Photodegradation of organic waste coupling hydrogenase and titanium dioxide

In this work the results of the study on the degradation of dairy waste and lactose with use of titanium dioxide (TiO2), as photocatalyst, are presented. The ability of TiO2 to degrade dairy waste is compared either in the presence of molecular oxygen or of a bacterial hydrogenase as electron acceptor. The enzyme-mediated H2 production rates or the O2 consumption rates are used to measure electron donor degradation. The results obtained clearly indicate that dairy waste can be degraded by the TiO2 photocatalyst. Proteins present in the dairy waste have a strong inhibitory effect on the degradation process. Indeed lactose alone can easily be degraded. When the protein extract obtained from the dairy waste was added to the lactose solution, the reaction for both electron acceptors, hydrogenase and oxygen, was inhibited. When the dairy waste solutions were diluted, there was a positive effect on the reaction rate. This was particularly true in the case of hydrogenase, and to a lesser extent in the case of oxygen acceptor. The reduction of the pH from 8 to 6 also increased H2 production when the enzyme was used.