PURIFICATION AND PARTIAL CHARACTERIZATION OF A LECTIN FROM THE SEEDS OF DIOCLEA GUIANENSIS1

A lectin was purified from seeds of Dioclea guianensis by Sephadex G-50 affinity chromatography. Apparent homogeneity of the lectin was demonstrated by native polyacrylamide gel electrophoresis, chromatography on DEAE- and CM-Sepharose, and immunochemistry. The lectin showed a carbohydrate specificity for D-mannose (D-glucose)-binding, had a requirement for Ca^?2 and Mn^?2, contained no covalently bound carbohydrate and had an amino acid composition characterized by high content of aspartic acid, serine and threonine, and low levels of sulfur-containing amino acids. At pH 7.5 it exists as two species of molecular weight about 100 and 47 kD and in dissociating solvents three subunits of approximate size of 30, 18 and 12 kD were obtained. The lectin agglutinated erythocytes from rabbit and chicken but not from human, cow, sheep, goat or pig and was toxic to brine shrimp (Artemia salina) larvae. It was relatively heat-stable, retaining half of its original activity even after 90 min at 70°C.     

新型两性柔软剂的合成与性能

制备兼具阳离子和阴离子性能的柔软剂,硬脂酸,二乙醇胺 磷酸化剂,氢氧化钾以三步合成磷酸单－2－（2－硬脂酰氧基乙基）氨基乙酯钾盐,它是两性表面活性剂,具有去污,抗静电性好,柔软性优良,又不易使织物泛黄,对皮肤刺激性小的特点,很有发展前途。     

长白山大型食药用真菌凝集素的筛选

选取20种供试的长白山大型食药用真茵,通过Tris-HCl缓冲液浸提法,从这些真菌中粗提凝集素,以3%兔红细胞悬液对其凝血活性进行检测,以期筛选到凝集效价较高的真茵.结果表明,大部分长白山食药用真茵均具有凝血活性,且与其所属科属种无关.所有供试真菌中凝血效价最高的真菌为白桦茸和斑褐孔菌.     

GELATINIZATION BEHAVIOR OF GRAINS AND FLOUR IN RELATION TO PHYSICO-CHEMICAL PROPERTIES OF MILLED RICE (ORYZA SATIVA L.)

ABSTRACT

Physico‐chemical properties of milled rice grains of 13 japonica varieties were evaluated. The rice varieties differed in appearance. One sample had long grains (6.61 mm), two had short grains (5.27–5.32 mm) and the rest had grains of medium length (5.52–6.55 mm). The shape (length/width) of grains varied from bold (1.58–1.9) to medium (2.06–2.37). The protein content was high in all samples (7.82 to 9.72% on dry mass). Almost all, with exception of one cultivar (Osogovka), which had intermediate amylose content (23.3%), were low amylose varieties (12–19.4% amylose). Their minimum cooking time varied from 17.5 to 22.5 min. Significant correlations (P < 0.05) were established between some physico‐chemical characteristics of evaluated rice cultivars. Elongation during minimum cooking time was correlated with protein content (r = 0.6899), shape (?0.7137), thickness (0.7234) and width (0.9134) of grains. The rice flour paste viscosity correlated significantly with shape (0.6148) and length (0.7353) of grains. On the basis of the established results, it was concluded that appearance of milled rice could be used as indicator for predicting gelatinization behavior: elongation ratio (length after minimum cooking time/length of the grains) of the rice grains and viscosity of rice flour during cooking.

PRACTICAL APPLICATIONS

Results from this research constitute a useful tool to predict the gelatinization behavior of milled grains and flour of japonica rice varieties, on the basis of grain appearance. The appearance is critical in acceptability of rice varieties by the consumers. The possibility to predict rice grain behavior during cooking on the basis of its appearance could be an additional attribute or market value for consumer choice. The results could be used in selection of rice variety for rice grits or flour production and use in special applications.

