Lignin Biodegradation with Ligninolytic Bacterial Strain and Comparison of Bacillus subtilis and Bacillus sp. Isolated from Egyptian Soil

摘要

Lignin is the most abundant aromatic polymer in nature. It is synthesized by higher plants, reaching levels of 20-30% of the dry weight of woody tissue, next to cellulose, is the second most abundant compound in plant biomass and a partial decay of lignin provides numerous aromatic monomers such as ferulic and vanillic acids. These aromatic compounds have attracted attention as renewable resources for the production of chemicals traditionally derived from petroleum. An Isolation and identification environmental friendly bacteria for lignin degradation becomes an essential, because all the previous researches concentrated on using fungal treatments. The importance of ligninolytic bacteria raised, because lignin-degrading bacteria have wider toleranceof temperature, pH and oxygen limitation than fungi. In addition, the application of fungi in bioleaching of raw pulp is not feasible due to its structural hindrance caused by fungal filament. One bacterial strain isolated from Egyptian soil in Kafr El-Dawar (latitude 31.1397 and longitude 30.1292) area was molecularly and physiologically identified. Potential aerobic bacterial strains KafAH19 was found capable to effectively degrade synthetic lignin (lignin Alkali) and utilize it as a sole carbon source. Further, this potential strain (KafAH19) was biochemically characterized as Gram-positive rod. Subsequently, partial sequence of 16S rDNA identified these strains as Bacillus sp. (EU978470). In batch 6 days degradation experiments this strain utilized lignin as a sole carbon source and achieved maximum lignin degradation on the sixth day at pH 6 (81.4%), however the lowest lignin degradation rate was observed at pH 13 (34.2%) at the end of the incubation time.