Isolation and Characterization of Pectin Methylesterase from Apple Fruit

Two forms of the enzyme pectin methylesterase are evidenced in the apple (Malus communis). They differ both in their charge and molecular weight. The two enzymes were separated by DEAE-cellulose chromatography. Their molecular weights, determined by gel-filtration, were 55000 and 28000 daltons. The heavier form has been purified at homogeneity and subjected to investigations regarding its activity as a function of the pH and temperature, and determination of its kinetic parameters. The enzyme has a Km value of 1.05 mg/mL for citrus pectin and an optimum activity in the pH range between 6.5-7.5. The enzyme was stable up to 40°C. Incubation for 1 min at 90°C leads to its complete inactivation.     

红枣果酒的研制

以红枣为原料,经榨汁并调整糖度后,采用优良酿酒酵母进行发酵,酿制出红枣果酒.     

沙棘果原花青素的分离纯化研究

用大孔树脂、Sephadex LH-20凝胶色谱的方法和反相高效液相色谱分离纯化沙棘果中的原花青素。结果表明：大孔树脂层析法分离纯化沙棘果中的原花青素时使用50％的乙醇水溶液洗脱得到的洗脱液中原花青素的含量较高，达71．9％；将经过大孔树脂层析分离纯化的原花青素粗品经Sephadex LH-20柱分离，50％乙醇作为流动相，原花青素粗品可纯化至95％以上。反相高效液相色谱分析发现，从Sephadex LH-20洗脱下来的组分中含有原花青素的二聚体。     

Purification and Characterization of an Endoprotease from Melon Fruit

An endoprotease was purified from melon fruit (Cucumis melo L.) by ammonium sulfate precipitation, gel filtration and ion-exchange chromatography using t-butyloxycarbonyl-Ala-Ala-Pro-Leu p-nitroanilide as a substrate. The molecular weight was estimated as 26,000 and isoelectric point pH 9.5. It preferentially hydrolyzed peptide bonds of the carboxyl terminal sides of Leu, Ala, His, Gin, and Am. Activity was strongly inhibited by diisopropyl phosphofluoridate, indicating the serine protease nature of the enzyme. The migration distance on electrophoresis, molecular weight and substrate specificity differed from cucumisin, a known protease from melon. This unusual protease may have potential for special food treatment applications.     

Isolation of Nanocellulose from Pomelo Fruit Fibers by Chemical Treatments

This study aims to isolate cellulose nanofibers from locally abundant pomelo fruit. The peels were subjected to alkali treatment (NaOH) with different concentrations and soaking times. Acid hydrolysis was also carried out to obtain an aqueous suspension of nanocellulose. The treated cellulose fibers were characterized by various methods. Alkali treatment was able to remove noncellulosic constituents. Microscopy techniques yielded morphology of elementary fibers with a compact structure with both micro- and nano-scaled fibers. An improved onset of degradation was likely caused by an increase in crystallinity evidenced by X-ray diffractometry (XRD). Acid hydrolysis could successfully individualize cellulose nanofibers as observed by transmission electron microscopy (TEM).     

黄瓜过氧化物酶的分离纯化及酶学性质

新鲜的黄瓜经匀浆、抽提、硫酸铵沉淀、CM-Sepharose 离子交换层析、Superdex-200凝胶过滤层析后获得电泳纯的过氧化物酶。该酶的比活力、回收率及纯化倍数分别为64 177.67 U/mg、9.58%、61.93。该酶的分子质量为41.15 kD,亚基分子质量为40.21 kD。该酶的最适温度和最适pH值分别为60 ℃和6。在25～45 ℃及pH 5～9的范围内非常的稳定。在测定条件下测得该酶的Km值为53.79 mmol/L。硫氰化钾对该酶活力基本无影响。尿素、K+、Mn2+、Ca2+、Mg2+、Ba2+、Cu2+对该酶都具有激活作用且浓度至50 mmol/L时酶活力分别被激活至112%、127%、113%、128%、139%、199%、348%,然而十二烷基磺酸钠、抗坏血酸和草酸对该酶有强烈的抑制作用;Zn2+、甲醇、乙醇和异丙醇对该酶有一定的抑制作用。     

猪皮Ⅰ型胶原蛋白的提取及其结构表征

采用酸膨胀-胃蛋白酶降解的新方法,从猪皮中提取Ⅰ型胶原蛋白。用原子力显微镜(AFM)观察了所提取的Ⅰ型胶原蛋白的形貌结构,用SDS-PAGE方法测得所提取的Ⅰ型胶原的相对分子质量为295kDa。结合紫外、红外检测和DSC分析,与市售SigmaⅠ型胶原对比,证实了提取物为Ⅰ型胶原蛋白,且很好的保持了Ⅰ型胶原的3股螺旋结构。     

