丙酸杆菌素抑菌效果评价及在芽菜保鲜中的应用

研究谢氏丙酸杆菌(Propionibacterium shermanii,CICC10019)发酵过程中产生丙酸杆菌素对食源性致病菌及芽菜内生菌的抑菌效果。将丙酸杆菌素溶液发酵液用于绿豆芽保鲜,评价了其对绿豆芽菌落总数、pH和挥发性盐基氮的影响。结果表明:谢氏丙酸杆菌发酵时间为120 h时,产酸最多,pH为4.52,还原糖总量消耗大,发酵液抗菌活性最高;丙酸杆菌素溶液对金黄色葡萄球菌(Staphylococcus aureus,ATCC6538)、大肠杆菌(Escherichia coli,ATCC35401)、枯草芽孢杆菌(Bacillus subtilis,ATCC9372)、志贺氏菌(Shigella,ATCC12022)、沙门氏菌(Salmonella,ATCC14028)和副溶血性弧菌(Vibrio Parahemolyticus,ATCC17802)均产生显著的抑菌效应,对阪崎肠杆菌(E.sakazakii)没有抑制作用。用丙酸杆菌素溶液清洗绿豆芽,可将豆芽菌落总数降低1.20 lg CFU/g;4℃保存第10 d时处理过的豆芽pH为6.20,比对照组降低了1.60;挥发性盐基氮含量为28.70 mg/100 g,为对照组的50%。冷藏条件下芽菜保质期延长了2 d。     

绿豆皮中黄酮类化合物提取工艺

研究了绿豆总黄酮的提取工艺。通过对固液比、乙醇体积分数、提取温度与提取时间的单因素实验确定水平点,设计4因素3水平实验,选用L9（3^4）正交表,优选绿豆总黄酮的最佳提取工艺为固液比1：50,φ（乙醇）为40％,提取温度70℃,提取时间120min。在此基础上得到绿豆皮中总黄酮的提取量为27．57mg／g,且5次平行的相对标准偏差为0．75％,总黄酮的平均回收率达97．5％。     

Effect of cations on the structure of mung bean cytoplasmic ribosomes

The importance of the absolute and relative concentrations of monovalent and divalent cations and centrifugal speed (pressure) in the dissociation of mung bean 80S ribosomes has been examined. In the absence of Mg²⁺ ions, ribosome monomers yield 47S and 34S particles. Fixation with glutaraldehyde, however, indicates that this dissociation pattern is largely dependent upon high pressures developed during centrifugation and that in the absence of such artifacts the immediate product of Mg-free conditions is a 74S particle. Since 74S particles rapidly revert to the 80S form when Mg is replaced, this would appear to be a conformational change. Ribosomes were also dissociated in the presence of Mg²⁺ ions if the K⁺ ion concentration was raised. Three major particles were produced, 38S and 49S from the small ribosomal sub-unit and 60S from the large sub-unit. A proportion of the 80S monomer population is more resistant to dissociation. Experiments with puromycin indicate that the more resistant fraction probably represents ribosomes completed with nascent polypeptide resulting from polysome breakdown.     

Optimization for high-density cultivation of heterotrophic Chlorella based on a hybrid neural network model

AIMS: The purpose of this study was to develop a reliable hybrid neural network (HNN) model for heterotrophic growth of Chlorella, based on which optimization for fed-batch (FB) cultivation of Chlorella may be successfully realized. METHODS AND RESULTS: Deterministic kinetic model was preliminarily developed for the optimization of FB cultivation of Chlorella. The highest biomass concentration and the maximum productivity were obtained as: 104.9 g l(-1) dry cell weight and 0.613 g l(-1) h(-1), respectively. After several cultivations had been performed, an HNN model was developed. The efficiency of biomass production was further increased by the optimization using this model. The highest biomass concentration and the maximum productivity attained was: 116.2 g l(-1) dry cell weight and 1.020 g l(-1) h(-1), respectively. CONCLUSION: The HNN model agreed well with experimental results in different cultivations. Comparison between the HNN model and the deterministic model showed that the former had better generalization ability, which made it a reliable tool in modelling and optimization. SIGNIFICANCE AND IMPACT OF THE STUDY: The high cell density and productivity of biomass obtained in this study is of significance for the commercial cultivation of Chlorella. The simple and efficient optimization strategy proposed in this paper may be employed in heterotrophic mass culture of Chlorella as well as other similar organisms.     

