Photo-Cross-Linked Self-Assembled Poly(ethylene oxide)-Based Hydrogels Containing Hybrid Junctions with Dynamic and Permanent Cross-Links

Homogeneous hydrogels were formed by self-assembly of triblock copolymers via association of small hydrophobic end blocks into micelles bridged by large poly­(ethylene oxide) central blocks. A fraction of the end blocks were photo-cross-linkable and could be rapidly cross-linked covalently by in situ UV irradiation. In this manner networks were formed with well-defined chain lengths between homogeneously distributed hybrid micelles that contained both permanent and dynamically cross-linked end blocks. Linear rheology showed a single relaxation mode before in situ irradiation intermediate between those of the individual networks. The presence of transient cross-links decreased the percolation threshold of the network rendered permanent by irradiation and caused a strong increase of the elastic modulus at lower polymer concentrations. Large amplitude oscillation and tensile tests showed significant increase of the fracture strain caused by the dynamic cross-links

Transformation of pZLY2 into <i>Saccharomyces cerevisiae</i> W5 and detection of the dominant selective marker (blasticidin resistance) and reporter gene (<i>gus</i> gene).

<p>A. 1: No colonies grow on YEPD solid medium with blasticidin when <i>Saccharomyces cerevisiae</i> W5 was not transformed by pZLY2; 2 and 3: several colonies grow on YEPD solid medium with blasticidin when <i>Saccharomyces cerevisiae</i> W5 was transformed by pZLY2. B. <i>Saccharomyces cerevisiae</i> W5 cells observed under light microscopy (1600×). C GUS-stained <i>Saccharomyces cerevisiae</i> W5 cells, as observed by light microscopy (1600×). D. Positive transformants of <i>Saccharomyces cerevisiae</i> W5 observed by light microscopy (1600×). No morphological differences can be seen between the cells. E. GUS-stained transformants of <i>Saccharomyces cerevisiae</i> W5, as observed by light microscopy (1600×), showing the blue cells.</p

Fermentation of glucose as the sole carbon source by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.

<p>Data are expressed as the mean values ± standard deviation of at least three independent experiments. The different letters in the same column of the data indicated in the p<0.05 level of significant difference.</p><p>Fermentation of glucose as the sole carbon source by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.</p

Screening of protoplast fusants.

<p>A. Many colonies are found to grow on YEPDS regenerated solid medium when protoplast fusants are spread on it. B and C. Several colonies grow on YEPDS regenerated solid medium with blasticidin and G418.</p

Transformation of pZLY1 into <i>Candida shehatae</i> 20335 and detection of the dominant selective marker (G418 resistance) and reporter genes (GFP gene).

<p>A. 1: Colonies were not observed on YEPX solid medium with G418 when <i>Candida shehatae</i> 20335 was not transformed by pZLY1; 2: several colonies grew on YEPX solid medium with G418 when <i>Candida shehatae</i> 20335 was transformed by pZLY1. B. <i>Candida shehatae</i> 20335 cells were observed under light microscopy (1600×). C. <i>Candida shehatae</i> 20335 transformants were observed under light microscopy (1600×). No morphological differences can be seen between the cells. D. <i>Candida shehatae</i> 20335 cells observed under fluorescence microscopy (1000×), showing GFP is not expressed in untransformed cells. E. <i>Candida shehatae</i> 20335 cells observed under fluorescence microscopy (1000×), showing GFP is expressed in transformants.</p

XR, XDH and XKS activities in different cell extracts (48 h).

<p>XR, XDH and XKS activities in different cell extracts (48 h).</p

Fermentation of xylose as the sole carbon source by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.

<p>Data are expressed as the mean values ± standard deviation of at least three independent experiments. The different letters in the same column of the data indicated in the p<0.05 level of significant difference.</p><p>Fermentation of xylose as the sole carbon source by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.</p

Changes in the concentrations of residual glucose (black circle), residual xylose (open circle), ethanol production (black square), xylitol production (open square), cell dry weight (open rhombus), qglu (black triangle) and qxyl (open triangle) in the presence of <i>Saccharomyces cerevisiae</i> W5 (a), <i>Candida shehatae</i> 20335 (b) and ZLYRHZ7 (c) during fermentation in the presence of both glucose and xylose as carbon sources.

<p>Data are expressed as the mean ± standard deviation of three independent experiments.</p

The amplified genes of xyl1, xyl2 and XKS using the chromosomes of ZLYRHZ7 and <i>S. cerevisiae</i> W5 as the template.

<p>M is the marker; lanes 1, 3 and 5 are the amplified genes of xyl1, xyl2 and XKS of <i>S. cerevisiae</i> W5; lanes 2, 4 and 6 are the amplified genes of xyl1, xyl2 and XKS of ZLYRHZ7.</p

Fermentation of glucose–xylose by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.

<p>Data are expressed as the mean values ± standard deviation of at least three independent experiments. The different letters in the same column of the data indicate the level of significant differences at p<0.05.</p><p>Fermentation of glucose–xylose by <i>Candida shehatae</i> 20335, <i>Saccharomyces cerevisiae</i> W5 and ZLYRHZ7 transformants.</p