Recombinant expression of black sesame polyphenol oxidase and its enzymatic properties / 生物工程学报

To investigate the enzyme properties of the black sesame polyphenol oxidase (BsPPO), a synthesized Bsppo gene was cloned into the vector pMAL-c5x and expressed in E. coli. Subsequently, the MBP fusion label in the recombinant protein was removed by protease digestion after affinity purification. The synthesized Bsppo gene contained 1 752 bp which encodes 585 amino acids with a deduced molecular weight of 65.3 kDa. Transformation of the recombinant vector into E. coli BL21(DE3) resulted in soluble expression of the fusion protein MBP-BsPPO. The enzymatic properties of the recombinant BsPPO was investigated after MBP fusion tag excision followed by affinity purification. The results demonstrated that the optimal temperature and pH for BsPPO was 25°C and 4.0, respectively. BsPPO exhibited a good stability under low temperature and acidic environment. Low-intensity short-term light exposure increased the activity of BsPPO. Cu²⁺ could improve the activity of BsPPO while Zn²⁺ and Ca²⁺ showed the opposite effect. BsPPO could catalyze the oxidation of monophenols, diphenols, and triphenols, and exhibited good catalytic activity on l-tyrosine and vanillic acid. Moreover, BsPPO exhibited high catalytic activity on black sesame metabolites, including 2-methoxy cinnamic acid, indole-3-carboxylic acid and phloretin. These results may serve as a basis for further characterization of BsPPO.

Content determination of phenolic acids in fresh Salvia miltiorrhiza and effect of polyphenol oxidase on content / 中国中药杂志

There is no consensus on the content, accumulation, transformation and content determination methods of phenolic acids in fresh Salvia miltiorrhiza. In order to find out the true content of phenolic acids in fresh S. miltiorrhiza, a variety of treatment me-thods were used in this study to prepare sample solution. The content changes of phenolic acids in S. miltiorrhiza samples with different dehydration rates were investigated during drying and shade drying processes. Polyphenol oxidase(PPO) of S. miltiorrhiza was extracted and purified by ammonium sulfate precipitation and dialysis to investigate the enzymatic properties. The content of rosmarinic acid, lithosperic acid and S. nolic acid B in S. miltiorrhiza was determined by UPLC. The results showed that the content of phenolic acids in fresh S. miltiorrhiza was highest when it was homogenized with 1 mol·L~(-1) HCl solution or 1 mol·L~(-1) HCl methanol solution. There was no significant difference in the content of phenolic acids in S. miltiorrhiza with different dehydration rates, indicating that there was no correlation between phenolic acid content and dehydration rate. The optimum pH of S. miltiorrhiza PPO was 7.6 and the optimum temperature was 40 ℃. With catechol as substrate, S. miltiorrhiza PPO had the enzymatic browning reaction which was in compliance with Michaelis equation, with Michaelis constant K_m of 0.12 mol·L~(-1) and V_(max) of 588.23 U·min~(-1). The inhibitory effect of citric acid, disodium ethylenediamine tetraacetate, ascorbic acid and sodium sulfite on S. miltiorrhiza PPO increased with the increase of inhibitor concentration, and sodium sulfite showed the strongest inhibitory effect. The present study proved that there were a large number of phenolic acids in fresh S. miltiorrhiza, which were the secondary metabolite of primitive accumulation during the growth of S. miltiorrhiza, rather than the induced product of postharvest drying and dehydration stress. This study has reference value and significance for the cultivation, harvest and processing of S. miltiorrhiza.

Determination of the activity and kinetic parameters of polyphenol oxidase enzyme in crude extracts of some Jordanian plants

The activity and kinetic parameters of the enzyme polyphenol oxidase (PPO) in crude extracts of the fruits ofParadise apple (Pyrus malus L.), cucumber (Cucumis sativus L.), squash (Cucurbita pepo L.), pomegranaterind and seeds (Punica granatum L.), and the leaf of cactus (Opuntia ficus-indica (L.) were investigated. Thehighest browning intensity was found in P. apple, followed by pomegranate seeds and cucumber fruits. Theoptimum activity of the enzyme was shown at pH 7.0 for P. apple and cucurbita, but it was found at pH 6.0 forthe rind and seeds of the pomegranate. The PPO of cactus leaf and cucumber fruits showed two peaks at pH 4.0and 7.0. On the other hand, the optimal temperature found for PPO activity in these plants was around 40°C.A strong correlation with value (R) = 0.9485 between the browning intensity and PPO activity in all studiedsamples was obtained.

