Oxidative stress induced by plasma-activated water stimulates astaxanthin production in Phaffia rhodozyma

Astaxanthin is used extensively in the nutraceutical, aquaculture, and cosmetic industries. The current market necessitates higher astaxanthin production from Phaffia rhodozyma (P. rhodozyma) due to its higher cost compared to chemical synthesis. In this study, a bubble discharge reactor was developed to generate plasma-activated water (PAW) to produce PAW-made yeast malt (YM) medium. Due to oxidative stress induced by PAW, strains cultured in 15 and 30 min-treated PAW-made medium produced 7.9 ± 1.2 % and 12.6 ± 1.4 % more carotenoids with 15.5 ± 3.3 % and 22.1 ± 1.3 % more astaxanthin, respectively. Reactive oxygen species (ROS) assay results showed that ROS generated by plasma-water interactions elevated intracellular ROS levels. Proteomic analysis revealed increased expression of proteins involved in the cellular response to oxidative stress as well as carotenoid biosynthesis, both of which contribute to higher yields of astaxanthin. Overall, this study supports the potential of PAW to increase astaxanthin yields for industrial-scale production.

Insights into amoxicillin degradation in water by non-thermal plasmas

Antibiotics have been extensively used as pharmaceuticals for diverse applications. However, their overuse and indiscriminate discharge to water systems have led to increased antibiotic levels in our aquatic environments, which poses risks to human and livestock health. Non-thermal plasma water. However, the issues of process scalability and the mechanisms towards understanding the plasma-induced degradation remain. This study addresses these issues by coupling a non-thermal plasma jet with a continuous flow reactor to reveal the effective mechanisms of amoxicillin degradation. Four industry-relevant feeding gases (nitrogen, air, argon, and oxygen), discharge voltages, and frequencies were assessed. Amoxicillin degradation efficiencies achieved using nitrogen and air were much higher compared to argon and oxygen and further improved by increasing the applied voltage and frequency. The efficiency of plasma-induced degradation depended on the interplay of hydrogen peroxide (H₂O₂) and nitrite (NO₂^-), validated by mimicked chemical solutions tests. Insights into prevailing degradation pathways were elucidated through the detection of intermediate products by advanced liquid chromatography-mass spectrometry.

Bactericidal Silver Nanoparticles by Atmospheric Pressure Solution Plasma Processing

Silver nanoparticles have applications in plasmonics, medicine, catalysis and electronics. We report a simple, cost-effective, facile and reproducible technique to synthesise silver nanoparticles via plasma-induced non-equilibrium liquid chemistry with the absence of a chemical reducing agent. Silver nanoparticles with tuneable sizes from 5.4 to 17.8 nm are synthesised and characterised using Transmission Electron Microscopy (TEM) and other analytic techniques. A mechanism for silver nanoparticle formation is also proposed. The antibacterial activity of the silver nanoparticles was investigated with gram-positive and gram-negative bacteria. The inhibition of both bacteria types was observed. This is a promising alternative method for the instant synthesis of silver nanoparticles, instead of the conventional chemical reduction route, for numerous applications.

Bioproducts From Euglena gracilis: Synthesis and Applications

In recent years, the versatile phototrophic protist Euglena gracilis has emerged as an interesting candidate for application-driven research and commercialisation, as it is an excellent source of dietary protein, pro(vitamins), lipids, and the β-1,3-glucan paramylon only found in euglenoids. From these, paramylon is already marketed as an immunostimulatory agent in nutraceuticals. Bioproducts from E. gracilis can be produced under various cultivation conditions discussed in this review, and their yields are relatively high when compared with those achieved in microalgal systems. Future challenges include achieving the economy of large-scale cultivation. Recent insights into the complex metabolism of E. gracilis have highlighted unique metabolic pathways, which could provide new leads for product enhancement by genetic modification of the organism. Also, development of molecular tools for strain improvement are emerging rapidly, making E. gracilis a noteworthy challenger for microalgae such as Chlorella spp. and their products currently on the market.

Development of screening strategies for the identification of paramylon-degrading enzymes

Enzymatic degradation of the β-1,3-glucan paramylon could enable the production of bioactive compounds for healthcare and renewable substrates for biofuels. However, few enzymes have been found to degrade paramylon efficiently and their enzymatic mechanisms remain poorly understood. Thus, the aim of this work was to find paramylon-degrading enzymes and ways to facilitate their identification. Towards this end, a Euglena gracilis-derived cDNA expression library was generated and introduced into Escherichia coli. A flow cytometry-based screening assay was developed to identify E. gracilis enzymes that could hydrolyse the fluorogenic substrate fluorescein di-β-D-glucopyranoside in combination with time-saving auto-induction medium. In parallel, four amino acid sequences of potential E. gracilis β-1,3-glucanases were identified from proteomic data. The open reading frame encoding one of these candidate sequences (light_m.20624) was heterologously expressed in E. coli. Finally, a Congo Red dye plate assay was developed for the screening of enzyme preparations potentially able to degrade paramylon. This assay was validated with enzymes assumed to have paramylon-degrading activity and then used to identify four commercial preparations with previously unknown paramylon degradation ability.