芽孢杆菌（Baclicus lincheniformis）E-417为出发菌株,采用氯化锂（LiCl）-常压室温等离子体（ARTP）复合诱变法对其进行诱变,通过酪蛋白平板初筛、摇瓶复筛、遗传稳定性验证筛选高产碱性蛋白酶的优良菌株,并通过单因素及响应面试验对其发酵产酶条件进行优化。结果表明,在氯化锂添加量为1.5%、ARTP照射时间为45 s的最适复合诱变条件下筛选得到1株高产碱性蛋白酶的优良菌株F-3,酶活达到12 147 U/mL,且该菌株传代8次后仍具有良好的遗传稳定性,其最适发酵培养基成分为玉米粉41 g/L、豆饼粉40 g/L、碳酸钠2.1 g/L、磷酸氢二钠2.0 g/L;最适发酵条件为发酵温度37 ℃、初始pH值7.0、接种量8%。在此优化条件下,碱性蛋白酶酶活达到16 156 U/mL,较原始菌株提高75%。     

沙蚕不同蛋白酶酶解产物滋味特征及聚类分析研究

摘要：目的 研究沙蚕不同酶解产物中氨基酸和呈味核苷酸的含量、组成和呈味效果差异。方法 以酱油粉为对照,采用味道强度值、味精当量、主成分分析法、聚类分析法进行分析和综合评价。结果 沙蚕不同蛋白酶解产物中游离氨基酸含量在90.84±1.12~151.25±0.95 mg/g之间;风味蛋白酶酶解产物的游离氨基酸和呈味氨基酸含量最高;胰蛋白酶组的味精当量值远高于酱油粉组;各组氨基酸对滋味有较大贡献,风味、胰蛋白酶组中谷氨酸的味道强度值值与酱油粉组中该值接近,分别为37.13和35.40 mg/g。提取了4个主成分,累计方差贡献率达95.372%,较好地反应了酶解产物中游离氨基酸的综合信息,风味蛋白酶组综合得分最高,基于电子舌的滋味轮廓也支撑了这一结论。采用聚类分析将实验组分为4类,较直观地反映了不同酶解产物间的差异。结论 风味蛋白酶和胰蛋白酶酶解沙蚕的产物游离氨基酸品质较好,且鲜味氨基酸含量和呈味核苷酸含量较高,可开发呈味基料。     

A preliminary study of the protease activities in germinating brown rice (Oryza sativa L.)

BACKGROUND: Proteases hydrolyse storage proteins to provide precursors for perpetuating species. The aim of this study was to investigate and characterise different proteases in germinating brown rice. RESULTS: The protease activity of brown rice increased sevenfold during 7 days of germination. It was highest on day 6 when determined at pH 3.5. With casein as substrate the proteases showed two catalytic groups: acidic proteases with an optimal pH of 3.5 and alkaline proteases with an optimal pH of 8.0. The acidic protease activity was inhibited by Ba²⁺ and Pb²⁺ but stimulated by Zn²⁺, while the alkaline protease activity was inhibited by Ca²⁺ and Pb²⁺ but stimulated by Mg²⁺ and Zn²⁺. SDS‐gelatin‐PAGE assay showed two protease activity bands at pH 3.5, while two different bands with higher molecular weights were observed at pH 8.0. Inhibition assay revealed that pepstatin A and E‐64 inhibited 67.63 and 38.26% respectively of the protease activity at pH 3.5, indicating the presence of aspartic and cysteine proteases. Metalloproteases played a major role under alkaline conditions (88.37% inhibition with EDTA). CONCLUSION: Germinated brown rice proteases fall into different classes with different properties. This study is helpful for their further purification. Copyright © 2010 Society of Chemical Industry     

2种蛋白酶水解牦牛血液蛋白工艺优化

目的 以牦牛血为原料，在碱性蛋白酶水解基础上，加入风味蛋白酶建立复酶分步水解牦牛血液蛋白工艺。方法 以蛋白水解率为指标，运用单因素与正交试验获得碱性蛋白酶水解工艺，在此基础上采用四因素三水平正交试验优化复酶水解pH、水解温度、酶浓度、水解时间，获得碱性蛋白酶与风味蛋白酶分步水解工艺。结果 复酶工艺为在底物浓度1:6 g/mL、最适pH9、最适温度55 ℃、1.00 %的碱性蛋白酶水解1 h后，调节pH到7，添加0.75 %的风味蛋白酶继续水解5 h，可获得最高蛋白水解率为30.77±0.18 %。结论 对研究酶水解牦牛血制备高附加值产品具有重要参考作用。     

COVID-19: Direct and Indirect Mechanisms of Statins

The virus responsible for the current COVID-19 pandemic is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): a new virus with high infectivity and moderate mortality. The major clinical manifestation of COVID-19 is interstitial pneumonia, which may progress to acute respiratory distress syndrome (ARDS). However, the disease causes a potent systemic hyperin-flammatory response, i.e., a cytokine storm or macrophage activation syndrome (MAS), which is associated with thrombotic complications. The complexity of the disease requires appropriate intensive treatment. One of promising treatment is statin administration, these being 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors that exert pleiotropic anti-inflammatory effects. Recent studies indicate that statin therapy is associated with decreased mortality in COVID-19, which may be caused by direct and indirect mechanisms. According to literature data, statins can limit SARS-CoV-2 cell entry and replication by inhibiting the main protease (Mpro) and RNA-dependent RNA polymerase (RdRp). The cytokine storm can be ameliorated by lowering serum IL-6 levels; this can be achieved by inhibiting Toll-like receptor 4 (TLR4) and modulating macrophage activity. Statins can also reduce the complications of COVID-19, such as thrombosis and pulmonary fibrosis, by reducing serum PAI-1 levels, attenuating TGF-β and VEGF in lung tissue, and improving endothelial function. Despite these benefits, statin therapy may have side effects that should be considered, such as elevated creatinine kinase (CK), liver enzyme and serum glucose levels, which are already elevated in severe COVID-19 infection. The present study analyzes the latest findings regarding the benefits and limitations of statin therapy in patients with COVID-19.     

高产蛋白酶菌株的分离、鉴定及酶学性质研究

该研究旨在从非传统环境（磷矿）中分离、筛选高产胞外蛋白酶菌株，对菌株进行形态学观察、生理生化和分子生物学鉴定，并研究其蛋白酶的酶学性质。结果表明，分离筛选到一株蛋白酶高产菌株，编号为PB5，该菌株被鉴定为贝莱斯芽孢杆菌（Bacillus velezensis），该菌株产胞外蛋白酶活力为562.3 U/mL，胞外蛋白酶的最适pH值为10，在pH 7～10有较好的pH稳定性；最适温度为60 ℃，20～50 ℃时有较好的稳定性；Na+、Mg2+、Mn2+、K+对蛋白酶活力有明显的促进作用；Fe2+、Ag+、乙二胺四乙酸（EDTA）、苯甲基磺酰氟（PMSF）、十二烷基硫酸钠（SDS）对蛋白酶活力有明显抑制效果。