## 4 Discussion
Further studies are needed to assess the pressure and temperature variations inside the microwave system, including the culture medium, similar to the existing measurements of these parameters in autoclaves [29; 30; 31]. A comparison of media productivity using both systems was performed with culture media (solids and liquids) widely used in laboratories for the microbiological quality analysis of food, cosmetics, and pharmaceutical products. In addition, the media exposed for the different exposure times in the microwave were assessed, with an overall view of how the sterilization method and sterilization times affected the microbiological properties of the culture media. The tendency of yeasts in an SDA medium to grow better in a microwave-sterilized medium than in an autoclaved medium could be attributed to the generation of toxic compounds; for example, due to Maillard reactions, the culture media darkens, being produced after the long exposure of the medium to high temperatures [4; 5; 12], which can inhibit the growth of certain micro-organisms [7; 32; 33]. Culture media containing simple sugars, such as SDA, are more likely to generate these Maillard reaction compounds than other culture media, and this process could be more pronounced in the autoclave than in the microwave system [7]. For SDA, a correlation of medium browning with the exposure time in the microwave was observed. Exposures of 7-10 min rendered a clearer medium than the rest of the exposure times and the autoclave method. This could explain the increased growth, in certain cases, in media exposed to the microwave versus the autoclave. For both yeasts (i.e., _C. albicans_ and _S. cerevisiae_), increased growth was observed with longer exposure times in the microwave oven, possibly due to their tolerance to pH variations [34]. On the other hand, the growth of _A. brasiliensis_ in SDA was very similar in all conditions assayed. Growth in regard to SDA sterilized with this system deserves further research, as increased productivity could speed up detection in microbiological controls, food, and medicinal products that are characterized as requiring prolonged periods of incubation. Improvements in the growth of some micro-organisms were also observed in the TSA sterilized in the microwave, particularly _S. aureus_, _B. subtilis_, and _L. monocytogenes_, probably due to the lower generation of toxic compounds, such as ROS, the oxidation of certain compounds produced to a greater extent at higher temperatures, and the Maillard reaction between the agar and peptones [6]. The increased growth of _S. aureus_ and _L. monocytogenes_ could be particularly relevant for detection in food and clinical samples, where the usefulness of the microwave system should be tested with respect to the corresponding selective media. In the cases of _P. aeruginosa_, _C. perfringens_, and _A. brasiliensis_, lower growth was observed in the TSA sterilized in the microwave compared to the autoclaved media. TSA is not the optimum medium for the growth of _A. brasiliensis_ and, as reported above, growth in regard to SDA prepared with the new system yielded similar growth to the autoclaved SDA. In the case of _C. perfringens_, in routine practice, selective culture media are used, such as SPS or tryptpose sulfite cycloserine (TSC), which could also be assessed using this system. In the case of _P. aeruginosa_, the lower growth detected in the microwave media could also be an advantage for the manufacturing of certain selective media, in which the inhibition of _Pseudomonas_ often constitutes a challenge, as it concerns samples used for the analysis of water samples, where _Pseudomonas_ is often the main interfering micro-organism [8]. Finally, for the selective media VRBG, which is commonly prepared by boiling, relevant growth increases were observed, particularly for _E. coli_ ATCC 25922, _S._ ser. Typhimurium, and _P. aeruginosa_.