The microbes used for environmental purposes, e.g. treat wastewater and transform waste, are not yet well understood. However, the technical progress made in microbial analysis over the past few years has provided the means to pursue the study of their complexity. The Cemagref teams and their partners in the ANR ECCO project¹ are among the leading researchers in France in this field. Since 2003, they have studied the functions carried out by the micro-organisms involved in the degradation of waste in the absence of oxygen, by combining isotopic marking techniques and molecular microbiology. The researchers identified the various bacteria involved in the degradation of cellulose, selected for its representative value, in facilities designed to store household waste and produce methane as a biogas with potential for recovery and use.

Two techniques and a giant step in understanding microbial functions

The cellulose, marked with the stable carbon 13 (13C) isotope, is ingested by the degrading microbes and the 13C thus becomes part of their DNA. Once isolated, the DNA is used to identify the micro-organisms involved in the degradation process. The Cemagref teams then determine their function more precisely by measuring the amount of 13C absorbed by each cell. In conjunction with mathematical models, this measurement reveals the role played by each group of micro-organisms in the process of cellulose degradation. The hydrolysis step, in particular, is carried out by the Acetivibrio² group. The successful combination of isotopic and molecular techniques will make it possible to control the bacterial functions within systems.

Mimicking life?

These techniques can also be applied to other fields, such as water treatment, soil biodegradation, etc., or be used to better understand and copy life itself. Natural selection taking place over thousands of years enabled ruminants and termites to develop an intestinal flora capable of degrading cellulose ten times more efficiently than an industrial digester. Another part of the project consists of comparing these different systems and identifying the differentiating factors. This work to improve the efficiency of waste degradation is already being carried out in collaboration with industrial companies in the sector.