Biodegradation of Lignocellulosic Waste by Enriched Environmental Microbial Sources and Sequential Fermentation by Saccharomyces Cerevisiae

Abstract

The increasing global demand for energy and the rapid depletion of fossil fuels have led to the search for alternative energy sources. Bioethanol is one option that can be produced from lignocellulose materials, which involves their biodegradation and fermentation. This study investigated the degradation of three lignocellulose waste materials by enriched microbial communities from three environmental sources andtheir sequential fermentation by Saccharomyces cerevisiae. The NaOH-pretreated lignocellulose substrates in a basal medium were inoculated with enriched microbial suspensions and incubated at room temperature. The extent of biodegradation was determined after 5 days of incubation by the gravimetric method. The bioethanol content was estimated by the solvent extraction & dichromate oxidation method after incubating another 3 days with S. cerevisiae. Both the extent of biodegradation and ethanol yield differed significantly among the different lignocellulose-microbial source combinations (p<0.05). The highest biodegradation (80.95%) was found in grass clippings by cow dung microbial consortium, while the lowest degradationwas in palmyra by compost consortium (19.46%). The ethanol yield ranged from 1.24 to 1.87% (V/V) substrate, which was comparable to reported values from similar studies, but it did not correlate with the extent of lignocellulose degradation (r = 0.0378 and P = 0.923). This could be either because microbial consortia, though they are good degraders they are poor saccharifiers, or the fermentation would have been limited by broth conditions. Microbial consortia with high lignocellulose-degrading potential may be formulated from natural microbial sources, but their contribution to ethanol production needs further studies.