Development of simultaneous substrate mixer and cold atmospheric plasma treatment for mushroom cultivation

Abstract

The purpose of this study is to design and develop a substrate mixer for mushroom cultivation and also to investigate the effect of Cold Atmospheric Plasma (CAP) treatment on the substrate. Three design concepts were developed to enable evaluation on function of the substrate mixer. System design procedure such as using morphology chart and Pugh's method was adopted to carry out the analysis on function and performance. This analysis was conducted in order to get the most suitable functional and performance design criteria selection for the mixer mechanism. The ability of mixer mechanism includes the function of mixing and transporting process was selected. The prototype with spiral stirrer was fabricated by using 3D printing machine of FDM technology. An atmospheric pressure plasma jet (APPJ) system was used for the plasma generation method. In order to undergo the decontamination treatment, APPJ system was assembled to the substrate mixer. The substrates were placed directly under the plasma tube within gap of 10mm with selected treatment time. Samples were treated at 5 kV supplied voltage for treatment time of 5min, 10min and 15min and an untreated sample as control. Analysis had been conducted by using Colony Forming Unit (CFU) testing to know the amount of growth bacteria for the non-treated and treated of mushroom substrate. Results show that all CAP treated substrate had significant reduction in bacteria growth. It is found that 15min treatment indicates the lowest bacteria growth in CFU unit.