Engineering an aldehyde dehydrogenase toward its substrates, 3-hydroxypropanal and NAD(+), for enhancing the production of 3-hydroxypropionic acid

3-Hydroxypropionic acid (3-HP) can be produced via the biological route involving two enzymatic reactions: dehydration of glycerol to 3-hydroxypropanal (3-HPA) and then oxidation to 3-HP. However, commercial production of 3-HP using recombinant microorganisms has been hampered with several problems, some of which are associated with the toxicity of 3-HPA and the efficiency of NAD(+) regeneration. We engineered a-ketoglutaric semialdehyde dehydrogenase (KGSADH) from Azospirillum brasilense for the second reaction to address these issues. The residues in the binding sites for the substrates, 3-HPA and NAD(+), were randomized, and the resulting libraries were screened for higher activity. Isolated KGSADH variants had significantly lower Km values for both the substrates. The enzymes also showed higher substrate specificities for aldehyde and NAD(+), less inhibition by NADH, and greater resistance to inactivation by 3-HPA than the wild-type enzyme. A recombinant Pseudomonas denitrificans strain with one of the engineered KGSADH variants exhibited less accumulation of 3-HPA, decreased levels of inactivation of the enzymes, and higher cell growth than that with the wild-type KGSADH. The flask culture of the P. denitrificans strain with the mutant KGSADH resulted in about 40% increase of 3-HP titer (53 mM) compared with that using the wild-type enzyme (37 mM)

Measurement of Hand-Arm Vibration Syndrome of an Agricultural Tractor Steering Wheel using Machine Vision System

The structure of an agricultural tractor is a structure without a suspension system to limit the vibrations generated by its engine. It exposed the entire body of an agricultural tractor operator to vibration. Thus, the body of the driver, constantly exposed to the vibration, becomes fatigued. This fatigue becomes a factor in the driver's inattention. The driver’s body has transmitted to vibration through the tractor's seat, accelerator pedal, brake pedal, and steering wheel. Quantifying seat, accelerator pedal, brake pedal, and steering wheel vibrations is one of the most important factors in determining the cause of vibration and correcting it. The ISO 5349 standard lays down a guideline for the measurement and assessment of vibrations transmitted by the human hand. To meet the ISO 5349 standard, assess human exposure to hand-transmitted vibration and meet the human subjective comfort level. It must keep the vibration within a specified range. This study attempts to measure steering wheel vibrations through a new machine vision system using up-sampled cross correlation and a Discrete Finite Transform algorithm. In this study, it was impossible to calculate vibration in three axes from the video images recorded by the camera. According to ISO 5349-2, the vibration obtained on two axes multiplied by 1 to 1.7 to calculate the equivalent measurement for the vibration on the third axis. The results show that when the vibration is high; the errors are less and when the vibration is low, near zero, the errors range from 30 % to 50 %. But this study suggests that very low-level vibrations are unnecessary for vibration analysis. This study is not suitable for Nano-vibration measurement methods that measure fine vibrations

Microwave sintering of nickel ferrite nanoparticles processed via sol-gel method

Magnetic nickel ferrite (NiFe2O4) was prepared by sol-gel process and calcined in the 2.45 GHz singlemode microwave furnace to synthesize nickel nanopowder. The sol-gel method was used for the processing of the NiFe2O4 powder because of its potential for making fine, pure and homogeneous powders. Sol-gel is a chemical method that has the possibility of synthesizing a reproducible material. Microwave energy is used for the calcining of this powder and the sintering of the NiFe2O 4 samples. Its use for calcination has the advantage of reducing the total processing time and the soak temperature. In addition to the above combination of sol-gel and microwave processing yields to nanoscale particles and a more uniform distribution of their sizes. X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy and vibrating sample magnetometer were carried out to investigate structural, elemental, morphological and magnetic aspects of NiFe2O4. The results showed that the mean size and the saturation magnetization of the NiFe 2O4 nanoparticles are about 30 nm and 55.27 emu/g, respectively. This method could be used as an alternative to other chemical methods in order to obtain NiFe2O4 nanoparticles