Roles of oxides of nitrogen on quality enhancement of soybean sprout during hydroponic production using plasma discharged water recycling technology

This study was performed to assess the effect of plasma-discharged water recycling technology as irrigation water on soybean sprout production. Two different types of irrigation water were used individually for cultivation, including plasma discharged water as a source of oxides of nitrogen and tap water, irrigation water was recycled for every 30 minutes. Plasma discharged irrigation water reduced overall 4.3 log CFU/ml aerobic microbe and 7.0 log CFU/ml of artificially inoculated S. Typhimurium within 5 minutes and 2 minutes, respectively, therefore sprout production occurs in a hygienic environment. Using of plasma-discharged water for cultivation, increases the amount of ascorbate, asparagine, and γ-aminobutyric acid (GABA) significantly (p < 0.05), in the part of cotyledon and hypocotyl of soybean sprout during 1 to 4 days of farming. A NO scavenger, 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (cPTIO), was added in irrigation water to elucidate the roles of the oxides of nitrogen such as NO(3)(−), NO(2)(−) generated in plasma discharged water. It was observed that all three nutrients decreased in the cotyledon part, whereas ascorbate and GABA contents increased in the hypocotyl and radicle part of bean sprout for the same duration of farming. The addition of NO scavenger in the irrigation water also reduced growth and overall yield of the soybean sprouts. A recycling water system with plasma-discharged water helped to reduce the amount of water consumption and allowed soybean sprouts growth in a hygienic environment during the hydroponic production.