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The waterproofing structure used in underground engineering of polypropylene weld seam with groove welding is studied. The purpose of this paper is to explore the computational mathematical relationship between hydraulic load and internal force of plastic weld. Studies have shown that water pressure failure stress σf and theoretical constitutive stress σv have the following relationships: σf · β ≤ σv, where β is the factor of relation coefficient. This conclusion provides the method and idea for the application of polypropylene plastic weld in lining waterproof engineering, and also provides reference data for engineering design. [ABSTRACT FROM AUTHOR]

Organic acids are organic compounds that can be synthesized using biological systems. They often contain one or more low molecular weight acidic groups, such as carboxyl group and sulphonic group. Organic acids are widely used in food, agriculture, medicine, bio-based materials industry and other fields. Yeast has unique advantages of biosafety, strong stress resistance, wide substrate spectrum, convenient genetic transformation, and mature large-scale culture technology. Therefore, it is appealing to produce organic acids by yeast. However, challenges such as low concentration, many by-products and low fermentation efficiency still exist. With the development of yeast metabolic engineering and synthetic biology technology, rapid progress has been made in this field recently. Here we summarize the progress of biosynthesis of 11 organic acids by yeast. These organic acids include bulk carboxylic acids and high-value organic acids that can be produced naturally or heterologously. Finally, future prospects in this field were proposed.

Objective: To study dehydrogenation by short ethoxy chain nonylphenols dehydrogenase (sNPEO-DH) from Ensifer sp. AS08., Methods: We screened four amino acid residues of sNPEO-DH that are adjacent to the isoalloxazine ring of the coenzyme flavin adenine dinucleotide (FAD) by using multiple sequence alignment and homology modeling. Mutations were introduced by site-directed mutagenesis. The recombinant proteins were expressed, purified and assayed., Results: The relative activities of mutants N90A and N509A against the hydrophilic substrate PEG1000 decreased to 51% and 89%, respectively, and against the hydrophobic substrate NPEO(av10) decreased to 26% and 40%, respectively; indicating that N90 and N509 might be related to substrate binding. The relative activity of mutant H465A and N507A lost 90% and 100%, respectively; "stop-flow" experiments revealed that the processes of proton transfer from substrate to FAD and from FAD to enzyme were blocked in mutant N507A and H465A, respectively., Conclusion: Amino acid residues N507 and H465 located at the activity center of sNPEO-DH and play roles as catalytic sites for the oxidative dehydrogenation of the substrates and FADH2, respectively.