Screening and verification of proteins of Salvia miltiorrhiza polyphenol oxidase interaction / 中国中药杂志

Polyphenol oxidase(PPO) is an important antioxidant enzyme in plants. It has the functions of scavenging active oxygen and synthesizing phenols, lignin, and plant protection factors, and can enhance the plant's resistance to stress and resistance to pests and diseases. Our previous research found that Salvia miltiorrhiza PPO gene can positively regulate salvianolic acid B synthesis. In order to further explore the mechanism, a pGBKT7-PPO bait vector was constructed using the cloned S. miltiorrhiza polyphenol oxidase gene(SmPPO, GenBank accession number: KF712274.1), and verified that it had no self-activation and no toxicity. The titer of S. miltiorrhiza cDNA library constructed by our laboratory was 4.75 × 107 cfu·mL~(-1), which met the requirements for library construction. Through yeast two-hybrid test, 22 proteins that could interact with SmPPO were screened. Only yeast PAL1 and TAT interacted with SmPPO through yeast co-transformation verification. Further verification was performed by bimolecular fluorescence complementary detection(BiFC). Only TAT and SmPPO interacted, so it meant that TAT and SmPPO interacted. TAT and SmPPO were truncated according to the domain, respectively. The first 126 amino acids of SmPPO and tyrosine amino transferase(TAT) were obtained to interact on the cell membrane and chloroplast. SmPPO was obtained by subcellular localization test, which was mainly loca-lized on the nucleus and cell membrane; TAT was localized on the cell membrane. Real-time quantitative PCR results showed that the SmPPO gene was mainly expressed in roots and stems; the TAT gene was expressed in roots, and the expression level in stems and flowers was low. This article lays a solid foundation for the in-depth study of the molecular mechanism of the interaction of S. miltiorrhiza SmPPO and TAT to regulate the synthesis of phenolic substances.

Efecto de la procedencia y el almacenamiento en la calidad del café / Effect of provenance and storage on coffee quality

Resumen Antecedentes. La calidad del grano de café ha sido relacionada con su procedencia, su manejo agronómico y sus condiciones de almacenamiento. Objetivo. Determinar la actividad de la polifenil oxidasa, el contenido de lípidos, el color y las características organolépticas de cafés provenientes de 3 subestaciones experimentales. Materiales y métodos. Se siguió un diseño completamente aleatorio en arreglo factorial factorial 3x6 (lugares de procedencia del café y tiempo de almacenamiento respectivamente). Resultados. La actividad de la polifenil oxidasa es mayor en el café fresco-para las tres procedencias. El café procedente de Naranjal presentó actividades enzimáticas más altas que los cafés provenientes de las subestaciones Supía y la Catalina. El análisis de varianza mostró el efecto de la procedencia sobre la variable actividad enzimática. La actividad de la polifenil oxidasa en los cafés estudiados decrece con el tiempo de almacenamiento. El contenido de lípidos es menor a menor en la subestación de la Catalina. Todos los cafés fueron caracterizados de buena calidad en el tiempo cero de almacenamiento. Las características de aroma, intensidad del aroma y cuerpo presentaron altibajos en los diferentes meses de almacenamiento. El café de Naranjal, obtuvo en promedio una calificación aceptable a lo largo de los seis meses de almacenamiento. Conclusiones. Se encontraron diferencias significativas para las variables estudiadas por efecto de la procedencia y el almacenamiento. La actividad enzimática de la PFO presentó etapas de activación/inhibición, durante los seis meses de almacenamiento.

Abstract Background. The quality of the coffee bean has been related to its origin, the agronomic management and the storage conditions. Objective. To determine the activity of the polyphenyl oxidase, the lipid content, the color and the organoleptic characteristics of coffees from 3 experimental substations. Materials and methods. A completely randomized design was followed in a 3x6 factorial arrangement (places of coffee origin and storage time respectively). Results. The activity of polyphenyl oxidase is greater in fresh coffee-for the three provenances. The coffee from Naranjal presented higher enzymatic activities than the coffees from the Supía and the Catalina substations. The analysis of variance showed the effect of provenance on the enzyme activity variable. The activity of the polyphenyl oxidase in the coffees studied decreases with storage time. The lipid content is lower at a lower height in the Catalina. All coffees were characterized as good quality at zero storage time; but the characteristics of aroma, intensity of aroma and body presented ups and downs in the different months of storage. Naranjal coffee, on average, obtained an acceptable rating throughout the six months of storage. Conclusions. Significant differences were found for the variables studied due to the effect of provenance and storage. The enzymatic activity of the PFO showed activation / inhibition stages, during the six months of storage.

