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Lysine decarboxylases (LDCs) from Escherichia coli, Lactobacillus saerimneri, Streptomyces coelicolor, Selemonas ruminantium, Hafnia alvei, and Vibrio vulnificus were examined for their ability to ...

Sebacic acid (SA) is an aliphatic ten-carbon dicarboxylic acid (1,10-decanedioic acid) with a variety of industrial applications, including the production of plasticizers, lubricants, cosmetics, and plastics. Currently, SA is produced exclusively from alkaline pyrolysis of castor oil. Herein, we present an environmentally friendly green route of SA production from plant oil-derived sources by microbial ω-oxidation. We genetically engineered β-oxidation-blocked diploid yeast Candida tropicalis, and created an effective microbial cell factory with an increase of 46% in SA production by overexpression of genes involved in ω-oxidation of hydrocarbons compared to the original strain. A biotransformation process of SA production from decanoic acid methyl ester was developed to overcome the challenges of high-density cell culture, substrate feed, substrate/intermediate toxicity, and foam generation. Fed-batch production of engineered C. tropicalis resulted in a molar yield of above 98%, a productivity of 0.57 g L−1 h−1, and a final titre of 98.3 g L−1 in a 5-litre fermenter and the results were successfully reproduced using a larger scale 50-litre fermenter. The produced SAs were successfully purified to >99.8% using acid precipitation and recrystallization. Finally, bio-nylon 610 was successfully synthesized by polymerization of the purified SA with hexamethylenediamine and showed thermal properties very similar to those of commercially available nylon 610. The processes developed and described in this study can be employed to produce and isolate SA for the synthesis of bio-nylons, using environmentally friendly procedures based on microbial biotransformation with potential industrial applications.

Fermentative production of cadaverine from renewable resources may support a sustainable biorefinery process to produce carbon-neutral nylons such as biopolyamide 510 (PA510). Cost-competitive prod...

Cadaverine is a C5 diamine monomer used for the production of bio-based polyamide 510. Cadaverine is produced by the decarboxylation of l-lysine using a lysine decarboxylase (LDC). In this study, we developed recombinant Escherichia coli strains for the expression of LDC from Hafnia alvei. The resulting recombinant XBHaLDC strain was used as a whole cell biocatalyst for the high-level bioconversion of l-lysine into cadaverine without the supplementation of isopropyl &beta, d-1-thiogalactopyranoside (IPTG) for the induction of protein expression and pyridoxal phosphate (PLP), a key cofactor for an LDC reaction. The comparison of results from enzyme characterization of E. coli and H. alvei LDC revealed that H. alvei LDC exhibited greater bioconversion ability than E. coli LDC due to higher levels of protein expression in all cellular fractions and a higher specific activity at 37 &deg, C (1825 U/mg protein &gt, 1003 U/mg protein). The recombinant XBHaLDC and XBEcLDC strains were constructed for the high-level production of cadaverine. Recombinant XBHaLDC produced a 1.3-fold higher titer of cadaverine (6.1 g/L) than the XBEcLDC strain (4.8 g/L) from 10 g/L of l-lysine. Furthermore, XBHaLDC, concentrated to an optical density (OD600) of 50, efficiently produced 136 g/L of cadaverine from 200 g/L of l-lysine (97% molar yield) via an IPTG- and PLP-free whole cell bioconversion reaction. Cadaverine synthesized via a whole cell biocatalyst reaction using XBHaLDC was purified to polymer grade, and purified cadaverine was successfully used for the synthesis of polyamide 510. In conclusion, an IPTG- and PLP-free whole cell bioconversion process of l-lysine into cadaverine, using recombinant XBHaLDC, was successfully utilized for the production of bio-based polyamide 510, which has physical and thermal properties similar to polyamide 510 synthesized from chemical-grade cadaverine.

Cadaverine is a C5 diamine monomer used for the production of bio-based polyamide 510. Cadaverine is produced by the decarboxylation of l-lysine using a lysine decarboxylase (LDC). In this study, we developed recombinant Escherichia coli strains for the expression of LDC from Hafnia alvei. The resulting recombinant XBHaLDC strain was used as a whole cell biocatalyst for the high-level bioconversion of l-lysine into cadaverine without the supplementation of isopropyl β-d-1-thiogalactopyranoside (IPTG) for the induction of protein expression and pyridoxal phosphate (PLP), a key cofactor for an LDC reaction. The comparison of results from enzyme characterization of E. coli and H. alvei LDC revealed that H. alvei LDC exhibited greater bioconversion ability than E. coli LDC due to higher levels of protein expression in all cellular fractions and a higher specific activity at 37 °C (1825 U/mg protein > 1003 U/mg protein). The recombinant XBHaLDC and XBEcLDC strains were constructed for the high-level production of cadaverine. Recombinant XBHaLDC produced a 1.3-fold higher titer of cadaverine (6.1 g/L) than the XBEcLDC strain (4.8 g/L) from 10 g/L of l-lysine. Furthermore, XBHaLDC, concentrated to an optical density (OD600) of 50, efficiently produced 136 g/L of cadaverine from 200 g/L of l-lysine (97% molar yield) via an IPTG- and PLP-free whole cell bioconversion reaction. Cadaverine synthesized via a whole cell biocatalyst reaction using XBHaLDC was purified to polymer grade, and purified cadaverine was successfully used for the synthesis of polyamide 510. In conclusion, an IPTG- and PLP-free whole cell bioconversion process of l-lysine into cadaverine, using recombinant XBHaLDC, was successfully utilized for the production of bio-based polyamide 510, which has physical and thermal properties similar to polyamide 510 synthesized from chemical-grade cadaverine.

Structural changes of and the interactions between organic materials in liquid crystal display panel after UV exposure were systematically investigated using FT-IR, XPS, AFM, and LC-ESI-MS. When the photo-curing of the sealant was imperfect during the assembly of LCD panel, both the components in the sealant such as UV-initiator contaminated the LC's and the stray UV light oxidized the benzene rings and other chemical bonds in the polymer backbone of the alignment layer. This resulting contamination of LC's and degradation of the alignment layer could disturb the pretilt angle of the VA-mode LC's and cause the display defects on the LCD panel. In this regard, careful control of the photo-curing of the sealant will be required for precise alignment of the LCD panel and better performance of the display.

Aromatic polyimide thin films are used as the alignment film in thin film transistor-liquid crystal displays (TFT-LCD's). The films play an important role in the initial alignment of the liquid crystal materials in LCD panels. Therefore, any structural or morphological deformation may lead to defect in the physical interactions thus malfunction of the display eventually. for example, an LCD is known to bear image sticking problem when it is assembled following 3 days or longer stagnancy in the process after main curing of the layer. In this paper, the molecular orientation of polyimide surfaces with respect to the stagnancy is investigated by means of surface sensitive Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. NEXAFS measurements clearly reveal preferred in-plane and out-of-plane orientation of phenyl and C=O groups at the surface of the polyimide thin film in regard to the stagnancy after main curing. with longer stagnancy phenyl and C=O groups preferred in-plane orientation. The preferred in-plane orientation within the film can accelerate the image sticking problem in LCD's operating in PVA mode. Based on the result, vertical alignment of polyimide pendant group is found helpful for the better alignment of LC molecules in LCD's operating in the patterned vertical alignment (PVA) mode.