Changes in the forms of invertase during germination of mung bean seeds

High levels of ‘alkaline’ invertase activity occur in dormant mung bean seeds. During germination this activity decreases rapidly and is replaced by high ‘acid’ invertase activity. Cycloheximide prevented the formation of the latter activity and also inhibited germination. It is suggested that de novo synthesis of ‘acid’ invertase occurs during germination. Both enzymes bind to concanavalin A and, hence, are presumed to be glycoproteins. Affinity-purified enzyme samples show similar ratios of ‘acid’ and ‘alkaline’ invertase activities to the crude preparations indicating that specific enzyme inhibitors or activators are probably not involved in controlling the activities in vivo.     

Purification and partial characterization of an aminopeptidase from mung bean cotyledons

An aminopeptidase (EC 3.4.11.-) was purified to homogeneity, as judged by SDS-PAGE. from mung bean ( Vigna radiata ) cotyledons. The molecular mass of this peptidase was estimated as 75 kDa by gel filtration. When an oligopeptide consisting of 5 amino acid residues was used as substrate, amino acids were released in the order of the N-terminal sequence of the oligopeptide chain. This enzyme apparently requires free sulfhydryl for its activity, as judged by the effects of various proteinase inhibitors. Among aminoacyl- p -nitroanilides examined for the availability as substrates of the enzyme, p -nitroanilides with hydrophobic amino acids were preferred substrates. According to western immunoblot profiles, the enzyme level in cotyledons was high at the early stage of imbibition and declined rapidly after germination.     

The effect of brassinolide on the light-induced growth inhibition in mung bean epicotyl

Growth of the mung bean (Vigna radiata L.) epicotyl was retarded by white (400–700 nm) light, especially by monochromatic red (660 nm) light. Growth promoting effects of brassinolide were observed under those light conditions that retarded growth, but were not evident in the dark or under far-red light. Brassinolide seems to act to overcome the inhibitory affects of lights.     

An inhibitor of phosphoinositol kinase from ungerminated mung bean seeds

A protein inhibitor of phosphoinositol kinase has been detected in the later stages of ripening of mung bean seeds. This has been isolated and purified from the ungerminated seeds. It migrated as a single protein band when subjected to polyacrylamide gel electrophoresis. The MW of the inhibitor is approx. 86 000. The phosphoinositol kinase inhibition has been found to be dependent on the protein concentration of the purified inhibitor. It seems that 1 molecule of the inhibitor is necessary to inhibit 1 molecule of enzyme. The nature of the inhibition has been found to be non-competitive, the K_i of which is around 1·47 × 10^?6 M. The enzyme inhibitor complex dissociates on gel electrophoresis without any loss of enzyme activity.     

Internalization of bioluminescent Escherichia coli and Salmonella Montevideo in growing bean sprouts

AIMS: Investigate the interaction of bioluminescent Escherichia coli and Salmonella Montevideo with germinating mung bean sprouts. METHODS AND RESULTS: E. coli or Salm. Montevideo introduced on mung beans became established both internally and externally on sprouts after the initial 24 h germinating period. In both cases the inoculated bacterium formed the predominant microflora on the sprouted beans throughout. From the bioluminescent profile of inoculated sprouting beans, bacterial growth was found to be in close proximity to the roots but not on the hypocotyls. Clumps (biofilms) of cells with low viability were observed within the grooves between epidermal cells on hypocotyls. Treatment with 20,000 ppm sodium hypochlorite removed the majority of bacteria from the surface of hypocotyls although nonviable single cells were occasionally observed. However, viable bacteria were recovered from the apoplastic fluid, and extracts of surface-sterilized sprouts indicating that the internal bacterial populations had been protected. This was confirmed using in situ beta-glucuronidase staining of surface-sterilized sprouts where cleaved enzyme substrate (by the action of internalized E. coli) was visualized within the plant vascular system. CONCLUSIONS: E. coli or Salmonella present on seeds become internalized within the subsequent sprouts and cannot be removed by postharvest biocidal washing. SIGNIFICANCE AND IMPACT OF THE STUDY: Mung bean production should be carefully controlled to prevent contamination occurring in order to minimize the health risk associated with raw bean sprouts.     

Inhibitory effect of polyamines on the activity of endopeptidase in mung bean cotyledons

The activity of cysteine endopeptidase (EP) in the cotyledons of mung bean seeds increased with time after germination. When cotyledons were excised from the embryonic axis in the course of seedling growth, the activity of EP in the excised cotyledon markedly dropped during the following incubation of 1 d. However, the level of EP protein in excised cotyledons, as examined by immunoblotting, was similar to that in axis-attached cotyledons at the corresponding stage. Thus, it seems that the low activity of EP in excised cotyledons is not due to a decrease in the content of EP protein, but due to a loss of the activity of existing EP. Treatment of attached cotyledons with polyamines (PAs; putrescine and spermidine [Spd]) resulted in a decrease in EP activity, while the same PA-treatment brought about little alteration in the level of EP protein. This indicates that PAs somehow produce an inhibitory effect on the activity of EP. Axis-removal resulted in an accumulation of Spd in the cotyledon. The possibility is suggested that PA, especially Spd, is involved in the inhibition of EP activity in excised mung bean cotyledons.     

