Characteristics of a Rollable Dielectric Barrier Discharge Plasma and Its Effects on Spinach-Seed Germination.

We investigated the characteristics of a rollable dielectric barrier discharge (RDBD) and evaluate its effects on seed germination rate and water uptake. The RDBD source was composed of a polyimide substrate and copper electrode, and it was mounted in a rolled-up structure for omnidirectional and uniform treatment of seeds with flowing synthetic air gas. The rotational and vibrational temperatures were measured to be 342 K and 2860 K, respectively, using optical emission spectroscopy. The chemical species analysis via Fourier-transform infrared spectroscopy and 0D chemical simulation showed that O3 production was dominant and NOx production was restrained at the given temperatures. The water uptake and germination rate of spinach seeds by 5 min treatment of RDBD was increased by 10% and 15%, respectively, and the standard error of germination was reduced by 4% in comparison with the controls. RDBD enables an important step forward in non-thermal atmospheric-pressure plasma agriculture for omnidirectional seed treatment.

Plasma-mediated enhancement of enzyme secretion in Aspergillus oryzae.

Technical bottlenecks in protein production and secretion often limit the efficient and robust industrial use of microbial enzymes. The potential of non-thermal atmospheric pressure plasma to overcome these technical barriers was examined. Spores of the fermenting fungus Aspergillus oryzae (A. oryzae) were submerged in potato dextrose broth (PDB) (5 × 106 per ml) and treated with micro dielectric barrier discharge plasma at an input voltage of 1.2 kV and current of 50 to 63 mA using nitrogen as the feed gas. The specific activity of α-amylase in the broth was increased by 7.4 to 9.3% after 24 and 48 h of plasma treatment. Long-lived species, such as NO2 - and NO3 - , generated in PDB after plasma treatment may have contributed to the elevated secretion of α-amylase. Observations after 24 h of plasma treatment also included increased accumulation of vesicles at the hyphal tip, hyphal membrane depolarization and higher intracellular Ca2+ levels. These results suggest that long-lived nitrogen species generated in PDB after plasma treatment can enhance the secretion of α-amylase from fungal hyphae by depolarizing the cell membrane and activating Ca2+ influx into hyphal cells, eventually leading to the accumulation of secretory vesicles near the hyphal tips.