Abstract

Management of agricultural wastes allows the generation of organic amendments such as compost, whose quality is determined by optimal stabilization and maturation of organic material used for their generation. The decomposition process for producing compost is characterized in four stages according to the temperature reached during the process; Thermophilic stage determines the onset of degradation of recalcitrant compounds and removing mesophilic pathogens; whose efficiency depends on the microbial activity of enriched microorganism from the materials selected for the fertilizer generation. The actinobacterias group is known for its metabolic capacity to synthesize extracellular enzymes capable of degrading lignocelluloses composites, in addition to being characterized as plant growth promoters by production of phytohormones and / or the production of metabolites with antimicrobial activity. So the distribution of community belonging to this group during the composting process provides the opportunity to optimize the composting process and add value to the final product. The aim of this research was to determine the dominant groups’s richness of the actinobacterias community in relation to physic - chemical parameter which affecting the composting process and the actinobacterias community’s structure of the compost original materials. Three rows tumble composting as an open system type were constructed, each representing a replica with a carbon / nitrogen (C / N) ratio equal to 20:1 generated from green grass, oat straw, wheat straw, cow manure and mature compost. Each stage of the composting process were physical - Chemically characterized, considering; moisture, organic matter, organic carbon and total nitrogen. The total bacterial count was determined by epifluorescence microscopy and the actinobacterias’s richness through the study of the V3 region of the 16S ribosomal gene by PCR - DGGE. Bioinformatics cluster analysis of DGGE bands was analyzed using the Multivariate Statistical Package software and 16 S rDNA sequences with the Basic Local Alignment Search Tool. The temporal change of microbial richness and the effect of the variables on it were evaluated by ANOVA and linear correlation coefficients, respectively. Polymorphism pattern associated with the thermophilic stage was significantly different (P <0.05) compared with the other stages of the composting, this change were eventually influenced by temperature. The manure community’s richness had the greater similarity distribution compared to communities from other materials, it was a 65% similarity related with the mesophilic and thermophilic communities. The identities of dominant actinobacterias were related with Streptomyces sp., Nocardia sp., Promicromonospora sp. and Corynebacterium sp. The dominance and richness of the actinobacterias’s community significantly changed in the thermophilic stage. The temperature variable gives the greater contribution in explaining this variation. The actinobacterias’s community from the cow manure could contribute differentially to optimize the composting process highlighting members of the Streptomyces sp.and Promicromonospora sp.