## 3 Results and Discussion
### Toxicity of Degradation Products
Figure 5: Effect of AFB1 and degradation products on cell viability of Hep G2 cells: (**A**) relative cell viability of AFB1 working solution in MTT assay (ns for not significant, * \(p\) \(<\) 0.05; **\(p\) \(<\) 0.01); (**B**) relative cell viability of AFB1 degradation products in MTT assay (* \(p\) \(<\) 0.05; **\(p\) \(<\) 0.01); (**C**) inverted microscope observation of Hep G2 cells in different treatments (scale bars: 100 \(\upmu\)m). Moreover, this study further evaluated the in vitro toxicity of AFB\({}_{1}\) degradation products by observing the effects of AFB\({}_{1}\) and its degradation products on the morphology of Hep G2 human hepatoma cells. Figure 5C shows the HepG2 human hepatoma cells observed in an inverted microscope after being cultured with different concentrations of AFB\({}_{1}\) working solution (0 \(\upmu\)g/mL, 2 \(\upmu\)g/mL, 20 \(\upmu\)g/mL, 100 \(\upmu\)g/mL, 200 \(\upmu\)g/mL, and 400 \(\upmu\)g/mL) and samples before and after degradation of AFB\({}_{1}\) by _Kocuria rosea_. In Figure 5C, Hep G2 cells treated with 0 \(\upmu\)g/mL AFB\({}_{1}\) working solution had extremely tight adhesion, high cell density, cells with smooth edges and clear outlines, and good cell adhesion. With the increase in AFB\({}_{1}\) working solution concentration, the cells gradually dispersed, the cell density gradually decreased, the cell folds increased, and the floating cells increased until the cells treated with 400 \(\upmu\)g/mL AFB\({}_{1}\) working solution were loose, the cell volume shrank, and the refractive transmittance became worse. In addition, there was a significant difference in the state of Hep G2 cells treated with AFB\({}_{1}\) cultured with _Kocuria rosea_ for 4 days and 0 days. The results showed that the toxicity of AFB\({}_{1}\) degradation products produced by _Kocuria rosea_ was significantly less than that of AFB\({}_{1}\). To observe the dead and living cells, this study further intuitively confirmed the extent of cell death by using different dyes to stain the dead and living cells combined with the effect of fluorescence microscopy on Hep G2 cells before and after AFB\({}_{1}\) degradation. PI enters dead cells through damaged cell membranes and binds to nucleic acids to produce red fluorescence. Therefore, red fluorescence can present dead cells. The living cells were stained green by Calcein-AM. As shown in Figure 6, both groups were significantly different from the control group before and after AFB\({}_{1}\) treatment with _Kocuria rosea_ (4 days and 0 days). The control group had many living cells, a high cell density, and tight adhesion, with only a few dead cells. Significant differences existed in the state and number of living cells between the 0-days group (AFB\({}_{1}\)) and the 4-days group (after AFB\({}_{1}\) degradation). In the 4-days group, the number of live cells significantly increased compared to the 0-days group; the cells were more tightly packed and aggregated, and there were fewer dead cells, which once again demonstrated that the toxicity of the degradation products of AFB\({}_{1}\) was lower than that of AFB\({}_{1}\).