Combined effect of pseudomonas sp. and trichoderma aureoviride on lettuce growth promotion / Efeito combinado de Pseudomonas sp. e Trichoderma aureoviride na promoção do crescimento de alface

Plant growth promotion by microorganisms may be a viable alternative to increase lettuce production through pathogens control and nutrients absorption increase. Trichoderma and Pseudomonasgenus are examples of widely studied microorganisms with the capacity to promote plant growth. However, there are still gaps regarding the action of the combined effect of these two microorganisms. Therefore, the objective of this study was to evaluate the combined effect of Pseudomonas sp. UAGF14 and Trichoderma aureoviride URM5158 on the development of lettuce plants. The experimental design was completely randomized, with five treatments: CONT (control), CM (soil with organic fertilization), CMB (soil withorganic fertilization and Pseudomonas sp.), CMF (soil with organic fertilization and T. aureoviride), and CMFB (soil with organic fertilization, Pseudomonas sp. and T. aureoviride), with ten repetitions. At 30, 40 and 60 days after sowing, the following parameters were analyzed: plant and canopy height and number of leaves. At 60 days after emergence, shoot dry matter, leaf area, root dry matter, root length and chlorophyll were analyzed. Catalase, peroxidase and polyphenol oxidase enzymatic activity were determined. The CMFB treatment had the highest means of lettuce growth promotion, confirming the synergistic effect of the combination of the two microorganism types, as it increased height, canopy, shoot and root dry matter, and chlorophyll levels compared to CONT, although did not differ from CM in some variables. Enzymatic activity was also influenced by the action of these microorganisms combined, evidencing by polyphenol oxidase increase. The CMFB or CM were efficient in promoting lettuce growth, showing positive response to the plant morphological and physiological characteristics. However, few responses were observed in lettuce plant growth in the first cycle evaluated after 60 days, compared CM and CMFB treatments, but both treatments showed superiority in lettuce plant growth submitted to CONT treatment. Therefore, further studies are needed to estimate the long-term effects of combined effect of Pseudomonas sp. UAGF14 and T. aureoviride URM5158 on crop productivity in field conditions.

A promoção do crescimento das plantas por micro-organismos pode ser uma alternativa viável para aumentar a produção de alface através de controle de patógenos e aumento da absorção de nutrientes. O gênero fúngico Trichoderma e o gênero bacteriano Pseudomonas são exemplos de micro-organismos amplamente estudados com capacidade para promover o crescimento da planta. No entanto, ainda existem lacunas quanto à ação do efeito combinado desses dois micro-organismos. Portanto, o objetivo deste estudo foi avaliar o efeito combinado de Pseudomonas UAGF14 e Trichoderma aureoviride URM5158 sobre o desenvolvimento de plantas de alface. O delineamento experimental foi completamente casualizados, com cinco tratamentos: CONT (controle, sem fertilização orgânica), CM (solo com fertilização orgânica), CMB (solo com fertilização orgânicae Pseudomonas sp.), CMF (solo com fertilização orgânica e T. aureoviride) e CMFB (solo com fertilização orgânica, Pseudomonas sp. e T. aureoviride), com dez repetições. Aos 30, 40 e 60 dias após a semeadura, foram analisados os seguintes parâmetros: altura da planta e dossel e número de folhas. Aos 60 dias após a emergência, a matéria seca da parte aérea, a área foliar, a massa seca das raízes, o comprimento radicular e a clorofila foram analisados. Catalase, peroxidase e atividade enzimática da polifenol oxidase foram determinadas. O CMFB apresentou o maior crescimento de alface, confirmando o efeito benéfico da combinação dos dois tipos de micro-organismos com a planta, na medida em que aumentou a altura, o dossel, a matéria seca da parte aérea e da raiz, e os níveis de clorofila em relação ao CONT, embora não tenha diferido do CM em algumas variáveis. As atividades enzimáticas também foram influenciadas pela ação desses micro-organismos combinados, evidenciada pelo aumento de polifenol oxidase. O CMFB ou CM foram eficientes na promoção do crescimento da alface, mostrando respostas positivas às características morfológicas e fisiológicas. Entretanto, poucas respostas foram observadas no crescimento da alface noprimeiro ciclo da planta avaliado depois de 60 dias, comparando os tratamentos CM e CMFB, mas ambos tratamentos mostraram superioridade em relação ao crescimento das plantas de alface submetidas ao tratamento controle. Por isso, são necessários futuros estudos para estimar à longo prazo o efeito combinado de Pseudomonas sp. UAGF14 e Trichoderma aureoviride URM5158 na produção de cultura em condições de campo.

