Abstract
The effective fermentation of xylose remains an intractable challenge in bioethanol industry. The relevant xylanase enzyme is also in a high demand from industry for several biotechnological applications that inevitably in recent times led to many efforts for screening some novel microorganisms for better xylanase production and fermentation performance. Recently, it seems that wood-feeding termites can truly be considered as highly efficient natural bioreactors. The highly specialized gut systems of such insects are not yet fully realized, particularly, in xylose fermentation and xylanase production to advance industrial bioethanol technology as well as industrial applications of xylanases. A total of 92 strains from 18 yeast species were successfully isolated and identified from the gut of wood-feeding termite, Reticulitermes chinensis. Of these yeasts and strains, seven were identified for new species: Candida gotoi, Candida pseudorhagii, Hamamotoa lignophila, Meyerozyma guilliermondii, Sugiyamaella sp.1, Sugiyamaella sp. 2, and Sugiyamaella sp.3. Based on the phylogenetic and phenotypic characterization, the type strain of C. pseudorhagii sp. nov., which was originally designated strain SSA-1542T, was the most frequently occurred yeast from termite gut samples, showed the highly xylanolytic activity as well as D-xylose fermentation. The highest xylanase activity was recorded as 1.73 and 0.98 U/mL with xylan or D-xylose substrate, respectively, from SSA-1542T. Among xylanase-producing yeasts, four novel species were identified as D-xylose-fermenting yeasts, where the yeast, C. pseudorhagii SSA-1542T, showed the highest ethanol yield (0.31 g/g), ethanol productivity (0.31 g/L·h), and its fermentation efficiency (60.7%) in 48 h. Clearly, the symbiotic yeasts isolated from termite guts have demonstrated a competitive capability to produce xylanase and ferment xylose, suggesting that the wood-feeding termite gut is a promising reservoir for novel xylanases-producing and xylose-fermenting yeasts that are potentially valued for biorefinery industry.
Highlights
Wood-feeding termites, a gold mine of science and plague of buildings, are the most impressive and effective wood-decomposing systems on the earth in terms of their processing efficiency and scales [1]
Several studies have further shown an astonishing biodiversity in termite gut symbionts for most wood-feeding lower termites, such as in the genus of Reticulitermes; and these gut symbionts are primarily represented by prokaryotes and eukaryotes, including fungi, notably yeasts, and flagellated protozoa being classified in eukaryote category [8]
Lignocellulosic processes in xylophagous insects, such as wood-feeding termites, are considered to be a very efficient biodegradation reaction that is said to be largely due to a significant contribution from a variety of gut symbionts, including the yeasts
Summary
Wood-feeding termites (order: Isoptera), a gold mine of science and plague of buildings, are the most impressive and effective wood-decomposing systems on the earth in terms of their processing efficiency and scales [1]. Termites harbor more than 200 symbiotic microbial species that produce an array of cellulosic and hemicellulosic degrading enzymes to digest cellulose and hemicellulose components of the wood. These enzymes, in turn, have a potential value for the bio-ethanol production from lignocellulosic biomass in the biorefinery industries [2]. Several studies have further shown an astonishing biodiversity in termite gut symbionts for most wood-feeding lower termites, such as in the genus of Reticulitermes; and these gut symbionts are primarily represented by prokaryotes and eukaryotes, including fungi, notably yeasts, and flagellated protozoa being classified in eukaryote category [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
