Date of Award

2024

Document Type

Thesis

Abstract

Edible insects are increasingly recognized as a solution to several problems faced by mankind, including hunger, malnutrition and microbial infections. Additionally, the gut symbionts of insects, along with their associated metabolites and enzymes, hold promising potential for industrial and pharmaceutical applications. However, the detailed nutritional properties, gut microbiota, and microbial secondary metabolites associated with the gut symbionts of various insects, including wood-boring beetles, have not yet been comprehensively reported. In this current study, the nutritional properties, and the characteristics of the gut microbiota of two wood-boring species (Titocerus jaspideus and Passalus punctiger) collected from two indigenous forested areas was investigated. Further, Rubasperone B was isolated in a bioactivity guided protocol from an Aspergillus niger gut symbiont of P. punctiger. Nutritional profiles were determined using liquid and gas chromatography techniques (LC-MS and GC-MS), and UV-Vis spectrometry. Exploration of gut symbionts was carried out through metagenomic sequencing of various gene regions, while metabolite isolation and structure elucidation was achieved using chromatography and mass spectrometry and Nuclear Magnetic Resonance (NMR) experiments, respectively. The extract’s antibacterial activities were determined utilizing Kirby disc diffusion assay. The crude protein content of the beetle larvae ranged between 27.5 - 39.8 mg BSA/g. Cereal limiting amino acids such as lysine (7.9-9.9 mg/g), methionine (0.48-0.64 mg/g) and threonine (2.31-2.55 mg/g) were considerably high in the larvae. Methyl-5Z,8Z,11Z,14Z-eicosatetraenoate and methyl-9Z-octadecenoate were predominant polyunsaturated and monounsaturated fatty acids, respectively. High total phenols (>4.4 mg GAE/g), flavonoids (>3.6 mg QE/g) and anti-oxidative activities (>67%) were recorded for both larvae. Over 50% of Amplicon Sequence Variants (ASVs) constituted of Firmicutes in T. jaspideus. The dominant phyla in both beetle species were Bacteroidota (4.20% to 19.79%) and Proteobacteria (15.10% to 23.90%). Lactococcus lactis was the most abundant and core prokaryote in the guts of T. jaspideus. The fungi identified in the guts of the two insects belonged to the phylum Obazoa (66%) and Ascomycota (>15%). Scheffersomyeces. sp was the core eukaryote recorded. The diversity of gut microbiota in both insect species did not vary significantly. Most of the prokaryotic genes expressed were predominantly associated with biosynthesis and metabolism. However, from a culture of Aspergillus niger, the most bioactive fungus, 5,5′-dihydroxy-6,6′,8,8′-tetramethoxy-2,2′-dimethyl[9,10′-bi-4H-naphtho[2,3-b]pyran]-4,4′-dione (Rubasperone B) was isolated from ethyl acetate fraction. The structure elucidation was achieved by extensive analysis of 1D and 2D NMR spectra, and LC-MS data. This molecule exhibited notable antibacterial activity against test pathogens, with MIC and MBC values ranging from 93.8 – 375.5 μg/mL and 187.5 – 375.0 μg/mL, respectively. This study is significant in unravelling the nutritional properties and uncovering the antibacterial properties of gut microbiota from wood boring beetles. The findings can be applicable in pharmaceutical and food industries.

Download

Share

COinS