Phenotypic Characterization and Synthesis of Extracellular Catecholase from a Newly Isolated Bacterium Pseudomonas sp. BSC-6

Abstract Catecholase (EC 1.10.3.1), an oxidoreductase enzyme is a key member of polyphenol oxidase family which catalyze the degradation of catechol. This enzyme possesses vast applications in diverse areas and is found in bacteria, fungi, mushrooms, higher plants, arthropods, amphibians and mammals. Catechol, a phenolic compound, is used as a starting material in the synthesis of various industrial compounds such as inhibitors, antioxidants, pesticides etc. The release of this phenolic compound in the environment causes toxicity to both flora and fauna. In the present studies, emphasis has been laid on isolation, screening and characterization of catechol degrading bacterium coupled with synthesis of catecholase enzyme. Further, the selected isolated strain was phenotypically characterized and was found to be member of genus Pseudomonas. Among all the isolates, BSC-6 was found as best isolate with maximum extracellular catecholase activity of 152.32 IU/L obtained after scale up studies. The herein synthesized bacterial catecholase may be employed for wide applications particularly in bioremediation of phenol enriched polluted sites.

Effect of Blanching on Enzyme Activity and Bioactive Compounds of Blackberry

ABSTRACT The inactivation of peroxidase and polyphenol oxidase and the degradation of phenolic compounds, anthocyanins, and antioxidant activity in blackberry were investigated during blanching in water at 80-90 °C, and in steam, from 0 to 10 minutes. The enzyme kinetics indicated the presence of two isoenzymes with different thermal stability, following two-phase model, in which the reaction rate constant increased with increasing temperature for both the heat labile and heat resistant component. The phenolic compounds also followed a biphasic pattern, indicating a more heat resistant fraction, and the rate constants increased with increasing temperature. For the antioxidant activity and anthocyanins, the first order kinetic model (R2>0.982) indicated an increase in degradation rate constants with temperature, from 0.050 to 0.137min-1 for DPPH, 0.085 to 0.285min-1 for ABTS, and 0.017 to 0.052 min-1 for anthocyanins.

Induction of defense-related enzymes in patchouli inoculated with virulent Ralstonia solanacearum

Background: Defense-related anti-oxidative response is a vital defense mechanism of plants against pathogen invasion. Ralstonia solanacearum is an important phytopathogen. Bacterial wilt caused by R. solanacearum is the most destructive disease and causes severe losses in patchouli, an important aromatic and medicinal plant in Southeast Asia. The present study evaluated the defense response of patchouli inoculated with virulent R. solanacearum. Results: Results showed that the basic enzymatic activities differed not only between the leaves and stems but also between the upper and lower parts of the same organ of patchouli. POD, SOD, PPO, and PAL enzymatic activities were significantly elevated in leaves and stems from patchouli inoculated with R. solanacearum compared to those in control. The variation magnitude and rate of POD, PPO, and PAL activities were more obvious than those of SOD in patchouli inoculated with R. solanacearum. PAGE isoenzymatic analysis showed that there were one new POD band and two new SOD bands elicited, and at least two isoformic POD bands and two SOD bands were observably intensified compared to the corresponding control. Conclusion: Our results suggest that not only defense-related enzymatic activities were elevated but also the new isoenzymatic isoforms were induced in patchouli inoculated with R. solanacearum.

Subcritical Butane Extraction for Effective Removalof Abamectin in Fresh Tea Leaves / 分析化学

Subcritical butane technology was employed for the separation of abamectin on the fresh tea leaves surface.Under the conditions of solid-liquid ratio of 1∶10 (m/V), the experiment was designed via the response surface methodology and conducted at different temperature, various separation time and discrepant cycle number.Besides, the activity of the polyphenol oxidase (PPO) relating to the quality of the tea was determined and compared.At the same time, scanning electron microscopy (SEM) was used to observe the surface structure of fresh tea leaves before and after treatment, and the effect on physiological characteristics of the leaves by subcritical butane treatment was analyzed.The experimental results showed that the subcritical butane extraction could effectively isolate the abamectin, making the physical structure basically remained and the polyphenol oxidase activity preserved as well.Through the analysis by Design Expert software, the optimal processing parameters of separating abamectin were as follows: 45℃, 30 min, 1 cycle, and solid-liquid ratio of 1∶10 (m/V).Under the optimal conditions, the separation efficiency was over 91% and the relative PPO activity was 25.73%.The structure of fresh tea leaves changed insignificantly before and after the butane processing.This study suggested that the subcritical butane extraction technology could effectively remove pesticide residues in tea, thus provided a certain scientific basis for application of subcritical fluid removal of pesticide residue in natural plants.

