To decompose and decolor melanoidine or melanoidine-like material growing an useful filiform bacteria by a method wherein operation is carried out by using cellulose as a mutrition source of a cellulose utilization filiform bacteria.

As a nutrition source of cellulose utilization filform bacteria in a method wherein melanoidine or melanoidine-like material is decolored and decomposed by using a filiform bacteria. As the filiform bacteria to be used, a bacteria producing manganese peroxidase and lignin peroxidase relating to decomposition and decoloration of the melanoidine and a bacteria having a lignin decomposing function are preferable. Though cellulose is used as the nutrition source of the filiform bacteria, an addition form of the filiform bacteria is not especially limited, it may be added in any form of a powder state, a pellet state, or a pulp state, a carrier fixing a useful filiform bacteria is a cellulose made carrier, and this carrier may be incorporated into an apparatus from the begining.