The metabolic engineering of Escherichia coli for the high-yield production of hypoxanthine.

Background: Hypoxanthine, prevalent in animals and plants, is used in the production of food additives, nucleoside antiviral drugs, and disease diagnosis. Current biological fermentation methods synthesize quantities insufficient to meet industrial demands. Therefore, this study aimed to develop a strain capable of industrial-scale production of hypoxanthine.

Productivity enhancement in L-lysine fermentation using oxygen-enhanced bioreactor and oxygen vector.

L-lysine is a bulk product. In industrial production using high-biomass fermentation, the high density of bacteria and the intensity of production require sufficient cellular respiratory metabolism for support. Conventional bioreactors often have difficulty meeting the oxygen supply conditions for this fermentation process, which is not conducive to improving the sugar-amino acid conversion rate.

Metabolic engineering of Escherichia coli for efficient production of L-5-hydroxytryptophan from glucose.

Background: 5-hydroxytryptophan (5-HTP), the direct biosynthetic precursor of the neurotransmitter 5-hydroxytryptamine, has been shown to have unique efficacy in the treatment of a variety of disorders, including depression, insomnia, and chronic headaches, and is one of the most commercially valuable amino acid derivatives. However, microbial fermentation for 5-HTP production continues to face many challenges, including low titer/yield and the presence of the intermediate L-tryptophan (L-Trp), owing to the complexity and low activity of heterologous expression in prokaryotes. Therefore, there is a need to construct an efficient microbial cell factory for 5-HTP production.

Process study of ceramic membrane-coupled mixed-cell fermentation for the production of adenine.

In order to solve the problems of high complexity, many by-products, high pollution and difficult extraction of the existing adenine production process, in this study, ceramic membrane-coupled mixed cell fermentation was used to produce adenine while reducing the synthesis of by-products and simplifying the production process of adenine. Nucleoside hydrolase (encoded by the gene) was used to produce adenine by coordinated fermentation with the adenosine-producing bacterium XGL. The adenosine hydrolase (AdHy)-expressing strain BL21-AdHy was successfully employed and the highest activity of the crude enzyme solution was found by orthogonal experiments at 170 W power, 42% duty cycle, and 8 min of sonication.

Effect of low-level ultrasound treatment on the production of L-leucine by in fed-batch culture.

Various process intensification methods were proposed to improve the yield, quality, and safety of fermented products. Here, we report the enhancement of L-leucine production by CP using ultrasound-assisted fed-batch fermentation. Response surface methodology was employed to optimize the sonication conditions.

Focus properties of cosh-Gaussian beams with the power-exponent-phase vortex.

Vector diffraction theory is used to investigate the focusing properties of cosh-Gaussian beams with the power-exponent-phase vortex. The effects of the decentered parameter, the power order, and the topological charge on the normalized intensity distribution are examined. Results show that intensity distribution in the focal region can be altered significantly by the topological charge, the power order, and the decentered parameter.

Effective tensor approach for simulating the propagation of partially coherent Hermite-sinh-Gaussian beams through an ABCD optical system in turbulent atmosphere.

An efficient tensor approach is used to simulate the propagation of partially coherent Hermite-sinh-Gaussian (H-ShG) beams through an ABCD optical system in a turbulent atmosphere. Analytical expressions for the average intensity are derived. The properties of the average intensity of the beam are studied numerically.

A patient-specific haptic drilling simulator based on virtual reality for dental implant surgery.

Purpose: In the dental implant surgery, there are inevitable risks due to the anatomically complex operation in the cranio-maxillofacial region. Therefore, there is a trend to use computer-aided technology to simulate the process of the implant surgery. In this study, we present a haptic simulator for trainees to study and rehearse the drilling performance of dental implant surgery.

Mechanism study on stability enhancement of adefovir dipivoxil by cocrystallization: Degradation kinetics and structure-stability correlation.

The purpose of this study is to determine the mechanism by which cocrystallization can enhance the stability of adefovir dipivoxil (AD), a diester prodrug of adefovir with known chemical stability problem. Three multi-component crystals of AD with biologically safe coformers, including gallic acid cocrystal hydrate (1:1:1), salicylate salt (1:1), and maleate salt (1:1) were prepared and characterized by thermal analysis, infrared spectroscopy, powder and single crystal X-ray diffraction. DVS measurements and stability tests were applied to evaluate the stability.