Inhibitory effect of galangin on polyphenol oxidase and study of mechanism / 中国免疫学杂志

Objective:To investigated the activity inhibition and inhibitory type of polyphenol oxidase (PPO) induced by galangin and the interaction mechanism of galangin with polyphenol oxidase was preliminarily indicated,and prove the related mechanism of galangin on proliferation of on human melanoma A375 cells.Methods: The activity inhibition and inhibitory type of PPO induced by galangin were investigated by spectrophotometric method,and interation mechanism of galangin with PPO was preliminarily indicated by fluorescence quenching and molecular docking,and chelating copper ions with the inhibitory mechanism of galangin on polyphenol oxidase was measured.Results: Galangin was a competitive inhibitor,the IC50 and Ki on PPO were obtained to be (47.86±3.33) and (24.83±1.45)μmol/L,respectively.Fluorescence spectrum indicated the fluorescence of PPO was quenched effectively by galangin and the binding constant Ka was obtained to be (4.67±0.43)×104 L/mol.Chelating copper ions and molecular simulation further showed that galangin was combined with active center of copper ions,and formed hydrogen bonds with catalytic site His259.Luteolin could induce the apoptosis of A375 cells significantly,and the tyrosinase activity and melanin synthesis were decreased.Conclusion: Galangin as a competitive polyphenol oxidase inhibitor and reduced the activity of polyphenol oxidase.which provides the theoretical basis for the clinical anti skin cancer.

Influence of root-knot nematode infestation on antioxidant enzymes, chlorophyll content and growth in Pogostemon cablin (Blanco) Benth.

Plants adapt themselves to overcome adverse environmental conditions, and this involves a plethora of concurrent cellular activities. Physiological experiments or metabolic profiling can quantify this response. Among several diseases of Pogostemon cablin (Blanco) Benth. (Patchouli), root-knot nematode infection caused by Meloidogyne incognita (Kofoid and White) Chitwood causes severe damage to the plant and hence, the oil production. In the present study, we identified M. incognita morphologically and at molecular level using sequenced characterized amplified region marker (SCAR). M. incognita was artificially inoculated at different levels of second stage juveniles (J2) to examine the effect on Patchouli plant growth parameters. Peroxidase and polyphenol oxidase enzyme activity and changes in the total phenol and chlorophyll contents in M. incognita was also evaluated in response to infection. The results have demonstrated that nematode infestation leads to increased peroxidase activities in the leaves of the patchouli plants and thereby, increase in phenolic content as a means of defence against nematode infestation. Chlorophyll content was also found decreased but no changes in polyphenol oxidase enzyme activity.

Partial Optimization and Study of Antimicrobial Activity of Polyphenol Oxidase (PPO) and Peroxidase (POD) Extracted from Chilly Pepper Pericarp.

Polyphenol oxidase(PPO) (E.C. number 1.10.3.1) has ubiquitous distribution in almost all living organism. Whereas, peroxidase(POD) (E.C. number 1.11.1) act as hormone regulation and defense mechanism in plants. Keeping in pace with their present-day industrial application, efforts have been made to evaluate the activity of these two enzymes (PPO and POD) using pepper pericarp (Capsicum annuum L.) as an experimental material using catechol and guaiacol as a substrate, respectively. The effects of enzyme extract, substrate, hydrogen peroxide concentration (only for POD), pH and temperature and antimicrobial activity against different bacterial strains were investigated.

