These cheat codes only work in the platform levels, i.e. they won't have any effect in the "Space Harrier" like shooter levels.
The cheat codes can only be entered when the game has been paused with the "F1" key, if sound effects/music are not disabled, a sample will be played if a correct cheat code has been entered.
ELIZIUM: refresh ammunition
IMPURITY: refresh energy
BOSSANOVA: kill enemy
RITUAL DE LO HABITUAL: add 10.000 to the score
[Source: StingRay, via message posted on EAB]