Biofilm formation on agricultural waste pretreated with cold low-pressure nitrogen plasma and corona plasma discharges

Agricultural waste (AW) was pretreated with cold low-pressure nitrogen plasma (LPD) and corona atmospheric plasma discharges (CAPD), in an attempt to increase the bacterial attachment and biofilm formation. Biofilm formation was examined in the presence of exogenously added P. putida and B. cereus as well as in a sterile medium where only the indigenous bacteria which grow naturally on the wood surface could form biofilm. The exposure of AW to (LPD) led to a 3.5-fold increase in biofilm formation of the exogenously add P. putida F1 in MMT (minimal medium supplied with toluene) and a 1.6-fold increase in MMG (minimal medium supplied with glucose) compared to the untreated AW. The increase in biofilm formation was also observed with the exogenously added B. cereus or with indigenous bacteria that grow naturally on the AW. The effect of the CAPD on biofilm formation was weak. SEM analysis of the LPD-treated AW showed an increase in surface roughness, which we assume is one of the reasons for the enhancement of the biofilm formation. The apparent contact angle of a sessile drop on the surface of LPD-treated AW as well as on the bacterial layer showed their hydrophilic nature. In conclusion, the increase in biofilm formation of the exogenously added P. putida or B. cereus was due to the LPD treatment. Importance To the best of our knowledge, this is the first study to describe the effect of wood plasma treatment on biofilm formation. This technology can be further implemented for bioremediation of contaminated soils.