Coating quality as affected by core particle segregation in fluidized bed processing

[EN] Fluidized bed coating is an important technique in the food powder industry, where often particles of a wide size distribution are dealt with. In this paper, glass beads of different particle size distribution were coated with sodium caseinate in a top-spray fluid bed unit. Positron Emission Particle Tracking (PEPT) was used to visualize and quantify the particle motion in the fluidized bed. Confocal Laser Scanning Microscopy combined with image analysis were used to investigate the effect of core particle size and its distribution on the thickness and quality of the coating. Particle size significantly affected the thickness and quality of the coating, due to differences in the corresponding fluidization patterns, as corroborated by PEPT observations. As the particle size distribution becomes narrower, segregation is less likely to occur. This results in a thicker coating which is, however, less uniform compared to when cores of a wider particle size distribution are spray coated. (C) 2012 Elsevier Ltd. All rights reserved.The authors wish to thank the financial support received from the Fund for Scientific Research-Flanders (Belgium) (F.W.O.-Vlaanderen), as well as from the Programa de Apoyo a la Investigacion y Desarrollo from the Universitat Politecnica de Valencia.Atarés Huerta, LM.; Depypere, F.; Pieters, J.; Dewettinck, K. (2012). Coating quality as affected by core particle segregation in fluidized bed processing. Journal of Food Engineering. 113(3):415-421. doi:10.1016/j.jfoodeng.2012.06.012S415421113

Chloroplast ribosomal intron of Chlamydomonas reinhardtii: in vitro self-splicing, DNA endonuclease activity and in vivo mobility.

All chloroplast 23S ribosomal RNA genes of the unicellular alga Chlamydomonas reinhardtii contain an 888 bp group I intron with an internal open reading frame (ORF). A precursor RNA encompassing the intron with its 5' and 3' flanking sequences was shown to self-splice both during in vitro transcription and upon incubation of the isolated pre-RNA under self-splicing conditions. Expression of the internal ORF in Escherichia coli in the presence of a plasmid containing a cDNA corresponding to the intronless form of the 23S rRNA gene resulted in specific cleavage of the cDNA at or close to the exon junction sequence. To test whether this ORF-encoded double-strand DNA endonuclease is involved in intron mobility in vivo, the same ribosomal cDNA was stably integrated into the C. reinhardtii chloroplast genome using particle gun mediated transformation. All the transformants with the cDNA integrated at the expected site in the chloroplast genome had the intron precisely inserted at the artificial exon junction site. These experiments demonstrate that the chloroplast ribosomal intron of C. reinhardtii behaves as a ribozyme in vitro and also as a mobile genetic element in vivo provided a target site is present

Double Strand Break-Induced Recombination in Chlamydomonas Reinhardtii Chloroplasts

The mechanisms of chloroplast recombination are largely unknown. Using the chloroplast-encoded homing endonuclease I-CreI from Chlamydomonas reinhardtii, an experimental system is described that allows the study of double strand break (DSB)-induced recombination in chloroplasts. The I-CreI endonuclease is encoded by the chloroplast ribosomal group I intron of C.reinhardtiiand cleaves specifically intronless copies of the large ribosomal RNA (23S) gene. To study DSB-induced recombination in chloroplast DNA, the genes encoding the I-CreI endonuclease were deleted and a target site for I-CreI, embedded in a cDNA of the 23S gene, was integrated at an ectopic location. Endonuclease function was transiently provided by mating the strains containing the recombination substrate to a wild-type strain. The outcome of DSB repair was analyzed in haploid progeny of these crosses. Interestingly, resolution of DSB repair strictly depended upon the relative orientation of the ectopic ribosomal cDNA and the adjacent copy of the 23S gene. Gene conversion was observed when the 23S cDNA and the neighbouring copy of the 23S gene were in opposite orientation, leading to mobilization of the intron to the 23S cDNA. In contrast, arrangement of the 23S cDNA in direct repeat orientation relative to the proximal 23S gene resulted in a deletion between the 23S cDNA and the 23S gene. These results demonstrate that C.reinhardtii chloroplasts have an efficient system for DSB repair and that homologous recombination is strongly stimulated by DSBs in chloroplast DN