Home About us Contact
|
Home About us Contact | ||
|
|
||
Wall Degrading Enzymes (wall + degrading_enzyme)
Kinds of Wall Degrading Enzymes Selected AbstractsEffect of Cell Wall Degrading Enzymes on In Vitro Carotene Accessibility in Lactic Acid Fermented Carrot BeverageJOURNAL OF FOOD SCIENCE, Issue 2 2004V. Díaz ABSTRACT: Carrot purées with different particle size were prepared from fresh carrots using 2 different food processors. The purées were fermented with lactic acid bacteria (Lactobacillus plantarum) with and without addition of cell wall degrading enzymes (Pectinex® Ultra SP-L and CellubrixTM L). The bioaccessibility of carotenes was estimated using an in vitro digestion method. In carrots processed to a particle size <1.5 mm, the in vitro ,-carotene accessibility was 46% and neither fermentation nor addition of cell wall-degrading enzymes had any further effect on the in vitro accessibility. In carrot purées with a coarser particle size, the in vitro ,-carotene accessibility was 18%; that significantly increased by adding high amounts of cellulases or pectinases or a combination of the enzymes either in low or high amounts. The improved accessibility was correlated with reduced particle size of the carrot purée. [source] Sclerotinia sclerotiorum: When "to be or not to be" a pathogen?FEMS MICROBIOLOGY LETTERS, Issue 2 2005Dwayne D. Hegedus Abstract Sclerotinia sclerotiorum is unusual among necrotrophic pathogens in its requirement for senescent tissues to establish an infection and to complete the life cycle. A model for the infection process has emerged whereby the pathogenic phase is bounded by saprophytic phases; the distinction being that the dead tissues in the latter are generated by the actions of the pathogen. Initial colonization of dead tissue provides nutrients for pathogen establishment and resources to infect healthy plant tissue. The early pathogenicity stage involves production of oxalic acid and the expression of cell wall degrading enzymes, such as specific isoforms of polygalacturonase (SSPG1) and protease (ASPS), at the expanding edge of the lesion. Such activities release small molecules (oligo-galacturonides and peptides) that serve to induce the expression of a second wave of degradative enzymes that collectively bring about the total dissolution of the plant tissue. Oxalic acid and other metabolites and enzymes suppress host defences during the pathogenic phase, while other components initiate host cell death responses leading to the formation of necrotic tissue. The pathogenic phase is followed by a second saprophytic phase, the transition to which is effected by declining cAMP levels as glucose becomes available and further hydrolytic enzyme synthesis is repressed. Low cAMP levels and an acidic environment generated by the secretion of oxalic acid promote sclerotial development and completion of the life cycle. This review brings together histological, biochemical and molecular information gathered over the past several decades to develop this tri-phasic model for infection. In several instances, studies with Botrytis species are drawn upon for supplemental and supportive evidence for this model. In this process, we attempt to outline how the interplay between glucose levels, cAMP and ambient pH serves to coordinate the transition between these phases and dictate the biochemical and developmental events that define them. [source] A Novel Process for the Recovery of Polyphenols from Grape (Vitis vinifera L.) PomaceJOURNAL OF FOOD SCIENCE, Issue 2 2005Dietmar Kammerer ABSTRACT: A novel process for enzyme-assisted extraction of polyphenols from winery by-products was established on a pilot-plant scale. Optimization of enzymatic hydrolysis of grape skins, that is, selection of pectinolytic and cellulolytic enzymes, enzyme-substrate ratio, and time-temperature regime of enzymatic treatment, was conducted on a laboratory scale. Enzyme activities were monitored by viscosity measurement of resuspended grape pomace and by quantification of oligomeric pectin and cellulose degradation products released from cell wall material. Optimal conditions were obtained with 5000 ppm (based on dry matter) of a pectinolytic and 2500 ppm of a cellulolytic enzyme preparation, respectively, at 50°C, which were also applied in pilot-plant scale experiments. Concomitant determination of individual polyphenolics demonstrated a significantly improved yield for most compounds when compared with experiments without enzyme addition. Recovery rates were comparable to those obtained when grape pomace was extracted using sulfite. Pre-extraction of the pomace with hot water followed by treatment with cell wall degrading enzymes even increased yields of phenolic compounds. Only some quercetin glycosides and malvidin coumaroylglucoside were partly hydrolyzed due to enzyme side activities. This new process may provide a valuable alternative to the application of sulfite, which is considered crucial in food processing. [source] Effect of Cell Wall Degrading Enzymes on In Vitro Carotene Accessibility in Lactic Acid Fermented Carrot BeverageJOURNAL OF FOOD SCIENCE, Issue 2 2004V. Díaz ABSTRACT: Carrot purées with different particle size were prepared from fresh carrots using 2 different food processors. The purées were fermented with lactic acid bacteria (Lactobacillus plantarum) with and without addition of cell wall degrading enzymes (Pectinex® Ultra SP-L and CellubrixTM L). The bioaccessibility of carotenes was estimated using an in vitro digestion method. In carrots processed to a particle size <1.5 mm, the in vitro ,-carotene accessibility was 46% and neither fermentation nor addition of cell wall-degrading enzymes had any further effect on the in vitro accessibility. In carrot purées with a coarser particle size, the in vitro ,-carotene accessibility was 18%; that significantly increased by adding high amounts of cellulases or pectinases or a combination of the enzymes either in low or high amounts. The improved accessibility was correlated with reduced particle size of the carrot purée. [source] Soft rot erwiniae: from genes to genomesMOLECULAR PLANT PATHOLOGY, Issue 1 2003Ian K. Toth SUMMARY The soft rot erwiniae, Erwinia carotovora ssp. atroseptica (Eca), E. carotovora ssp. carotovora (Ecc) and E. chrysanthemi (Ech) are major bacterial pathogens of potato and other crops world-wide. We currently understand much about how these bacteria attack plants and protect themselves against plant defences. However, the processes underlying the establishment of infection, differences in host range and their ability to survive when not causing disease, largely remain a mystery. This review will focus on our current knowledge of pathogenesis in these organisms and discuss how modern genomic approaches, including complete genome sequencing of Eca and Ech, may open the door to a new understanding of the potential subtlety and complexity of soft rot erwiniae and their interactions with plants. Taxonomy: ,The soft rot erwiniae are members of the Enterobacteriaceae, along with other plant pathogens such as Erwinia amylovora and human pathogens such as Escherichia coli, Salmonella spp. and Yersinia spp. Although the genus name Erwinia is most often used to describe the group, an alternative genus name Pectobacterium was recently proposed for the soft rot species. Host range:,Ech mainly affects crops and other plants in tropical and subtropical regions and has a wide host range that includes potato and the important model host African violet ( Saintpaulia ionantha ). Ecc affects crops and other plants in subtropical and temperate regions and has probably the widest host range, which also includes potato. Eca , on the other hand, has a host range limited almost exclusively to potato in temperate regions only. Disease symptoms: ,Soft rot erwiniae cause general tissue maceration, termed soft rot disease, through the production of plant cell wall degrading enzymes. Environmental factors such as temperature, low oxygen concentration and free water play an essential role in disease development. On potato, and possibly other plants, disease symptoms may differ, e.g. blackleg disease is associated more with Eca and Ech than with Ecc. Useful websites: ,http://www.scri.sari.ac.uk/TiPP/Erwinia.htm, http://www.ahabs.wisc.edu:16080/pernalab/erwinia/index.htm, http://www.tigr.org/tdb/mdb/mdbinprogress.html, http://www.sanger.ac.uk/Projects/E_carotovora/. [source] | ||||||||||