Hot Deformation Constitutive Analysis and Processing Maps of Ultrasonic Melt Treated A5052 Alloy.

Hot deformation constitutive analysis and processing maps of ultrasonic melt treated (UST) A5052 alloy were carried out based on a hot torsion test in this study. The addition of the Al-Ti master alloy as a grain refiner with no UST produced a finer grain size than the UST and pure Ti sonotrode. The Al3Ti phase particles in the case of the Al-10Ti master alloy acted as a nucleus for grain refinement, while the Ti atoms dissolved in the melt from the sonotrode were considered to have less of a grain refinement effect, even under UST conditions, than the Al3Ti phase particles in the Al-Ti master alloy. The constitutive equations for each experimental condition by torsion test were derived. In the processing maps examined in this study, the flow instability region was not present under UST in the as-cast condition, but it existed under the no UST condition. The effects of UST examined in this study are considered as (i) the uniform distribution of Ti solutes from the sonotrode and (ii) the reduction of pores by the degassing effect. After the homogenization heat treatment, most instability regions disappeared because the microstructures became uniform following the decomposition of intermetallic compounds and distribution of solute elements.

Animal-free production of hen egg ovalbumin in engineered Saccharomyces cerevisiae via precision fermentation.

To enable the sustainable production of ovalbumin (OVA) without relying on animal sources, the generally recognized as safe (GRAS) host Saccharomyces cerevisiae was used for the precision fermentation-based production of recombinant OVA. For this purpose, a signal peptide derived from EPX1, the most abundant extracellular protein produced by Pichia pastoris, was identified as a novel signal peptide for the efficient secretion of OVA in S. cerevisiae. To improve OVA secretion and cell growth, three helper proteins (PDI1, KAR2, and HAC1) present in the endoplasmic reticulum were expressed individually or in combination. Notably, the +P1/K2 strain coexpressing PDI1 and KAR2 with OVA produced 2 mg/L of OVA in the medium fraction; this value was 2.6-fold higher than the corresponding value for the control strain without helper proteins. Finally, a glucose-limited fed-batch fermentation process using the +P1/K2 strain yielded 132 mg/L of total OVA with 8 mg/L of extracellular OVA.

Metabolic engineering of Caldicellulosiruptor bescii for hydrogen production.

Hydrogen is an alternative fuel for transportation vehicles because it is clean, sustainable, and highly flammable. However, the production of hydrogen from lignocellulosic biomass by microorganisms presents challenges. This microbial process involves multiple complex steps, including thermal, chemical, and mechanical treatment of biomass to remove hemicellulose and lignin, as well as enzymatic hydrolysis to solubilize the plant cell walls. These steps not only incur costs but also result in the production of toxic hydrolysates, which inhibit microbial growth. A hyper-thermophilic bacterium of Caldicellulosiruptor bescii can produce hydrogen by decomposing and fermenting plant biomass without the need for conventional pretreatment. It is considered as a consolidated bioprocessing (CBP) microorganism. This review summarizes the basic scientific knowledge and hydrogen-producing capacity of C. bescii. Its genetic system and metabolic engineering strategies to improve hydrogen production are also discussed. KEY POINTS: • Hydrogen is an alternative and eco-friendly fuel. • Caldicellulosiruptor bescii produces hydrogen with a high yield in nature. • Metabolic engineering can make C. bescii to improve hydrogen production.