Looking into the world’s largest elephant population in search of ligninolytic microorganisms for biorefineries: a mini-review

Abstract

Gastrointestinal tracts (GIT) of herbivores are lignin-rich environments with the potential to find ligninolytic microorganisms. The occurrence of the microorganisms in herbivore GIT is a well-documented mutualistic relationship where the former benefits from the provision of nutrients and the latter benefits from the microorganism-assisted digestion of their recalcitrant lignin diets. Elephants are one of the largest herbivores that rely on the microbial anaerobic fermentation of their bulky recalcitrant low-quality forage lignocellulosic diet given their inability to break down major components of plant cells. Tapping the potential of these mutualistic associations in the biggest population of elephants in the whole world found in Botswana is attractive in the valorisation of the bulky recalcitrant lignin waste stream generated from the pulp and paper, biofuel, and agro-industries. Despite the massive potential as a feedstock for industrial fermentations, few microorganisms have been commercialised. This review focuses on the potential of microbiota from the gastrointestinal tract and excreta of the worlds’ largest population of elephants of Botswana as a potential source of extremophilic ligninolytic microorganisms. The review further discusses the recalcitrance of lignin, achievements, limitations, and challenges with its biological depolymerisation. Methods of isolation of microorganisms from elephant dung and their improvement as industrial strains are further highlighted.

Yeast–insect interactions in southern Africa: Tapping the diversity of yeasts for modern bioprocessing

“…The ecosystems are affected by geology, geomorphology, and climate which have a direct impact on the flora and, consequently, the fauna, including insects and their associated yeasts symbionts (Scholes & Biggs, 2004). Furthermore, studies on herbivorous mammals including elephants and rhinos and associated insects such as dung beetles within the region report a wide diversity of microbiota (Nwaefuna, Boekhout, et al, 2023; Rammala & Zhou, 2022). Since yeasts thrive in exudates from leaves, roots, flowers, and tree trunks (Cadete et al, 2014; Starmer & Lachance, 2011), the diversity of ecosystems in southern Africa predicts the presence of many novel yeasts.…”

A metagenomic survey of the fecal microbiome of the African savanna elephant (Loxodonta africana)

“…African elephants are hindgut, colonic fermenters and subsist on a diet of mainly grass and the twigs, leaves and fruits of trees and shrubs in their grazing area (Buss, 1961; Greene et al., 2019). Their mechanism of feeding, that is, the fermentation of raw plant materials with the aid of gut microbiota, has sparked interest from a biotechnological perspective, as environmentally sustainable methods for plant material degradation are in demand from industries such as the pulp and paper industry (Rammala & Zhou, 2022).…”

“…Attempts to find sustainable solutions to the degradation of lignocellulytic and pectin biomass have focused on mining the gut and fecal microbiomes of natural digesters such as elephants ( L. africana ), yaks ( Bos grunniens ) and cows ( Bos indicus ) for potential microbes and CAZymes (Gong et al., 2020; Khatoon et al., 2022; Rammala & Zhou, 2022). Indeed, the mining of an 18‐year‐old Asian elephant's metagenome showed that its fecal metagenome was geared toward biomass degradation and in particular carbohydrate degradation with the identification of 11 novel GH families (Jakeer et al., 2020).…”

“…African elephants are hindgut, colonic fermenters and subsist on a diet of mainly grass and the twigs, leaves and fruits of trees and shrubs in their grazing area (Buss, 1961;Greene et al, 2019). Their mechanism of feeding, that is, the fermentation of raw plant materials with the aid of gut microbiota, has sparked interest from a biotechnological perspective, as environmentally sustainable methods for plant material degradation are in demand from industries such as the pulp and paper industry (Rammala & Zhou, 2022).The main constituents of plant material consumed by the African elephant are lignocellulose and pectin. Lignocellulose is a complex material that consists of cellulose, hemicellulose and lignin and is commonly found in plant cell walls, while pectin is a complex…”