Nuclear fusion in DT, 6LiD, 7LiD, p11B, 10BD, 3HeD and other mixtures is considered using a time dependent model based on 44 nuclear reactions, including ion-electron collisions, bremsstrahlung losses and mechanical expansion. The effect of the initial tritium concentration on ignition temperature, neutron production and energy gain is analysed. It is found that tritium seeding can help ignite DD, 3HeD and 7LiD reactions. However, the effect is not so important in aneutronic fuels, such as 11BH. In all cases, all possible fusion reactions must be taken into account to optimize the plasma performance, for instance, to minimize the ignition temperature. Another important finding is the possibility of a catalytic regime for tritium in several fuels, without needing external tritium breeding and reducing the tritium inventory