Isolation and Characterization of Native Starch from Cocoa Beans

This paper describes the isolation and characterization of native starch from fermented cocoa beans. The isolation procedure is based mainly on the mild extraction of compounds soluble in different extractants and flocculation of non-starch polymeric material at a pH of 2.7. The isolated, egg-shaped starch granules have a mean size of 4.4 μm, ranging from 1.5 to 8 μm, an amylose content of 30.4%, a gelatinization temperature from 52.5 to 68°C, and a limiting viscosity number of 166.2 ml/g in 1-N potassium hydroxide solution.     

酵母蔗糖酶的提取方法

采用甲苯自溶法、冻融法、SDS抽提法3种方法从酵母中提取蔗糖酶,经质量分数50%的乙醇分级沉淀、Mono Q阴离子交换柱层析纯化后,制得高纯度的酵母蔗糖酶。比较了上述3种提取方法并对该酶的部分性质进行了研究。纯化的酶经等电聚焦测定,等电点为5.6,SDS-PAGE鉴定其相对分子质量为60kD。以蔗糖为底物测得酵母蔗糖酶的表观米氏常数Km为0.013mol/L。结果显示3种提取方法各有优劣,冻融法和SDS抽提法的提取效率远高于传统的甲苯自溶法。其中SDS抽提法的效率最高,加之其操作简便,更适合于酵母蔗糖酶大规模的制备提取。     

枸杞子阿拉伯聚糖的提纯分离及其构造特征研究

对枸札子水溶性粗多糖进行了分离提纯和化学构造研究。除了已经报道过的4种糖蛋白AGP（Arabinogalactan-protein:Cp-1-C,Cp-1-D,Cp-2-B和Hp-2-C)外，还得到了一种均一的阿拉伯聚糖（Hp-0-A,分子量23，000），运用甲基化分析及其NMR技术确定了其主要构造特征。     

Effect of Pear,Apple and Date Fibres from Cooked Fruit By-products on Dough Performance and Bread Quality

This study examined the effect of the incorporation of flesh fibre concentrate (FFC) from apple, pear, and date pomaces on wheat bread dough performance and bread quality. The nutritional composition and techno-functional properties (water-holding capacity, oil-holding capacity, swelling capacity) of FFC were determined beforehand. Dough performance was evaluated by farinograph, alveograph and visco-amylograph. Bread quality was assessed by physical (weight, specific volume, and color) and textural (hardness and elasticity) parameters. Digital imaging analysis was also performed in order to better understand the observed effects. Results showed that the addition of FFC in wheat flour significantly improved (P?<?0.05) dough properties inducing an increase of water absorption (from 55 to 60 %), of stability (from 4 to 31 min),of tenacity (from 83 to 116 mmH₂O) , a reduction of extensibility (from 69 to 29 mm), of softening (from 60 to 20 BU), of breakdown (from 34 to 25 BU) and of setback (from 103 to 93 BU) in comparison to the control dough (without fibre). The formulation containing FFC produced loaves that had various colors (crust, 0?<?ΔE*?<?10 and crumb, 0?<?ΔE*?<?20; ΔE* corresponding to color variation), a comparable specific volume (2.7 vs 2.9 cm³/g for control) and a more aerated internal crumb structure compared to the control. During storage of breads at 20 °C, there was no significant difference (P?<?0.05) between enriched and control bread crumb and crust texture profiles.     

韭菜过氧化物酶的分离纯化及性质

经匀浆、抽提、硫酸铵分级沉淀、CM-Sepharose 离子交换层析、Superdex-200凝胶过滤层析,获得电泳纯的韭菜过氧化物酶(POD)。该酶比活力达到14031.41U/mg,纯化倍数为102.96,回收率为10.85%。该酶分子质量约为28.4kD,最适温度40℃、最适pH值为4.6。该酶在20～40℃以及pH 4.0～8.0有较好的稳定性,在最适条件下测得其Km值为18.15mmol/L。低浓度草酸、Zn2+、Mg2+等对该酶有较强激活作用;甲醇、乙醇、异丙醇、SDS、抗坏血酸(AsA)以及Mn2+、Fe3+等对该酶有较强的抑制作用。     

