Termite digestomes as sources for novel lignocellulases

Abstract

For most animals, lignocellulose is a nutritionally poor food source that is highly resistant to enteric degradation. Termites, however, have the unique ability to digest lignocellulose with high effi ciency, often using it as a sole food source. Another interesting aspect of termite biology is their symbiotic associations with prokaryotic and eukaryotic gut symbionts. Termite symbionts contribute to lignocellulose digestion effi ciency, but by no means are they responsible for 100% of lignocellulose digestion in the termite gut. The termite digestome can be defi ned as the pool of genes, both termite and symbiont, that contribute to lignocellulose depolymerization and digestion, as well as simple sugar fermentation, nutrient transport, and nutrient assimilation. A central goal of termite digestomics research is to defi ne/understand the relative contributions of termite and symbiont gene products to collaborative lignocellulose digestion. While effi cient microbial cellulases have already been identifi ed and are presently being used in industrial applications, effi cient and inexpensive pre-treatments for lignin and hemicellulose depolymerizationare not yet well developed. In this respect, termite digestomics has already offered signifi cant insights, and can continue to identify relevant enzymes, as well as reveal how to optimally combine and utilize these enzymes for maximum synergy. The topics covered in this review are as follows: lignocellulose structure with emphasis on its potential for depolymerization by termite and gut endosymbiont-derived digestive enzymes; termite biology and ecology from the perspectives of termite nutrition, gut physiology, and lignocellulose digestion; and trends identifi ed through recent termite digestomics research.

Determination of the major compounds in the extract of the subterranean termite Macrotermes gilvus Hagen digestive tract by GC-MS method

“…J., 2017 its abundance and its consumption of woody materials, it is an especially destructive and costly species of termite. Nevertheless, their digestion process in utilizing the wooden structures is interesting, especially in the context of the biofuels and biomate rials industries [8,9]. The unique digestive system of termites features digestive tract enzymes as well as microfauna symbionts.…”

“…The salivary glands are located in the foregut, which leads to the midgut as the junction between the foregut and hindgut. The hindgut is the major region of the digestive system and the site where the symbionts live [9]. The host and symbiont fractions in the termite digestive tract are working together to digest woody materials [14].…”

“…The two-tiered system makes the termite digestion process complex and difficult to study. The goal of this research was to analyze the chemical properties of the termite gut, where the enzymatic degradation of woody particles results in the depolymerization of lignocellulose and cellulose components [8][9][10]. An additional objective of this research was to use gas chromatography-mass spectrometry (GC-MS) to characterize the biochemical compounds arising from woody plant material degradation in the termite gut.…”

Insect cellulolytic enzymes: Novel sources for degradation of lignocellulosic biomass

“…The termite digestomics research is to define collaborative lignocellulose digestion; i.e., to define how termite and symbiont systems complement one another to achieve efficient lignocellulose digestion. From termite digestomics research, a clearer picture of collaborative lignocellulose digestion has emerged now thus suggesting collaboration among termite-derived genes expressed in the salivary gland/foregut and midgut, and symbiont genes expressed in the hindgut (Tartar et al, 2009, Scharf andTartar, 2008). There is now evidence implicating: (i) lignases, GHF1 β-glucosidases, GHF9 endoglucanases, and GHF43 β-xylosidases in the foregut/salivary gland; (ii) apparent feruloyl esterases in the midgut; and (iii) a rich diversity of at least 17 symbiont derived GHFs in the hindgut (i.e., GHF 2,3,5,7,10,11,16,20,26,30,42,45,47,53,77 and 92).…”

Isolation and identification of cellulolytic bacteria from termites gut (Cryptotermes sp.)

“…Insects have evolved effective strategies to utilize lignocellulosic substrates as sources of energy, which makes them an optimal resource for prospecting for novel cellulolytic enzymes. Extensive efforts have characterized lignocellulose degradation in termites [7][8][9][10].…”