     

PURIFICATION AND CHARACTERIZATION OF A PHYTASE FROM SPELT

Four soluble phytases were identified in germinating spelt. Although numerous purification strategies were applied, none of the four phytases could be purified to homogeneity. The purest phytase preparation, called D21, contained a phytase (major component) and an acid phosphatase (APH) (minor component). The phytase behaves like a monomeric protein of a molecular mass of about 68 kDa and shows a broad substrate specificity. Optimal pH for degradation of phytate was 6.0 and the optimal temperature 45C. Kinetic parameters for the hydrolysis of Na-phytate were K_M 400 μmoll^?1 and k_cat 368s^?1 at pH 6.0. The spelt phytase D21 degrades phytate stepwise.     

ISOLATION AND CHARACTERIZATION OF BACTERIOCIN-PRODUCING MICROORGANISMS FROM AGOS-OS

Agos-os, a fermented meat and sweetpotato mixture, was produced and analyzed for its microbial characteristics. pH decreased during fermentation. Mold and anaerobic bacterial counts increased while yeasts and aerobic bacterial counts decreased during the third and seventh day of fermentation. Six isolates with the widest zones of inhibition on the indicator lawn were selected for bacteriocin production. These isolates had exactly the same morphological, physiological and biochemical characteristics. The ribosomal RNA sequence was 99.5% identical with Enterococcus faecalis VRE 1492. The identification was confirmed through DNA homology test by the EMBL Genbank, Canada. This bacterium produced the L-isomer lactic acid. The amount of bacteriocin produced by the bacterium was optimized by growing the bacterium at different growth media, initial pH and fermentation time. Maximum production of bacteriocin was achieved in MRS (De Man Rugosa and Sharpe) medium (with glucose) at pH 7.50. The crude bacteriocin inhibited the growth of gram-positive bacteria such as Lactobacillus sake 15521 and Listeria innocua. The gram-negative bacteria such as Escherichia coli DH 5-alpha (with plasmid, PUC) , Salmonella typhii and Staphylococcus aureus were weakly inhibited. Other microorganisms such as Lactobacillus curvatus D31685 , Lactobacillus confusius M23036 , Lactococcus lactis MG1363 , Leuconostoc paramesenteroides S67831 , Pediococcus pentosaceus M58834 , Saccharomyces cerevisiae SS553 (wild type) and Escherichia coli JM109 (no plasmid) were not inhibited.     

ISOLATION AND CHARACTERIZATION OF MELANOIDINES FROM MALT AND MALT ROOTS

Preparative isolation of alcohol-soluble and water-soluble melanoidines from pale malt, caramel malt, coffee malt and malt roots was done. The distribution of melanoidines according to molecular weight and the spectral characterization of the separate fractions was studied by gel chromatography on Sephadex G-50. The melanoidines isolated from coffee malt have the largest molecular weights and those from pale malt the smallest. The alcohol-soluble melanoidines of malt are characterized by a greater diversity in spectra and absorbance maxima from 240 to 285 nm. The water-soluble melanoidines absorb in the region 265 to 283 nm.     

漆酶基因的克隆及在甲醇毕赤酵母中的表达

以白腐菌杂色云芝RNA为模板,通过RT—PCR获得不带自身信号肽漆酶Lccl基因的cDNA片段。构建了重组表达载体pMETαA—Lccl,并将其线性化后用电穿孔法导入Pichia methabolica PMAD16,PCR结果表明Lccl基因已经整合到甲醇毕赤酵母染色体上。经摇瓶培养筛选出表达水平较高的酵母菌株,漆酶酶活力达78U／L。     

PURIFICATION AND CHARACTERIZATION OF ENDOPROTEASES FROM FRUIT BODY OF 'SHIMEJI'MUSHROOM, Lyophyllum aggregatum

Two proteolytic enzymes, L.a. protease I and II, were purified from the fruit body of 'shimeji'mushroom, Lyophyllum aggregatum, by ammonium sulfate precipitation, gel filtration, hydrophobic chromatography and ion-exchange chromatography. The enzymes were assayed using t-butyloxycarbonyl-Ala-Ala-Pro-Phe p-nitroanilide as a substrate. Each of the final enzyme preparations was homogeneous on polyacrylamide gel electrophoresis. The molecular weights of the enzymes were estimated as 44,000 and 46,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzymes had the same optimal pH range of 7–8. Protease I preferentially hydrolyzed peptide bonds of the carboxyl-terminal sides of phenylalanine and leucine, and slowly hydrolyzed the peptide bonds of alanine, threonine and asparagine. On the other hand, protease II showed broader substrate specificity. Both enzymes were almost completely inactivated by diisopropyl phosphofluoridate, and partially inhibited by chymostatin. Protease I was also inhibited weakly by o-phenanthroline. These unusual proteases may have potential for specific food treatment applications.     