芦荟过氧化氢酶的分离纯化和性质研究

目的：获得库拉索芦荟过氧化氢酶纯品并对其性质进行研究。方法：采用硫酸铵分级沉淀,DEAESepharose阴离子交换层析,CM-Sepharose 阳离子交换层析和Sephacryl S-200 凝胶层析对酶蛋白进行分离纯化,采用SDS-PAGE 鉴定酶的纯度、分子质量。结果：从芦荟中分离纯化获得电泳纯的过氧化氢酶,纯化倍数为228.05倍,酶活力回收率为14.10%,比活力达17427.30U/mg。该酶的分子质量为239.90kD,亚基分子质量为60.60kD。推测该酶由4 个相同亚基构成。该酶最适温度为45℃,最适pH 值为7.5,以过氧化氢为底物测定该酶的表观Km 为34mmol/L。结论：成功分离纯化获得过氧化氢酶,该酶具有良好的热稳定性和酸碱耐受性。     

芫荽酸性磷酸酶的提取、纯化及酶学性质研究

采用硫酸铵分级沉淀、CM-Sepharose离子交换层析、Superdex-200凝胶过滤层析法,从新鲜芫荽中分离纯化出电泳纯的酸性磷酸酶（acid phosphatase,ACP）。该酶的酶活回收率为14.20%、纯化倍数为238.60、酶比活力为295.87 U/mg、亚基分子质量约为53.8 kD;芫荽ACP酶学性质研究结果表明：该酶的最适反应温度为55 ℃,在50 ℃以下时较稳定,因此该酶对温度较敏感;该酶的最适反应pH值为5.8,在pH?4.0～7.0之间较稳定,表明该酶耐受于酸性环境;芫荽ACP的对硝基苯酚磷酸二钠Km值为0.63 mmol/L,表明该酶与底物对硝基苯酚磷酸二钠具有较高的亲和力;甲醇、乙醇、异丙醇、抗坏血酸、草酸、Cu2＋、Pb2＋、Ag＋对该酶具有强烈的抑制作用;Mg2＋、Mn2＋、Ba2＋、K＋对该酶具有一定的激活作用。     

Isolation and Identification of Lactic Acid Bacteria from Fermented Red Dragon Fruit Juices

Abstract: Red dragon fruit or red pitaya is rich in potassium, fiber, and antioxidants. Its nutritional properties and unique flesh color have made it an attractive raw material of various types of food products and beverages including fermented beverages or enzyme drinks. In this study, phenotypic and genotypic methods were used to confirm the identity of lactic acid bacteria (LAB) appeared in fermented red dragon fruit (Hylocereus polyrhizus) beverages. A total of 21 isolates of LAB were isolated and characterized. They belonged to the genus of Enterococcus based on their biochemical characteristics. The isolates can be clustered into two groups by using the randomly amplified polymorphic DNA method. Nucleotide sequencing and restriction fragment length polymorphism of the 16S rRNA region suggested that they were either Enterococcus faecalis or Enterococcus durans. Practical Application: Current research revealed the use of biochemical analyses and molecular approaches to identify the microbial population particularly lactic acid bacteria from fermented red dragon fruit juices.     

鹰嘴豆多糖分离纯化和结构表征

以鹰嘴豆为原料,对其全豆、子叶、种皮等不同部位多糖分布和理化性质进行分析、比较,并研究鹰嘴豆种皮多糖(Cicer arietinum hull polysaccharide,CAHP)结构特征。根据得率和化学组成等结果,可推测鹰嘴豆多糖集中分布于其种皮部位;进一步采用柱层析分离法对CAHP纯化获得6个组分,并对其中得率较高且具有良好均一性的多糖组分CAHP-F_0.2进行结构表征。结果表明,CAHP-F_0.2以HG型果胶多糖为主,其主链由1,4-Galp A连接而成,并含有少量的RG-I型果胶结构域,同时存在阿拉伯聚糖侧链和阿拉伯半乳聚糖-II侧链。本研究将为鹰嘴豆多糖结构、生物活性研究和资源开发提供一定理论依据。     

Isolation and Characterization of Hemicellulose and Cellulose from Sugar Beet Pulp

Various conditions for the extraction of hemicellulose and cellulose from sugar beet pulp were examined, including pulp particle size, temperature of EDTA extraction, temperature and concentration of alkaline extraction, and delignification time. A procedure using 60 mesh pulp, 85°C EDTA extraction of pectins, 10% NaOH extraction at 25°C followed by one hour delignification gave the highest yields. Molecular weights of hemicellulose ranged from 40,000 to 150,000 daltons for the A form and 10,000 to 150,000 daltons for the B form. The monosaccharide composition of hemicellulose A and B differed significantly. Hemicellulose B had the highest water-holding capacity followed by hemicellulose A and cellulose. Viscosity of the hemicelluloses was very low.