PLFAs of the microbial communities in composting mixtures of agro-industry sludge with different proportions of household waste

摘要

Phospholipid fatty acids (PLFAs) were analysed at different time periods during composting of two waste mixtures rich in fats M1 (22%) and M2 (39%) with the aim of monitoring changes in microbial community structure The two mixtures consisted of a sludge sample collected from a vegetable oil refinery effluent treatment plant combined with household wastes The PLFA profiles of both mixtures revealed that at the start of the process fungi and Gram-negative bacteria (G-) were more abundant in M2 than in M1 During the thermophilic phase branched PLFA (i15 0 a15 0 i16 0 and i17 0) markers of Gram-positive bacteria (G+) became more abundant in M1 while G- bacteria were predominant in M2 The PLFA profiles in M1 representing non-specific G+ and G- bacteria as well as fungi decreased during the cooling phase (maturation) while an increase was recorded in M2 which was richer in fats The Shannon-Weaver diversity Index (Ish) showed a greater Increase during M1 composting (from 0 69 to 1 05) mainly for G+ bacteria and G- bacteria than in M2 composting (from 0 79 to 0 84) Principal components and cluster analyses revealed a succession of different communities during composting which varied from fungi and G- bacteria to G+ and thermophilic and thermotolerant G- bacteria The end of composting was characterized by a reduction of all these microbial entities especially for M1 except actinomycetes which are associated with compost stability