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Abstract
BackgroundLignocellulosic biomass is the most abundant resource on earth. Lignocellulose is mainly composed of cellulose, hemicelluloses, and lignin. The special construction of three kinds of constituents led to the prevention of effective degradation. The goal of this work was to investigate the great potentials of bovine rumen for novel cellulolytic bacterial isolation, which may be used for chemicals and biofuel production from lignocellulose.ResultsA cellulolytic strain, ZH-4, was isolated from Inner Mongolia bovine rumen. This strain was identified as Escherichia coli by morphological, physiological, and biochemical characteristics and 16S rDNA gene sequencing. The extracellular enzyme activity analysis showed that this strain produces extracellular cellulases with an exoglucanase activity of 9.13 IU, an endoglucanase activity of 5.31 IU, and a β-glucosidase activity of 7.27 IU at the pH 6.8. This strain was found to produce 0.36 g/L ethanol and 4.71 mL/g hydrogen from corn straw with cellulose degradation ratio of 14.30% and hemicellulose degradation ratio of 11.39%.ConclusionsIt is the first time that a cellulolytic E. coli was isolated and characterized form the bovine rumen. This provided a great opportunity for researchers to investigate the evolution mechanisms of the microorganisms in the rumen and provided great chance to produce biofuels and chemicals directly from engineered E. coli using consolidated bioprocess.
Highlights
Lignocellulosic biomass is the most abundant resource on earth
Screening of cellulolytic bacteria from bovine rumen The sample was taken from bovine rumen and was enriched in a medium with Whatman filter paper as sole carbon source
The isolated ZH-4 was again detected with respect to their enzyme activity for confirmation of our result. 16S rDNA and genome sequencing analysis confirmed the purity of the isolate and revealed 99% sequence identity with E. coli
Summary
Lignocellulose is mainly composed of cellulose, hemicelluloses, and lignin. The goal of this work was to investigate the great potentials of bovine rumen for novel cellulo‐ lytic bacterial isolation, which may be used for chemicals and biofuel production from lignocellulose. Lignocellulose consists mainly of cellulose (35–50%), hemicellulose (25–30%), and lignin (25–30%) [2]. As the main component of lignocellulose, cellulose is made up of linear chains of 1,4-β-linked glucosyl residues and enwrapped by hemicellulose and lignin, which prevents the effective degradation [3, 4]. Biomass-degrading genes and genomes have been focused to investigate the function and degradation mechanisms of these ruminal cellulolytic microorganisms by metagenomics [18]. A novel encoded bifunctional xylanase/endoglucanase gene, RuCelA, was cloned from the metagenomics library of yak rumen microorganisms [20]. A novel Clostridiaceae (AN-C16-KBRB) with bifunctional endo-/exo-type cellulase was isolated from the bovine rumen at Jeongeup in Korea, while Treponema JC4 was isolated from bovine rumen in the semiarid tropics of Australian [23, 24]
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