Molecular Mechanisms for Anti-aging of Low-Vacuum Cold Plasma Pretreatment in Caenorhabditis elegans

Cold Plasma Treatment Facilitated the Conversion of Lignin-Derived Aldehyde for Pseudomonas putida

Syringaldehyde derived from lignin is one of the essential intermediates for the production of basic chemicals. However, it was poorly understood for the direct microbial conversion of syringaldehyde. Here, this study tried to use cold plasma technique to enhance syringaldehyde conversion for the bacterium Pseudomonas putida. It illustrated that cell growth and syringaldehyde conversion were separately increased by 1.49 times at 3 h and 1.60 times at 6 h for 35 s, 1.16 and 3.44 times for 140 W, and 1.63 and 4.02 times for 105 Pa for P. putida through single factor assays of cold plasma treatment. To be sure, cell growth and syringaldehyde conversion were enhanced by 1.14 and 5.54 times at 3 h under the optimum parameters (35 s, 140 W, and 105 Pa) for P. putida. Furthermore, genome re-sequencing further discovered single-nucleotide polymorphisms of P. putida, such as PP_2589 (A428V), PP_5651 (V82F), and PP_0545 (W335R), and thus indicated that the potential genetic changes derived from cold plasma treatment would be responsible for the acceleration of syringaldehyde conversion. This work would provide a robust strain catalyst and the potential candidate mutation sites for genetic manipulation for microbial bioconversion of the value-added and lignin-based biochemicals.

Investigating the effect of plasma activated water on entomopathogenic nematodes under laboratory conditions

Entomopathogenic nematodes are currently being tested for their efficiency in controlling several insect pests. In recent years, non-thermal plasma has been investigated as a state-of-the-art technology for its disinfection/decontamination properties on the seed surface. In addition, it is also used to induce seed germination. In this investigation, the effect of plasma activated water (PAW) was tested on three EPN species, namely Steinernema feltiae Filipjev (1934), S. carpocapsae Weiser (1955), and Heterorhabditis bacteriophora Poinar (1976). Seven different PAW prepared at different treatment times, that is, (1s, 3s, 5s, 10s, 20s, 60s, 90s) were tested directly on the three selected nematode species. Distilled water was used as a control treatment (0s). In the case of H. bacteriophora, significantly higher mortality was observed in PAW preparation times of 5, 10, 20, 60 and 90s compared to the control. In the case of S. feltiae, significantly high mortality was observed for PAW preparation times of 10, 20, 60 and 90s. However, S. carpocapsae was found to have the least sensitivity against all PAW treatments, with a maximum mortality of 14 % (<20 %), indicating the potential synergy between PAW and EPNs. The possibility of combined treatments in the context of integrated pest management is presented and discussed.

Effects of Cold Plasma Pretreatment on the Synthesis of Polysaccharide from Pleurotus ostreatus

Fungal polysaccharides have attracted wide attention because of their medical pharmaceutical and health care value. So far, many efforts have been made in strain improvement to produce polysaccharides on a large scale at low cost. Here, a novel cold plasma-induced strain improvement technology was employed to pretreat Pleurotus ostreatus CGMCC 5.374 by radio-frequency (RF) low-vacuum cold plasma (LVCP) for the purpose of obtaining a high-yield polysaccharide strain. The optimum pretreatment conditions including discharge power, treatment time, and working pressure were determined by single factor and orthogonal experiment in succession. Furthermore, transcriptome analysis was conducted to study the effects of RF-LVCP on cell metabolism and proliferation. Results showed that under the optimal condition of discharge power of 130 W, treatment time of 25 s and working pressure of 140 Pa, polysaccharide content in mycelium was increased by 3.16% after 6 days in comparison to the original strain. Transcriptome analysis showed that RF-LVCP is helpful for specific gene transcription profiles, Gene Ontology (GO) and KEGG pathways, of which the differentially expressed genes (DEGs) were mainly involve with the up-regulation of polysaccharide transport, physiology, synthesis and metabolism, as well as the down-regulation of polysaccharide hydrolysis and macromolecular degradation.

Cold plasma pretreatment reinforces the lignocellulose-derived aldehyde inhibitors tolerance and bioethanol fermentability for Zymomonas mobilis

BACKGROUND

Lignocellulose-derived aldehyde inhibitors seriously blocked the biorefinery of biofuels and biochemicals. To date, the economic production of lignocellulose-based products heavily relied on high productivities of fermenting strains. However, it was expensive and time-consuming for the achievable rational modification to strengthen stress tolerance robustness of aldehyde inhibitors. Here, it aimed to improve aldehyde inhibitors tolerance and cellulosic bioethanol fermentability for the chassis Zymomonas mobilis ZM4 pretreated using energy-efficient and eco-friendly cold plasma.

RESULTS

It was found that bioethanol fermentability was weaker in CSH (corn stover hydrolysates) than that in synthetic medium for Z. mobilis, and thus was attributed to the inhibition of the lignocellulose-derived aldehyde inhibitors in CSH. Convincingly, it further confirmed that the mixed aldehydes severely decreased bioethanol accumulation through additional aldehydes supplementary assays in synthetic medium. After assayed under different processing time (10-30 s), discharge power (80-160 W), and working pressure (120-180 Pa) using cold atmosphere plasma (CAP), it achieved the increased bioethanol fermentability for Z. mobilis after pretreated at the optimized parameters (20 s, 140 W and 165 Pa). It showed that cold plasma brought about three mutation sites including ZMO0694 (E220V), ZMO0843 (L471L) and ZMO0843 (P505H) via Genome resequencing-based SNPs (single nucleotide polymorphisms). A serial of differentially expressed genes (DEGs) were further identified as the potential contributors for stress tolerance via RNA-Seq sequencing, including ZMO0253 and ZMO_RS09265 (type I secretion outer membrane protein), ZMO1941 (Type IV secretory pathway protease TraF-like protein), ZMOr003 and ZMOr006 (16S ribosomal RNA), ZMO0375 and ZMO0374 (levansucrase) and ZMO1705 (thioredoxins). It enriched cellular process, followed by metabolic process and single-organism process for biological process. For KEGG analysis, the mutant was also referred to starch and sucrose metabolism, galactose metabolism and two-component system. Finally, but interestingly, it simultaneously achieved the enhanced stress tolerance capacity of aldehyde inhibitors and bioethanol fermentability in CSH for the mutant Z. mobilis.

CONCLUSIONS

Of several candidate genetic changes, the mutant Z. mobilis treated with cold plasma was conferred upon the facilitated aldehyde inhibitors tolerance and bioethanol production. This work would provide a strain biocatalyst for the efficient production of lignocellulosic biofuels and biochemicals.