Abstract

There are abundance of lignite resources in Algeria, particularly in Mitidja plain soils which is known by its fertility and a rapid disappearance of natural organic matters (NOM). The scanning electron microscopy (SEM) morphologies and optical parameters observed for soil humic acids (SHAs) made them different to the commercial ones. Three of the most active strains of 19 actinomycetes were isolated and selected from surface soils at this plain. These strains were identified based on cultural characteristics and chemotaxonomic analysis and classified in the genus Streptomyces. Growth of these strains was assured on a poor liquid medium containing SHAs as carbon and nitrogen sources and degradation occur only in the presence of glucose. A maximal decolorization extent was obtained for 28 days at 30°C under shake culture (67, 66 and 57% for Streptomyces sp. AB1, Streptomycessp. AM2 and Streptomyces sp. AH4, respectively). As compared with initial and final structures of SHAs after incubation (28 days), the structural changes in FTIR spectrum and metabolite products analysed by HPLC indicate the capability of the selected Streptomyces sp. strains to degrade SHAs and to play a part role in lignin degradation and humus turnover in local soils.

Key words: Soil humic acids, Streptomyces, actinomycetes, decolorization, biodegradation.