Abstract
In a previous study, we found that plasma can enhance spore germination and α-amylase secretion in A. oryzae, a beneficial fungus used in fermentation. To confirm this, in the current study, we investigated the effects of plasma on development and α-amylase secretion using an enlarged sample size and a different plasma source: a plasma jet. There was a ~10% (p < 0.01) increase in spore germination upon non-thermal atmospheric pressure plasma jet (NTAPPJ) treatment for 5 min and 10 min, as compared with the control (no plasma treatment). The activity of α-amylase detected in potato dextrose broth (PDB) media during incubation was significantly elevated in plasma-treated samples, with a more obvious increase upon 10 min and 15 min treatments and 24–96 h incubation periods. The levels of the oxidation reduction potential (ORP) and NOX (nitrogen oxide species) were higher in the plasma-treated samples than in the control samples, suggesting that these two variables could serve as standard indicators for enhancing α-amylase activity after plasma treatment. Genome sequencing analysis showed approximately 0.0016–0.0017% variations (changes in 596–655 base pairs out of a total of 37,912,014 base pairs) in the genomic DNA sequence of A. oryzae after plasma treatment. Our results suggest that NATPPJ can enhance the spore germination and extracellular activity of α-amylase, probably by increasing the levels of ORP and NOX to an optimum level.
Highlights
At present, the demand for enzymes is increasing in different industrial activities, such as chemistry, food, textiles, and pharmaceuticals
Our results demonstrated that the plasma jet, like the micro-DBD plant-type plasma used in our previous study, can promote the germination of fungal spores and α-amylase activity in media
We demonstrated that the scaled-up treatment of A. oryzae spores with an Non-thermal atmospheric pressure plasma (NTAPP) jet could enhance the spore germination and activity of α-amylase in the potato dextrose broth (PDB) media at the hyphal stage
Summary
The demand for enzymes is increasing in different industrial activities, such as chemistry, food, textiles, and pharmaceuticals. The food industry is continuously demanding enzymes for use in fermentation and other processes. Α-amylase is one such enzyme with high demand in starch-processing industries, such as those involved in the production of glucose syrups, bread, and alcoholic beverages, because it is used for the hydrolysis of starch into simple sugar components. Wild-type and genetically modified microorganisms have been considered good producers of food enzymes because those are more stable and steadily active, compared with plant and animal enzymes [2,3,4]. Technology development is necessary to improve the efficiency of enzyme production and to ensure that the process is simple, fast, safe, and involves a low cost
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