生物 せいぶつ分解 ぶんかいじゃありませんでした
biseibutsubunkaijārimasendeshita

Noun
Desu Copula

The polite, past negative form of 微生物分解

1. It was not microbial decomposition.; It wasn't biodegraded by microbes.

Past/Perfective
Negative
Polite
Terminal Form