*2.5. Determination of Lipid Peroxidation*

Malondialdehyde (MDA) is an end product of lipid peroxidation. Therefore estimation of MDA through its reaction with thiobarbituric acid (TBA), forming a pink colored MDA-TBA complex, predicts the disintegration or, rather the damage of microbial cell membrane leading to death [16–18]. To establish this, analysis was performed by obtaining 1 mL samples from the reactor contents at regular time intervals (5 min) and the samples were mixed with 2 mL of 10% (wt./vol.) trichloroacetic acid. The mixture was subjected to centrifugation at 11,000 *g* for initial 35 min and then again for an additional 20 min to ensure the removal of precipitated proteins, catalyst, cells and other possible solid components from the system [16]. 3 mL of freshly prepared 0.67% (wt./vol.) TBA (Sigma Aldrich) was added to the supernatant. The samples were boiled in a water bath for 10 min and then the absorbance was measured at 532 nm using UV-visible spectrophotometer. The concentration of MDA in the system was calculated in nanomoles of MDA released per mg dry weight of bacteria [18].
