Exploring the composition and function profiles of bacteria from wood- and soil-feeding termites for effective degradation of lignin-based aromatics

Lignocellulosic biomass (LCB) in the form of agricultural, forestry, and agro-industrial wastes is globally generated in large volumes every year. The chemical components of lignocellulosic biomass render them a substrate valuable for biofuel production. However, the rigid association of lignin, cellulose, and hemicellulose component of LCB forms a complex, hierarchical, and recalcitrant structure, which inhibits the solubilization of LCB resources for biofuel production. The learning from termites (wood-feeding and soil-feeding) and further application of their gut bacteria for lignin degradation and bioconversion remain unexplored or at its early stage. With reference to this scientific knowledge gap, this study seeks to highlight the culturable gut bacterial community in soil- and wood-feeding termites, namely Pericapritermes nitobei and Microcerotermes sp., respectively to design a future biorefinery and bioremediation technologies. In this study, a total of 40 and 67 bacterial isolates were indeed identified from Pericapritermes nitobei and Microcerotermes sp., respectively. The identified isolates from both termite species were actually classified into four different phyla: Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes, where the phylum Actinobacteria dominated gut bacteria isolates identified from P. nitobei at 47.5 % while Proteobacteria were dominant in wood-feeding termite, Microcerotermes sp. at 46.27 %. At the genus level, the bacterial isolates enriched from the gut of Microcerotermes sp. belonged to 17 different genera, among which the bacterial genus Streptomyces (28 %) was most prevalent, followed by Enterobacter (11 %). Meanwhile, 9 genera were recorded for gut bacterial isolates from P. nitobei and were dominated by Streptomyces (37.5 %), followed by Acinetobacter (25 %). In general, the gut bacterial symbionts from both termites showed a congruency at the phyla level but were more diverged at a lower classification, inferring that different termite species evolved a unique repertoire of gut bacteria. Moreover, 61 % and 55 % of the gut bacterial isolates from the wood- and soil-feeding termites demonstrated a significant and multifunctional role in the hydrolysis of three lignocellulolytic substrates, including carboxymethyl cellulose, beechwood xylan, and aniline blue dye, indicating their unique functions and assistance to the host for the degradation of lignocellulose or other xenobiotic compounds from soil.