凝乳酶添加量对牦牛乳硬质干酪蛋白质降解的影响

通过测定不同可溶性氮含量以及采用尿素凝胶电泳法,研究了不同小牛皱胃酶添加量对牦牛乳硬质干酪3个月成熟过程中蛋白质降解的影响,并对干酪苦味进行了感官评价。研究表明:凝乳酶添加量对干酪p H 4.6SN和12%TCASN影响显著(P0.05),在成熟1个月时,不同凝乳酶添加量干酪p H 4.6SN之间差距较大,且凝乳酶添加量与干酪p H 4.6SN间存在较强线性关系。凝乳酶添加量对5%PTASN和游离氨基酸影响不显著(P0.05)。尿素凝胶电泳显示:干酪中αs-酪蛋白降解依赖于凝乳酶添加量,且降解程度大于β-酪蛋白。凝乳酶添加量对干酪苦味影响显著(P0.05),且随着凝乳酶添加量的增多,其苦味程度逐渐加重,但是大部分干酪苦味属于轻微苦味和中等程度苦味之间。干酪苦味与12%TCASN、αs-酪蛋白和β-酪蛋白降解率之间具有较强相关性(Spearman相关系数0.7,P0.01)。     

UV/Fe3+/H2O2体系降解活性艳橙X-GN废水

在自制的光催化反应器中,采用UV/Fe3+/H2O2体系光解活性艳橙X-GN模拟废水,考察了X-GN、Fe3+和H2O2初始浓度、初始pH值及温度对光解过程的影响.结果表明,在8 W低压汞灯(λ＝254 nm)照射下,UV/Fe3+/H2O2能够有效地降解结构稳定的X-GN.在pH值3.0,温度为50 ℃,时间为120 min,Fe3+和H2O2初始浓度分别为2.5×10-5 mol/L和1.5×10-4 mol/L时,含200 mg/L X-GN模拟废水的色度去除率和矿化率分别达到100 %和90.15 %.依据离子色谱 (IC)和GC/MS对X-GN降解中间产物和最终产物的鉴定,证实了X-GN氧化和TOC降解不同步的中间产物存在.     

降解木片树脂的白腐菌菌种选育与脱除树脂过程

通过在自然界采集、室内平板初筛及平板变色反应复筛得到了20株白腐菌菌株，并对变色系数最小的一株菌株G进行松木片固体接种实验。测定经2种不同浓度无机盐稀释的菌悬液接种松木片3天、5天、7天、9天后的木紊、树脂降解情况。结果显示，随着接种时间增加，松木片失重率逐渐增大，Klason木素、酸溶木素和总木紊含量逐渐下降，苯-醇抽出物和二氯甲烷抽出物含景也逐渐减少。表面扫描电镜照片表明，接种白腐菌的木片细胞壁上产生了明显的腐朽沟槽等现象；白腐菌菌丝在木片表面的生长呈由少到多、由凌乱到较有规律排列；松木片切片断面显微结构显示菌丝在细胞壁部位及胞间层也开始出现，这说明菌丝开始向细胞内部渗透。     

油烟废气中脂肪酸降解菌的选育和降解条件

从受油烟废气污染严重的土壤中分离、筛选出一株具有较强的降解油酸能力的ZFS-1菌株。最佳生长条件为：碳源2．33g／dL、氮源0．53g／dL、摇床转速180r／min。最佳的降解条件：温度33℃，pH7.5，接种体积分数为10％，油酸质量浓度0．79mg／mL，18h后油酸的降解率达到85%以上。     

Fate of the glucose degradation products 3-deoxyglucosone and glyoxal during peritoneal dialysis

Conventional fluids for peritoneal dialysis (PD) contain reactive glucose degradation products (GDPs) as a result of glucose breakdown during heat-sterilization. GDPs in PD fluids (PDFs) have been associated with the progressive alteration of the peritoneal membrane during long-term PD by cytotoxic effects and formation of advanced glycation endproducts (AGEs). In this study, we investigated the possible fate of two characteristic GDPs, 3-deoxyglucosone (3-DG) and glyoxal, during PD. In vivo, 3-DG and glyoxal concentrations, which were analyzed by high-performance liquid chromatography (HPLC), decreased in PDFs by 78% and 88% during 4 h of dwell time. The PDFs were then incubated in vitro in the presence of the most important reaction partners of GDPs in the peritoneal cavity. Neither human peritoneal mesothelial cells, human peritoneal fibroblasts, soluble protein, an insoluble collagen surface, nor components of spent dialysate led to a significant reduction of 3-DG or glyoxal after 6 h. Only after long-term incubation, a noticeable decrease of 3-DG was observed (-37% after three weeks), more likely due to spontaneous degradation reaction than formation of advanced glycation endproducts. These results suggest that in the course of PD, 3-DG, and glyoxal are absorbed into the organism and thus might contribute to the systemic pool of reactive carbonyl compounds.     