ISOLATION AND CHARACTERIZATION OF PECTINESTERASE FROM VALENCIA ORANGE1

Thermolabile (TL) and thermostable (TS) pectinesterases (PE) were extracted from the pulp of fresh Valencia oranges by enzyme hydrolysis using a native pH and high ionic strength buffer system. Each form was separated individually by CM-Sephadex C-50, Phenyl Sepharose CL-4B and CM-Bio-Gel A chromatography. TLPE and TSPE exist as multiple forms which were shown to differ in their stability and effects on cloud loss in single strength orange juice.     

CHARACTERIZATION OF WHEY PROTEINS FROM MONGOLIAN YAK, KHAINAK, AND BACTRIAN CAMEL

The composition of whey proteins from ruminant Mongolian domestic animals was analyzed and a comparative study between camel (Camelus bactrianus) and dromedary (Camelus dromedarius) was made. Whey proteins were separated by ion-exchange chromatography and identified by polyacrylamide gel electrophoresis, amino acid composition and N-terminal sequence determination. The main components of wheys of yak and khainak were nearly identical with their bovine counterparts. Three different forms of α-lactalbumin were isolated in the whey of Camelus bactrianus and two from Camelus dromedarius. As shown by classical biochemical and immunological studies, β-lactoglobulin was absent from whey of both Camelus. Camel whey basic protein (CWBP), having no analogy with known milk and nonmilk proteins, was identified in the whey of Camelus bactrianus and Camelus dromedarius and its N-terminal sequence was determined.     

PURIFICATION AND CHARACTERIZATION OF ALKALINE PROTEINASES FROM THE VISCERA OF ANCHOVY, ENGRAVLIS JAPONICA

Two electrophoretically homogeneous proteinases designated proteinase A and B were isolated from anchovy viscera. Purity was increased 17.7 and 24.6-fold with approximately 1.9 and 1.8% yield for proteinases A and B, respectively. The maximum caseinolytic activity was found to be at pH 9.4 for proteinase A and at pH 9.6 for proteinase B at the optimum temperature of 48°C. The molecular weights of proteinase A and B were determined to be 27, 300 and 25,100 D, respectively, using Sephadex G-100 gel filtration. The amino acid profiles of the enzymes were similar and relative proportion of amino acid residues was comparable to that in bovine pancreatic α-chymotrypsin. Proteinase A and B were identified as α-chymottypsin-like serine proteases by inhibitor and substrate specificity studies. Apparent K_m (K_m′) values of proteinase A and B for benzoyl-L-tyrosine ethyl ester were 4.6 × 10_?4 M and 1.2 × 10_?3 M, respectively.     

PURIFICATION AND CHARACTERIZATION OF THREEISOZYMES OF PECTIN METHYLESTERASE FROM TOMATO FRUIT

Three isozymes of pectin methylesterase (EC 3.1.1.11) have been purified to homogeneity from tomato (var. S. marzano). The isozymes were separated by affinity chromatography on Heparin-Sepharose column. They exhibited a molecular mass of 31 kDa when analyzed in sodium dodecyl sulfate gel electrophoresis and of 35 kDa in gel-filtration chromatography in native conditions. The isoelectric points of all three isozymes were found to be higher than 9.3. The K_ms calculated for the three isozymes were different toward citrus pectin used as substrate; one had a K_m of 9.7 mM (by expressing the pectin concentration as mmoles/L of methoxy groups) and the other two had similar K_ms of 3.0 and 2.6 mM, respectively. The isozyme having the higher K_m for substrate was inhibited by citrus pectin (which had a degree of methylation of 70%) at concentrations higher than 5 mM, but no inhibition was found using a pectin with a degree of methylation of 30% at concentrations up to 13 mM (i.e. 9 mg/ml) with a K_m of 14.7 mM. Furthermore, this isozyme showed a more broad range of activity in a pH range 5–10 with respect to that exhibited by the other two isozymes. All three isozymes were found to be glycosylated, although to different extents.