Estudo da aplicação da tirosinase vegetal no tratamento de efluentes e verificação da genotoxicidade do efluente tratado em células vegetais / Study on tyrosinase application in the treatment of plant effluent and verification of genotoxicity of the treated effluent into plant cells

Os problemas ambientais relacionados à crescente atividade industrial têm gerado preocupações aos órgãos governamentais e entidades de proteção ambientais, sendo necessários estudos de base que busquem novas alternativas para a recuperação de áreas poluídas e a solução de problemas operacionais relacionados com as técnicas empregadas. Um dos compostos mais encontrados em diversos efluentes industriais, principalmente de indústrias bioquímico-farmacêuticas, é o fenol que provoca um impacto danoso no ambiente devido ao fato de ser um poluente tóxico. O presente trabalho propõe, portanto, avaliar a oxidação e destruição do fenol através da utilização da enzima tirosinase extraída de vegetais, cujos resultados podem ser úteis para o tratamento de outros compostos fenólicos como o hormônio 17β-estradiol ou os que se encontram nos efluentes procedentes da produção de azeite ("águas de vegetação") após a recuperação dos polifenóis importantes como antioxidantes. A tirosinase tem a capacidade de transformar fenóis em produtos menos solúveis em água e menos danosos, permitindo assim uma agressão menor ao ambiente. Outro método de remoção do fenol também foi avaliado utilizando queratina extraída de penas de galinha, quitina e quitosana como bioadsorventes. A atividade enzimática foi determinada espectrofotometricamente com soluções de fosfato de potássio e L-tirosina. Para determinar a concentração de fenol aps a oxidação foi utilizada a Cromatografia Líquida de Alta Eficiência (HPLC). Para estudar a adsorção do fenol aplicou-se o método colorimétrico a partir das soluções de tampão borato, 4 aminoantipirina e ferricianeto de potássio e as absorbâncias foram lidas em espectrofotômetro UV-Vis a 546nm, enquanto a determinação de polifenis presentes na "água de vegetação" foi realizada pelo método Folin-Ciocalteu. A quantidade de tirosinase nas batatas das variedades Ágata e Galette di Bologna apresentou-se muito baixa a ponto de modificarmos a matéria prima para...

Environmental problems related to growing industrial activity have generated concerns among government entities and environmental protection, being necessary more baseline studies that seek new alternatives for the recovery of polluted areas and solution of problems related to the operational techniques employed. One of the compounds most commonly found in many industrial effluents, mainly from biochemical and pharmaceutical industries, is phenol, which causes a detrimental impact on the environment due to its toxicity. Therefore, this work proposes the oxidation and destruction of phenol using the enzyme tyrosinase, extracted from plants, whose results could be useful in the future for the treatment of other phenolic compounds such as 17β-estradiol hormone or those found in the effluent coming from the production for olive oil ("vegetation water") after polyphenols recovery. Such an enzyme has the ability of transforming phenols into products less soluble in water and less dangerous, thereby allowing for a minor impact on the environment. Another method of phenol removal was also evaluated using keratin extracted from chicken feathers, chitin and chitosan as phenol biosorbents. Potassium phosphate buffer and L-tyrosine solutions were used for the determination of enzymatic activity, the high performance liquid chromatography (HPLC) for the determination of phenol concentration after oxidation, and a colorimetric method making use of solutions of borate buffer, 4-aminoantipyrine and potassium ferricyanide as well as reading of the absorbance at 546nm to investigate phenol biosorption, while the presence of polyphenols in "vegetation water" was determined by the Folin-Ciocalteu method. The presence of the tyrosinase in potato varieties Agata and Galette di Bologna was shown to be very low, thus suggesting to change the biosorbent material. So, additional tests were done on apples, kiwi, banana and mushroom, but only the last showed a considerable activity...

Activity of enzymes associated with the enzymatic browning of minimally processed potatoes

The purpose of the present study was to evaluate the effect of different potato cultivars and storage temperatures on the specific activity of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) in minimally processed potatoes. Potato cultivars Agata, Asterix and Monalisa were selected, washed, peeled, diced, sanitized, centrifuged, vacuum- packed and stored at 5 and 15°C for 9 and 5 days, respectively. There was an increase in the enzymatic activity in all the cultivars stored at 15°C. The cultivars 'Agata' and 'Asterix' stored at 5ºC did not differ significantly between them for the PAL, PPO and POD activities. The PAL, PPO and POD activities were also influenced by the storage temperature. The cultivars Agata and Asterix were more suitable in minimal processing than 'Monalisa', which was more susceptible to oxidative browning.

Biochemical Defense against Die-Back Disease of a Traditional Medicinal Plant Mimusops elengi Linn.