Microbial degradation of rice and barley straws in the sheep rumen and the donkey caecum

The chemical composition, intake, digestibility, ultrastructure and microbial degradation of rice straw from Camargue were compared with barley straw. These variables were observed in two different herbivore digestive ecosystems: the sheep rumen and the donkey caecum. The two straws differed essentially in their ash content, which was three times higher in rice, owing to its silica content. Other chemical components were comparable, except a higher phenolic acids‐to‐lignin ratio in rice. Rice straw was better ingested than barley straw. Organic matter and neutral detergent fibre digestibilities were the same in both straws. Dry matter and cell wall disappearances could be adjusted to the exponential modelling equation with lag time, and differed between animals but not between straws. The sheep rumen had a higher extent of degradation, but the donkey caecum had a higher degradation rate. Statistical analysis revealed that cell‐wall components degradation was similar in the two straws except for ferulic acid, which was more degraded in rice straw. Scanning electron microscopy showed important differences in parenchyma degradation, which was much more effective in rice. Copyright © 2003 Society of Chemical Industry     

Study of albedo and carpelar membrane degradation for further application in enzymatic peeling of citrus fruits

The enzymatic activity of four commercial enzymatic preparations (Peelzym I, II, III and IV) on citrus pectin, polygalacturonic acid and carboxymethylcellulose was determined (measured as the decrease in relative viscosity). In addition, the effectiveness of these preparations in the enzymatic degradation of the albedo and the segment membrane from Cimboa fruits was assessed. The highest activity on citrus pectin was shown by Peelzym II, although Peelzym I and IV activities were also elevated, 94.5 ± 6.2% and 88.7 ± 8.3% respectively of Peelzym II activity, and no relevant differences were found between them. Peelzym II also showed the highest activity for polygalacturonic acid, which was approximately 25% more than that of Peelzym I and IV, and more than double that of Peelzym III. Peelzym IV showed 40% more EM‐cellulase activity than Peelzym I, II and III. Segment membrane solution was degraded mainly by the enzymatic preparations Peelzym I and II. Thus, the most effective activities for the degradation of the carpelar membrane from Cimboa were those activities which act mainly on pectin and especially on polygalacturonic acid. However, the albedo was degraded to the greatest extent by Peelzym II and, in turn, the most important activities for albedo degradation were those which act on polygalacturonic acid. In addition, the concentration of the enzymatic preparation for the degradation of the carpelar membrane was lower than that required for albedo degradation. Copyright © 2004 Society of Chemical Industry     

Numerical analysis of the electrochemical dissolution of iridium catalyst and evaluation of its effect on the performance of polymer electrolyte membrane water electrolyzers

A physicochemical model of a water electrolyzer with a polymer electrolyte membrane (PEM) was developed, taking into account the electrochemical dissolution of an anodic iridium catalyst. The dependencies of the rates of iridium loss and electrolysis voltage increase upon the current density were calculated in order to analyze the effect of the iridium dissolution on degradation of the electrolysis cell (EC) performance. As an estimated characteristic of the techno-economic costs of the electrolysis process, the amount of iridium loss from the anode catalyst layer (as a result of electrochemical dissolution) in the course of the generation of 1 kg of hydrogen was calculated. Data were analyzed and a number of regularities of the iridium dissolution and its influence on the rate of degradation of the EC performance were found. In particular, the most efficient ECs in terms of electrolysis voltage (energy consumption for gas production) are, simultaneously, the most unstable (prone to performance degradation) in relation to the iridium dissolution process. An aim of current requirements for water electrolyzers includes reducing the specific consumption of iridium required for hydrogen generation.     

Tuning the surface hydrophilicity of a C3N4 nanosheet for efficient photocatalytic H2 evolution coupled with microplastic degradation

Simultaneously realizing highly-efficient degradation of microplastics coupled with H₂ evolution is urgently demanded to solve the white pollution and energy shortage issues. Herein, we fabricate a series of fragmented hydrophilic homogeneous carbon nitride (TP-PCN) by terminating the polymerization of carbon nitride using iodide ions (I⁻), which acts as an invisible inhibitor by breaking the π-π bond to reduce the accumulation of ultra-thin layers in PCN to inhibit the polymerization. The H₂ evolution rate of resultant photocatalyst could reach 600.3 μmol g⁻¹ h⁻¹ in alkaline polyethylene terephthalate (PET) solution, exhibiting outstanding photocatalytic activity. Meanwhile, the PET was also degraded into small molecules, which were used in agricultural production, food processing and pharmaceuticals. The high photocatalytic activity of the TP-PCN photocatalyst can be ascribed to the promoted hydrophilicity and charge separation ability. This work supplies new insights for the design of functional photocatalysts and developing green technologies to solve environment pollution.     

不同衰退机理对PEMFC怠速工况性能衰退影响的模拟研究

分析质子交换膜燃料电池(PEMFC)怠速工况衰退机理,确定怠速工况不同衰退机理对燃料电池模型参数的影响,采用所建立的PEMFC二维等温多物理场模型,仿真研究燃料电池在怠速工况衰退前后的性能及各种衰退因素对电压衰减量的贡献和内部反应气体分布变化。研究结果表明,阴极活化损失增大是怠速工况下最重要的衰退因素,其次是开路电压衰退,影响最小的是阴极电化学活性面积衰退;在相同操作条件下,衰退后燃料电池的最低氧气摩尔浓度和最低氢气摩尔浓度上升,电流密度分布不均匀现象加剧。