胃蛋白酶水解绿豆分离蛋白的工艺

选用胃蛋白酶对绿豆分离蛋白进行酶法水解,考察了原料预处理条件、pH、温度、底物浓度等对酶解的影响,结果表明：原料预处理最适条件为沸水浴中90℃处理20min,在37℃、pH1．8、底物质量分数7％、酶量6000U／g条件下酶解180min,水解度（DH％）为19．86％,达到了制备小肽的水解度要求。实验证明,经过水解,绿豆分离蛋白各功能特性得到很好的改善。     

Molecular assessment of genetic diversity in mung bean germplasm

RAPD profiles were used to identify the extent of diversity among 54 accessions of mung bean that included both improved and local land races. Out of the 40 primers screened, seven primers generated 174 amplification products with an average of 24.85 bands per primer. The RAPD profiles were analysed for Jaccard's similarity coefficients that was found to be in the range from 0 to 0.48, indicating the presence of wide range of genetic diversity at molecular level. Cluster analysis was carried out based on distances (1-similarity coefficient) using neighbour-joining method in Free Tree package. The dendrogram resolved all the accessions into two major clusters, I (with 11 accessions) and II (with 43 accessions). However, the cluster was further divided into four subclusters (II A with six, II B with nine, II C with 15 and II D with 13 accessions). The distribution of the accessions in different clusters and subclusters appears to be related to their performance in field conditions for 10 morphological traits that were scored. This study indicated that the RAPD profiles provide an easy and simple technique for preliminary genetic diversity assessment of mung bean accessions that may reflect morphological trait differences among them.     

次氯酸钠真空处理绿豆消毒效果评价及机理研究

本研究讨论了绿豆中微生物的分布规律及相关联的结构特征,次氯酸钠常规及真空处理绿豆全豆、表皮及内部消毒效果的评价及机理分析.结果证明,绿豆全豆、表皮及内部的菌落总数分别为8.41×105cfu/g、6.70×103 cfu/g及8.30×105cfu/g,经有效氯浓度为(3 000～33 000)mg/kg的次氯酸钠溶液,1h常规浸种处理后绿豆全豆、表皮及内部菌落总数分别下降(0.93～2.22) log cfu/g、(0.92 ～ 2.20) log cfu/g及(0.94 ～ 2.09) log cfu/g.真空度0.05 MPa下,经有效氯浓度(3 000 ～ 33 000) mg/kg的次氯酸钠溶液1h浸泡后,绿豆全豆、表皮及内部菌落总数分别下降(1.67 ～ 4.15) log cfu/g、(1.15 ～2.38)1og cfu/g及(1.62～4.11) log cfu/g.经分析,真空处理能使次氯酸钠克服绿豆表皮蜡质层及内部空腔结构的影响,有效接触微生物从而提高消毒效果.     

Kinetic properties of IAA oxidase from mung bean cotyledons

A crude enzyme preparation from mung bean cotyledons was separated into peroxidative and non-peroxidative IAA oxidase on a DEAE-cellulose column. Both fractions differed in their pH optima, K_m and V_max. The K_m and V_max of non-peroxidative IAA oxidase were higher than those of peroxidative IAA oxidase. Peroxidative IAA oxidase showed a linear increase in absorption at 247 and 254 nm after a short lag of 2–3 min. The addition of catalytic amounts of hydrogen peroxide eliminated the lag period and also enhanced the rate of IAA degradation. The non-peroxidative IAA oxidase fraction, however, did not exhibit any significant increase in absorption at 247 and 254 nm and showed a lag period of 5 min which was not affected by hydrogen peroxide. Instead, addition of the same catalytic amount of hydrogen peroxide inhibited the rate of IAA degradation. The peroxidative IAA oxidase fraction exhibited the reaction kinetics characteristic of peroxidase-catalysed IAA degradation. The rate of IAA oxidation by purified non-peroxidative IAA oxidase was very low. The slow rate of catalysis shown by non-peroxidative IAA oxidase appears to be due to the presence of inhibitor(s).     