Mimusops elengi (Linn.) commonly known as Bakul is one such tree native to the Western Ghat region of the peninsular India. However, today this tree is also found growing in other parts of the tropical and sub tropical regions of the world. The stem, barks, leaves and fruits are used in various Ayurvedic and folk medications to treat various ailments. Die-back disease caused by Alternaria lunata severely affects the plants grown in and around Burdwan, West Bengal, India. An investigation was carried out to study the phenolics along with their oxidizing enzymes that involve in defense against the activity of the pathogen. Peroxidase activity reached its peak on 14th day after infection whereas polyphenol oxidase mediated phenol oxidation was increased upto 21st day in the infected tissues. The enhancement of phenols and their oxidizing enzymes in infected plants affords resistance of the host against die-back

Analysis on three isozymes in plants of Curcuma L / 中草药

Objective: To explore the interspecific and intraspecific genetic relationships of six species in Curcuma L. Methods: The superoxide dismutase (SOD), polyphenol oxidase (PPO), and cytochrome-oxidase (COD) were studied by vertical slab Polyacrylamide gel electrophoresis (PAGE). The three isozymes data were analysed by using clustering method UPGMA. Results: The six species in Curcuma L. can largely be distinguished by zymogram of three isozymes; Moreover, PPO and COD can be used to distinguish the different accessions in the same species of Curcuma L. Conclusion: The genetic relationships among different accessions are related with the geographical origin. Clustering approach could make a distinction between Curcuma longa and C. sichuanensis. The differentiation has happened between the wild and cultivated species of Curcuma L.

Study on browning mechanism of drying Pinelliae Rhizoma / 中草药

Objective: To study the browning mechanism of drying Pinelliae Rhizoma. Methods: The activity of polyphenol oxidase (PPO) was detected by ultraviolet spectrophotometry, and the surface color data of drying Pinelliae Rhizoma were measured by chromaticity instrument. To draw a conclusion that whether Enzymatic browning was the unique factor of browning reaction or not by analyzing the relationship between the above two sets of data. To detect the kinds and content of reducing sugar by HPLC-ELSD and measure the kinds of amino acids in Pinelliae Rhizoma by amino acid analyzer. Through testing the results the possibility of Maillard reaction was analyzed. Results: The factor of the color-change of Pinelliae Rhizoma is not unique, Enzymatic browning is in the prophase of the drying process and Maillard reaction also contributes to the color-change. Conclusion: The factor in the process of Pinelliae Rhizoma color-change is not single. Both enzymatic browning and Maillard reaction impact on the color-change of Pinelliae Rhizoma.

Embalagens e recobrimento em lichias (Litchi chinensis Sonn.) armazenadas sob condições não controladas / Packing and covering in lychee (Litchi chinensis Sonn.) stored under uncontrolled conditions

A lichia (Litchi chinensis Sonn.) é um fruto subtropical de alto potencial comercial devido ao seu sabor levemente acidificado, excelente aroma, alto valor nutritivo e atrativa cor vermelha da casca. Ainda no campo, a cor da casca altera-se facilmente, tornando-se escurecida em resposta a estresses (alterações da umidade relativa e ataque de patógenos). Após colhida, a casca da lichia perde rapidamente sua cor vermelha. O escurecimento da casca tem sido atribuído a rápida degradação da antocianina, assim como: à rápida perda de umidade pelo fruto e à atividade de enzimas oxidativas como polifenoloxidases e peroxidases. Dada essa alta perecibilidade, o controle do escurecimento é fundamental para o aumento na vida útil pós-colheita, visando ao mercado interno e à exportação de frutas. Avaliou-se, neste trabalho, o comportamento pós-colheita de lichias da cv. Bengal quanto ao escurecimento da casca e às modificações relacionadas com a qualidade da polpa de lichias submetidas a diferentes embalagens: bandeja recoberta com filme de polietileno de baixa densidade com e sem perfurações e frutos recobertos com película de fécula de mandioca (3 por cento). Os frutos foram mantidos em temperatura ambiente (25,1ºC±1,5ºC; 69,3 por cento±8,62 por centoUR) e armazenados por seis dias. Foram realizadas análises físicas, químicas e bioquímicas no dia 0 e a cada 2 dias, até osexto dia de armazenamento. A embalagem recoberta com filme de polietileno perfurado apresentou-se eficiente na redução da perda de massa, escurecimento da casca e na manutenção do teor de antocianina da casca de lichias durante seis dias de armazenamento, em temperatura ambiente.

