A method for processing plant matter, which involves applying a processing composition including at least one biological agent selected from: bacteria including a DNA sequence, referred to as 16S rDNA, coding for the 16S ribosomal RNA of the bacterium, which is 100% homologous with SEQ ID NO. 1, culture media in which bacteria have grown which include the 16S rDNA sequence that is 100% homologous with SEQ ID NO. 1 and which are substantially free of the bacteria, the culture media including polynucleotides having a DNA sequence which is 100% homologous with SEQ ID NO. 1, and in which the bacteria are selected from bacteria that are consistent with the strain filed and registered on 7 Apr. 2011 with number 1-4467 before the French National Collection of Microorganism Cultures (CNCM) of the Pasteur Institute, and mutant bacteria of the filed strain.