Multivesicular bodies in developing tobacco seed and mung bean are functionally equivalent

Protein storage vacuoles (PSVs) are the primarily storage organelles in cotyledon cells for protein preservation in seeds. Storage proteins are transported from the endoplasmic reticulum (ER) to the Golgi apparatus for subsequent delivery to PSVs via presumably Golgi-derived dense vesicles (DVs). However, recent studies demonstrated that storage proteins in early stage of developing cotyledon of mung beans reached the multivesicular bodies (MVBs) prior to the detection of DVs, indicating the possible involvement of MVBs in mediating transport of storage proteins during the early stage of seed development. Here, we further show that the MVBs in developing tobacco seeds are functionally and biochemically equivalent to those in developing mung beans. Thus, MVBs in developing tobacco seeds are structurally distinct from DVs, contain both vacuolar sorting receptors (VSRs) and storage proteins, and they are insensitive to treatments of wortmannin and brefeldin A (BFA).     

Regulation of sterol biosynthesis in etiolated mung bean hypocotyl sections

The incorporation of radioactivity into sterols by transmethylation of methionine-[¹⁴C-methyl] was studied in mung bean hypocotyl sections. Young hypocotyl sections (1 cm) synthesized 4 times more radioactive sterols than older sections (5 cm). The transmethylation reactions may be rate limiting in older tissues. Wounding has only a quantitative effect on sterol biosynthesis, as seen by incorporation experiments with MVA-[2-¹⁴C]. Naphthalene acetic acid (NAA) stimulates sterol biosynthesis in both wounded surfaces and intact tissues of mung bean hypocotyl sections.     

Purification and characterization of extracellular invertase from the hypocotyls of mung bean (Phaseolus radiatus L.)

The extracellular invertase (β-D-fructofuranoside fructohydrolase, EC 3.2.1.26) was isolated and characterized from the hypocotyls of mung bean (Phaseolus radiatus L.). The enzyme was purified to apparent homogeneity by ammonium sulfate fractionation and sequential chromatography over diethylaminoethyl (DEAE)-cellulose anion exchange, Concanavalin (Con) A-Sepharose 4B affinity and Sephadex G-200. The overall purification was about 77-fold with a recovery of about 11%. The finally purified enzyme exhibited a specific activity of about 113 μmol of glucose produced mg^-1 protein min^-1 at pH 5.0 and appeared to be a single protein by nondenaturing polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The enzyme had the native molecular mass of 134 kD and subunit molecular weight of 67 kD as estimated by Sephadex G-200 chromatography and SDS-PAGE, respectively, suggesting that the enzyme was composed of homodimeric proteins. On the other hand, the enzyme appeared to be a glycoprotein containing mannosyl residues on the basis of its ability to interact specifically with the immobilized Con A and the separability of invertase-Con A complex by methyl-α-D-mannopyranoside. The enzyme had a K_m for sucrose of 3.4 mM and its pH optimum of 4.0. The enzyme showed highest enzyme activity with sucrose as substrate. Raffinose and cellobiose were hydrolyzed at a low rate, maltose and lactose were not cleaved by the enzyme. These results indicate the extracellular invertase is a β-fructofuranosidase.     

Further characterization of phosphoinositol kinase isolated from germinating mung bean seeds

Phosphoinositol kinase isolated and purified from germinating mung bean seeds has been further characterized. The rate of phosphorylation varies with different inositol phosphates and this is consistent with the K_m and V_max for each of the substrates. The phosphate transfer from ATP has been found to be mediated by a phosphoprotein intermediate. In a particular step of the reaction the immediate product of the reaction has been found to be most inhibitory, other products being less or non-inhibitory. The inhibition has been found to be competitive in nature. The K_is have been found to range between 0.6 and 1 × 10^?4 M. ADP also inhibited non-competitively with respect to IP₅. K_i for this has been found to be 2.3 × 10^?4 M. The purified enzyme migrated as a single protein band on polyacrylamide gel electrophoresis. In the presence of sodium dodecyl sulphate it is dissociated into 3 subunits in the ratio 1 : 1 : 1. The MW of the three subunits are approx. 86 000, 56 000 and 35 000. The MW of the enzyme has been found to be approx. 177 000.     

铅对绿豆幼苗生长的影响

Effects of Pb^2 on the growth of mung bean(Phaseolus radiatus L.)seedlings were conducted with an experiment.The results showed that the dry weight of roots increased by 13.01%,the dry weight of shoots decreased by 12.80%,the free proline and MDA content in leaves increased specially by 2.07% and 5.82%,the activity of POD decreased by 37.32% compared to control under 0.05mmol/L Pb^2 treatment.Under 0.5mmol/L Pb^2 treatment,the dry weights of roots and shoots decreased specially be 14.45% and 29.36%,the free proline and MDA content in leaves increased specially by 43.55% and 28.50,the activity of POD decreased by 59.37% compared to control.The results indicated that Pb^2 interfered the growth of mung bean seedlings by destroying cell membrane intergrity and decreasing the activity of POD in leaves.