Lychee is a subtropical fruit of high commercial value, due to its slightly acid taste, excellent aroma, high nutritive value and attractive deep bright red color of its peel. Also in the field, skin color changes easily, becoming dark in response to stress (changes in relative humidity and the incidence of pathogens). Harvested lychee fruit rapidly loses its bright red skin colour. Peel browning of harvested lychee has largely been attributed to the rapid degradation of the anthocyanin pigments as well as the rapid loss of moisture from the fruit and the activity of oxidative enzymes such polyphenoloxidase and peroxidases. Due to it high perishability, browning control is a fundamental process to the increase of post-harvest useful life aiming the home market and fruit exportation. This study evaluated the postharvest behavior of Litchi cv. Bengal fruits regarding pericarp browning and changes on lychee fruits pulp quality when different packing is applied: plastic trays covered with parafilm or solely parafilm, and fruits covered with cassava starch film (3 percent). Lychee fruits were stored for six days at room temperature (25.1ºC±1.5; 69.3 percentUR). Physical, chemical and biochemical analyses were performed on day 0 and on every two days till the end of the storage period. The package covered with perforated polyethylene film was efficient in reducing weight loss, skin browning and maintenance of the anthocyanin content of the bark of leeches for six days of storage at room temperature.

Caracterização cinética da enzima catecolase (Polifenol oxidase) em extratos brutos da polpa e da casca de berinjela (Solanum melongena L.) / Kinetic characterization of enzyme catecolase (Polyphenol oxidase) in crude extracts of the pulp and peel of eggplant (Solanum melongena L.)

Objetivo - Foi analisado como material biológico os extratos brutos da polpa e da casca de berinjela (Solanum melongena L.), que é fonte da enzima Polifenol oxidase (PFO) [EC.1.14.18.1] e estes foram estudados como materiais biocatalíticos para a oxidação aeróbica de substratos fenólicos19. Métodos - Extraiu-se a PFO dos extratos por trituração, filtração e centrifugação. Através da medida de absorbância e método do Biureto, obteve-se a atividade e a proteína total. Quantidade e tempo de contato do polímero foram determinados espectrofotometricamente. A caracterização cinética da PFO baseou-se na temperatura ótima, estabilidade ao calor, pH ótimo de atividade e de estabilidade. Os valores obtidos foram comparados com os da polpa e casca de banana nanica. Resultados - A atividade específica da PFO na banana nanica (1056 u/mg da polpa e 1537,5 u/mg da casca) é superior à do extrato de berinjela (376,5 u/mg da polpa e 500 u/mgda casca). Os valores de pH de atividade (pH 5,0) e de estabilidade (pH 7,0), tempo de contato com o polímero (zero) e de armazenamento (34 dias) foram iguais para ambos os extratos. A atividade da PFO foi superior na casca quando comparada a polpa de berinjela. A massa de polímero PVP necessária para adsorção de compostos polifenólicos excedentes foi três vezes maior na polpa do que na casca. A temperatura ótima de atividade para a polpa foi de 40°C e para a casca de 15°C. Conclusões - A caracterização da PFO da berinjela é similar a da banana nanica, porém, a maior atividade específica desta última a torna mais propícia na construção do biossensor para quantificar fenóis/polifenóis em amostras.

Objective - Biological material was analyzed as the crude extracts of the pulp and peel of eggplant (Solanum melongena L.), which is the source of the enzyme Polyphenol oxidase (PPO) [EC.1.14.18.1] and these have been studied as materials for the biocatalytic aerobic oxidation of phenolic substrates19. Methods - Drew to PPO extracts by grinding, filtering and centrifuging. By measuring the absorbance and the Biuret method, we obtained activity and total protein. Amount and contact time of the polymer were determined spectrophotometrically. The kinetic characterization of PPO was based on the study of the optimum temperature, heat stability, pH optimum of activity and stability. The values obtained were compared with those of banana pulp nanica. Results - Results showed that the specific activity of PPO in the banana nanica (1056 u/mg of pulp and 1537.5 u/mg of peel) is higher than in the extract of eggplant (376.5u/mg of pulp and 500 u/mg of peel). The pH values of activity (pH 5.0) and stability (pH 7.0), time of contact with the polymer (zero) and storage (34 days) were similar for both extracts. The activity of PPO was higher in peel compared to the eggplant pulp. The mass of polymer PVP required for adsorption of polyphenolics compounds was three times higher in the pulp than in peel. The optimum temperature for activity of the pulp was 40°C and the peel of 15°C. Conclusions - The characterization of PPO eggplant is similar to the banana, however, the highest specific activity that makes it more conducive to the construction of biosensor to quantify phenols / polyphenols in the samples.