Life is like a rocket
It needs a reducing agent and an oxidising agent. Just about any chemical imbalance will do. Some bugs live off Sulphur/Sulphate redox gradients. Others on O2/CO/CO2, some on CH4-O2, etc...
On Titan you would need an oxidant to combine with the prevalant reducing atmosphere. On Earth we burn reducing agents in the prevalent oxidising atmosphere. (And on Earth the oxygen is the outcome of billions of years of life and the burial of reduced organic material from the original broadly neutral/mildly reducing atmosphere and hydrosphere)