Stereospecific Microbial Conversion of Lactic Acid into 1,2‑Propanediol

Biocatalytic syntheses are increasingly explored as the alternate platform of chemical production in order to address the sustainable development challenge faced by the current chemical industry. Here, we report the design and implementation of an artificial pathway to convert lactic acid into 1,2-propanediol. It circumvents a highly cytotoxic intermediate that exists in a widely used natural pathway. We identified and characterized a key enzyme that catalyzed the nonnatural step of the pathway. After 72 h of cultivation under shake-flask conditions, an <i>Escherichia coli</i> biocatalyst expressing the artificial route synthesized 1.5 g/L of <i>R</i>- or 1.7 g/L of <i>S</i>-1,2-propanediol from d- or l- lactic acid at high enantiomeric purity, respectively. The bioconversion is part of a novel biosynthetic pathway that can be further incorporated into appropriate microbial hosts for the <i>de novo</i> synthesis of optically pure 1,2-propanediol from renewable feedstocks

Numerical results of <i>d</i>_<i>T</i>/<i>d</i>_<i>p</i>.

(a) T(1) case; (b) T(2) case; (c) T(3) case. The theoretical error bounds are shown as dash-dotted lines.</p

Comparasion of different (1 + <i>ε</i>) − <i>approximation</i> algorithms to compute the diameter of <i>T</i>.

Comparasion of different (1 + ε) − approximation algorithms to compute the diameter of T.</p

Percentage inhibition of MDA proliferation by proso millet extract.

<p>MDA cell (2.5×10⁴/mL) were incubated for 6 h to allow sufficient attachment. For the lower level treatment, the initial concentration for samples was 30 mg DW h to allow sufficient attachment. For the lower level treatment, the initial concentration for samples was 30 mg DW mg DW/mL, whereas the high concentration was 180 mg DW mg DW/mL. After 72 h of incubation, cell proliferation was determined by the methylene blue assay from the absorbance at 570 nm for each concentration compared to the control. Data were reported as mean h of incubation, cell proliferation was determined by the methylene blue assay from the absorbance at 570 nm for each concentration compared to the control. Data were reported as mean nm for each concentration compared to the control. Data were reported as mean ± SD for three replications.</p

Diagram of the partition for the point set.

Solid points are real points in the set T, while empty points are virtual points in the set of pis.</p

PSC antioxidant activity of proso millet.

<p>Peroxyl radical scavenging capacity assay is based on the degree of inhabitation of dichlorofluorescin oxidation by antioxidants that scavenge peroxyl radicals, generated from thermal degradation of 2, 2′azobis (amidinopropane). The median effective concentration (EC₅₀) was defined as the dose required to cause a 50% inhibition for each sample extract. Results obtained for sample extract antioxidant activities were expressed as micromoles of vitamin C equivalents/100 g DW. Analyses were conducted in triplicate, with mean values shown and standard deviation depicted by the vertical bars. Column marked by the same letter are not significantly different from each other g DW. Analyses were conducted in triplicate, with mean values shown and standard deviation depicted by the vertical bars. Column marked by the same letter are not significantly different from each other (<i>p</i><0.05).</p

Evolution of Src Homology 2 (SH2) Domain to Recognize Sulfotyrosine

Protein tyrosine O-sulfation is considered as the most common type of post-translational tyrosine modification in nature and plays important roles in extracellular biomolecular interactions. To facilitate the mapping, biological study, and medicinal application of this type of post-translational modification, we seek to evolve a small protein scaffold that recognizes sulfotyrosine with high affinity. We focused our efforts on the engineering of the Src Homology 2 (SH2) domain, which represents the largest class of known phosphotyrosine-recognition domain in nature and has a highly evolvable binding pocket. By using phage display, we successfully engineered the SH2 domain to recognize sulfotyrosine with high affinity. The best mutant, SH2-60.1, displayed more than 1700 fold higher sulfotyrosine-binding affinity than that of the wild-type SH2 domain. We also demonstrated that the evolved SH2 domain mutants could be used to detect sulfoprotein levels on the cell surface. These evolved SH2 domain mutants can be potentially applied to the study of protein tyrosine O-sulfation with proper experimental designs

Antiproliferative activities of proso millet against MAD human breast cancer.

<p>The antiproliferative activities of proso millets against MAD cells are expressed as the median effective dose (EC₅₀). Values are based on triplicate tests, with mean values shown and standard deviation depicted by the vertical bars. Column marked by the same letter are not significantly different from each other (<i>p</i><0.05).</p

Phenolic contents of proso millet.

<p>TPCs were quantified using the Folin-Ciocalteu reagent with gallic acid as the standard. Absorbance was read at 760 nm after 90 min of reaction. Results are expressed as mg gallic acid equivalnts nm after 90 min of reaction. Results are expressed as mg gallic acid equivalnts min of reaction. Results are expressed as mg gallic acid equivalnts/100 g DW. Analyses were conducted in triplicate, with mean values shown and standard deviation depicted by the vertical bars. Column marked by the same letter are not significantly different from each other g DW. Analyses were conducted in triplicate, with mean values shown and standard deviation depicted by the vertical bars. Column marked by the same letter are not significantly different from each other (<i>p</i><0.05).</p

Description of proso millet samples.

<p>Description of proso millet samples.</p