Influence of Compounding Parameters on Color Space and Properties of Thermoplastics with Ultramarine Blue Pigment.

The incorporation of thermoplastics with pigments imparts diverse aesthetic qualities and properties to colored thermoplastic products. The selection of pigment type and content, along with specific processing conditions, plays a pivotal role in influencing color properties and overall product performance. This study focuses on optimizing these parameters to ensure the desired color quality and product functionality. Two types of polypropylene copolymer (PPCP) with different melt flow rates (MFRs) and acrylonitrile butadiene styrene (ABS) were compounded with ultramarine blue pigment masterbatch (MB) in concentrations ranging from 1 to 5 wt.% using a twin-screw extruder. The compounding process was conducted at a constant screw speed of 200 rpm and a die temperature of 210 °C. The effects of screw speed and die temperature were investigated at a constant MB of 3 wt.%. Colored samples were fabricated by injection molding. Microscopic analysis revealed a well-dispersed pigment within the PPCP matrix when using the MB. Rheological properties, assessed through the power law index, confirmed effective pigment dispersion, facilitated by shear thinning behavior and controlled shear rate via the manipulation of screw speed and die temperature. The effects of masterbatch contents and processing conditions on color spaces were evaluated using CIELAB and CIELCH, with one-way ANOVA employed to identify statistical significance. Higher opacity in high-MFR PPCP and ABS resulted in increased lightness and color strength, surpassing low-MFR PPCP by 15-40% at equivalent MB contents. Masterbatch content emerged as a significant factor influencing the color spaces of all colored thermoplastics. Further analysis, including Fisher pairwise comparisons of one-way ANOVA, revealed that screw speed influenced the redness and hue of low-MFR PPCP, whereas die temperature affected the lightness and hue of high-MFR PPCP and ABS. Interestingly, the blueness and chroma of colored thermoplastics were minimally affected by both screw speed and die temperature. Notably, regardless of processing conditions, the flexural properties of colored thermoplastics remained comparable to the neat polymer when incorporated with ultramarine blue pigment masterbatch.

Improving the functionality of surface-engineered yeast cells by altering the cell wall morphology of the host strain.

The expression of functional proteins on the cell surface using glycosylphosphatidylinositol (GPI)-anchoring technology is a promising approach for constructing yeast cells with special functions. The functionality of surface-engineered yeast strains strongly depends on the amount of functional proteins displayed on their cell surface. On the other hand, since the yeast cell wall space is finite, heterologous protein carrying capacity of the cell wall is limited. Here, we report the effect of CCW12 and CCW14 knockout, which encode major nonenzymatic GPI-anchored cell wall proteins (GPI-CWPs) involved in the cell wall organization, on the heterologous protein carrying capacity of yeast cell wall. Aspergillus aculeatus ß-glucosidase (BGL) was used as a reporter to evaluate the protein carrying capacity in Saccharomyces cerevisiae. No significant difference in the amount of cell wall-associated BGL and cell-surface BGL activity was observed between CCW12 and CCW14 knockout strains and their control strain. In contrast, in the CCW12 and CCW14 co-knockout strains, the amount of cell wall-associated BGL and its activity were approximately 1.4-fold higher than those of the control strain and CCW12 or CCW14 knockout strains. Electron microscopic observation revealed that the total cell wall thickness of the CCW12 and CCW14 co-knockout strains was increased compared to the parental strain, suggesting a potential increase in heterologous protein carrying capacity of the cell wall. These results indicate that the CCW12 and CCW14 co-knockout strains are a promising host for the construction of highly functional recombinant yeast strains using cell-surface display technology. KEY POINTS: • CCW12 and/or CCW14 of a BGL-displaying S. cerevisiae strain were knocked out. • CCW12 and CCW14 co-disruption improved the display efficiency of BGL. • The thickness of the yeast cell wall was increased upon CCW12 and CCW14 knockout.

Combined Cell Surface Display of ß-d-Glucosidase (BGL), Maltose Transporter (MAL11), and Overexpression of Cytosolic Xylose Reductase (XR) in Saccharomyces cerevisiae Enhance Cellobiose/Xylose Coutilization for Xylitol Bioproduction from Lignocellulosic Biomass.

Xylitol is a highly valuable commodity chemical used extensively in the food and pharmaceutical industries. The production of xylitol from d-xylose involves a costly and polluting catalytic hydrogenation process. Biotechnological production from lignocellulosic biomass by micro-organisms like yeasts is a promising option. In this study, xylitol is produced from lignocellulosic biomass by a recombinant strain of Saccharomyces cerevisiae (S. cerevisiae) (YPH499-SsXR-AaBGL) expressing cytosolic xylose reductase (Scheffersomyces stipitis xylose reductase [SsXR]), along with a ß-d-glucosidase (Aspergillus aculeatus ß-glucosidase 1 [AaBGL]) displayed on the cell surface. The simultaneous cofermentation of cellobiose/xylose by this strain leads to an ≈2.5-fold increase in Yxylitol/xylose (=0.54) compared to the use of a glucose/xylose mixture as a substrate. Further improvement in the xylose uptake by the cell is achieved by a broad evaluation of several homologous and heterologous transporters. Homologous maltose transporter (ScMAL11) shows the best performance in xylose transport and is used to generate the strain YPH499-XR-ScMAL11-BGL with a significantly improved xylitol production capacity from cellobiose/xylose coutilization. This report constitutes a promising proof of concept to further scale up the biorefinery industrial production of xylitol from lignocellulose by combining cell surface and metabolic engineering in S. cerevisiae.