An enzyme cascade synthesis of ε-caprolactone and its oligomers.

Poly-ε-caprolactone (PCL) is chemically produced on an industrial scale in spite of the need for hazardous peracetic acid as an oxidation reagent. Although Baeyer-Villiger monooxygenases (BVMO) in principle enable the enzymatic synthesis of ε-caprolactone (ε-CL) directly from cyclohexanone with molecular oxygen, current systems suffer from low productivity and are subject to substrate and product inhibition. The major limitations for such a biocatalytic route to produce this bulk chemical were overcome by combining an alcohol dehydrogenase with a BVMO to enable the efficient oxidation of cyclohexanol to ε-CL. Key to success was a subsequent direct ring-opening oligomerization of in situ formed ε-CL in the aqueous phase by using lipase A from Candida antarctica, thus efficiently solving the product inhibition problem and leading to the formation of oligo-ε-CL at more than 20 g L(-1) when starting from 200 mM cyclohexanol. This oligomer is easily chemically polymerized to PCL.

Understanding the evaluation of mHealth app features based on a cross-country Kano analysis.

While mobile health (mHealth) apps play an increasingly important role in digitalized health care, little is known regarding the effects of specific mHealth app features on user satisfaction across different healthcare system contexts. Using personal health record (PHR) apps as an example, this study identifies how potential users in Germany and Denmark evaluate a set of 26 app features, and whether evaluation differences can be explained by the differences in four pertinent user characteristics, namely privacy concerns, mHealth literacy, mHealth self-efficacy, and adult playfulness. Based on survey data from both countries, we employed the Kano method to evaluate PHR features and applied a quartile-based sample-split approach to understand the underlying relationships between user characteristics and their perceptions of features. Our results not only reveal significant differences in 14 of the features between Germans and Danes, they also demonstrate which of the user characteristics best explain each of these differences. Our two key contributions are, first, to explain the evaluation of specific PHR app features on user satisfaction in two different healthcare contexts and, second, to demonstrate how to extend the Kano method in terms of explaining subgroup differences through user characteristic antecedents. The implications for app providers and policymakers are discussed.

Whole-cell double oxidation of n-heptane.

Biocascades allow one-pot synthesis of chemical building blocks omitting purification of reaction intermediates and expenses for downstream processing. Here we show the first whole cell double oxidation of n-heptane to produce chiral alcohols and heptanones. The concept of an artificial operon for co-expression of a monooxygenase from Bacillus megaterium (P450 BM3) and an alcohol dehydrogenase (RE-ADH) from Rhodococcus erythropolis is reported and compared to the widely used two-plasmid or Duet-vector expression systems. Both catalysts are co-expressed on a polycistronic constructs (single mRNA) that reduces recombinant DNA content and metabolic burden for the host cell, therefore increasing growth rate and expression level. Using the artificial operon system, the expression of P450 BM3 reached 81mgg(-1) cell dry weight. In addition, in situ cofactor regeneration through the P450 BM3/RE-ADH couple was enhanced by coupling to glucose oxidation by E. coli. Under optimized reaction conditions the artificial operon system displayed a product formation of 656mgL(-1) (5.7mM) of reaction products (heptanols+heptanones), which is 3-fold higher than the previously reported values for an in vitro oxidation cascade. In conjunction with the high product concentrations it was possible to obtain ee values of >99% for (S)-3-heptanol. Coexpression of a third alcohol dehydrogenase from Lactobacillus brevis (Lb-ADH) in the same host yielded complete oxidation of all heptanol isomers. Introduction of a second ADH enabled further to utilize both cofactors in the host cell (NADH and NADPH) which illustrates the simplicity and modular character of the whole cell oxidation concept employing an artificial operon system.