Use of polyamino acid derivatives as preserving agents, compositions comprising them and preserving process using them

A process for preserving a composition comprising:

• introducing into said composition at least one preserving agent chosen from polyamino acid derivatives of formula (I) and salts thereof,
• in which:
• X is chosen from O, S, NH and NR″, wherein R″ is chosen from saturated and unsaturated, linear and branched C1-6 hydrocarbon-based radicals;
• R1 is chosen from:
• (i) linear and branched, saturated and unsaturated C1-40 hydrocarbon-based radicals;
• (ii) radicals of the formula
• wherein s is a number chosen from 0, 1, 2, 3 and 4;
• and R4 is chosen from hydrogen and radicals chosen from —NH2, —OH, —SH, —CHOHCH3, —CONH2, —NH—C(NH2)═NH, —C6H5, —C6H4OH and
• (iii) radicals of the formula
• wherein m is a number chosen from 3, 4 and 5;
• R2 is chosen from hydrogen;
• saturated and unsaturated, linear and branched C1-8 hydrocarbon-based radicals;
• and radicals chosen from —CH2C6H5, —CH2C6H4OH, —CH2OH, —CHOHCH3, —(CH2)t—NH2, wherein t is a number chosen from 3 and 5;
• R3 is chosen from hydrogen and saturated and unsaturated, linear and branched C1-6 hydrocarbon-based radicals;
• and
• n is a number greater than 1 chosen such that the number average molecular weight of the polyamino acid derivative ranges from 100 to 200 000;
• wherein the repeating unit may be identical or different for the same derivative.