Effect of Microwave Radiation on Growth, Enzyme Activity (Amylase and Pectinase), and/or Exopolysaccharide Production in Bacillus subtilis, Streptococcus mutans, Xanthomonas campestris and Pectobacterium carotovora

Aim: To investigate effect of microwave (MW) radiation on bacterial growth, enzyme activity (amylase and pectinase), and exopolysaccharide production.
Study Design: The study was designed to investigate effect of MW radiation on bacterial growth, enzyme activity, and exopolysaccharide production. Particularly the non-thermal effects were focused. Thermal effects were avoided (minimized) by keeping the bacterial suspension in ice while exposing to MW radiation.
Place and Duration of Study: Institute of Science, Nirma University, Ahmedabad, India, between November 2012 and May 2013.
Methodology: The present study investigated the effect of MW (90 W) radiation on bacterial growth, enzyme activity (amylase and pectinase), and exopolysaccharide (EPS) production. Test parameters viz. growth, enzyme activity, and EPS production of populations originated from MW treated cells were compared to those originated from untreated control. Thermal effects of MW radiation were avoided (minimized) by placing inoculum vial(s) in a ice containing beaker during MW exposure.
Results: MW treatment was found to be capable of altering bacterial growth, enzyme activity, and EPS production significantly. Amylase activity in B. subtilis suffered a heavy loss of 67.43% (P<0.01) following 6 min MW exposure. Pectinase activity in MW treated (4 min duration) B. subtilis was 169.92 times higher (P<0.01) than that of control. MW treatment for 4 min and 6 min duration were able to induce EPS production in Xanthomonas campestris by 46.15% (P<0.01) and 53.84% (P<0.05) respectively.
Conclusion: MW treatment was found to alter growth, enzyme activity, and EPS production significantly in the test bacteria. This study positively suggests existence of non-thermal effects of MW radiation on biological entities. Further investigation on mode of action of these MW specific athermal effects, and on their genetic stability are warranted.