Abstract
As a strategy to find efficient lignocellulose degrading enzymes/microorganisms for sugarcane biomass pretreatment purposes, 118 culturable bacterial strains were isolated from intestines of sugarcane-fed larvae of the moth Diatraea saccharalis. All strains were tested for cellulolytic activity using soluble carboxymethyl cellulose (CMC) degrading assays or by growing bacteria on sugarcane biomass as sole carbon sources. Out of the 118 strains isolated thirty eight were found to possess cellulose degrading activity and phylogenetic studies of the 16S rDNA sequence revealed that all cellulolytic strains belonged to the phyla γ-Proteobacteria, Actinobacteria and Firmicutes. Within the three phyla, species belonging to five different genera were identified (Klebsiella, Stenotrophomonas, Microbacterium, Bacillus and Enterococcus). Bacterial growth on sugarcane biomass as well as extracellular endo-glucanase activity induced on soluble cellulose was found to be highest in species belonging to genera Bacillus and Klebsiella. Good cellulolytic activity correlated with high extracellular protein concentrations. In addition, scanning microscopy studies revealed attachment of cellulolytic strains to different sugarcane substrates. The results of this study indicate the possibility to find efficient cellulose degrading enzymes and microorganisms from intestines of insect larvae feeding on sugarcane and their possible application in industrial processing of sugarcane biomass such as second generation biofuel production.
Highlights
The imminent need to replace fossil-based transport fuels with more environment-friendly renewable alternatives, has sparked an increasing interest in finding abundant and cheap resources for biofuel production
Bacterial taxonomy and sequencing analysis of the 16S rDNA gene In vitro DNA amplification by the polymerase chain reaction (PCR) of the entire 16S rDNA gene sequence was performed using genomic DNA isolated from the 38 bacterial strains showing cellulolytic activity as a template
Out of a total number of 118 cultivable bacterial isolates obtained from intestines of sugarcane-fed D. saccharalis, one third (38) were found to possess cellulolytic activity as determined by degradation of carboxymethyl cellulose (CMC)
Summary
The imminent need to replace fossil-based transport fuels with more environment-friendly renewable alternatives, has sparked an increasing interest in finding abundant and cheap resources for biofuel production. Especially in the form of plant cell wall material, is a renewable, abundant and relatively cheap mixture of organic materials, principally containing polysaccharides (~75% dry weight) and lignin (~25% dry weight). Lignin on the other hand, is formed by a noncarbohydrate complex structure built from phenylpropanoid units. This phenolic polymer sticks to the polysaccharide components, strengthening the whole structure which renders it extremely resistant to biological degradation (Cheng and Wang 2013)
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