Canola is the major Australian agriculture crop (3 MMT/year for 2022-23). Canolameal constituting ≈40% of total canola seed biomass (w/w), is the major waste product of oil production.
It can be upcycled as prebiotic, synbiotic or a therapeutic agent carrier for animal feed. However, compounds such as glucosinolates, isothiocyanates and sinapins, and their degradation products, attribute unpalatable taste and mild toxicity to the canola meal. Although thermal treatments have shown to be impactful, the heat-labile, high-value compounds in canola meal may get degraded. Gut microbiome of generalised brassica pests have potential to bio-transform these compounds to health beneficial metabolites.
We extracted the gut and frass microbiome from canola feeding caterpillars of Heliothis moth (HP), white cabbage fly (WCF) and cabbage looper (CL). Canola meal was fermented with this microbiome for 1-week. The ferment metabolome was extracted and analysed by LC-MS. Biotransformation efficiency was assessed through assesing short-chained fatty acid elevation, glucosinolate and sinapoyl depletion, and metabolic pathway impact.
Branched-SCFAs such as 2-hydroxy butyrate (7-fold) and 3-hydroxy butyrate (10-fold) showed elevation in HP microbiome ferment, while propionate (8-fold) increased in WCF microbiome ferment. Conversely, gluconapin, aliphatic glucosinolates and sinapoyls showed as 2-fold or higher depletion in the HP and WCF frass ferments. The chemometric analysis showed a presence of ca 654 statistically significant (FDR adjusted p-value ≤ 0.05) metabolites, feeding into 45 significant metabolic pathways. Tryptophan, tyrosine and cysteine and glutathione metabolism pathways were the most impactful pathways across all ferments (Impact > 0.5, FDR adj. p-value ≤ 0.05), indicating the ability of the microbes to convert the toxic compounds to beneficial metabolites.
The study indicates that pest gut microbiota produces considerable biotransformation of agricultural biomass wastes into value-added therapeutic feedstock. Further studies involving integrated multi-omics will aid to isolate the key microbiota, and scale-up the process through precision fermentation.