Biotransformation of Canola Feedstock Waste Using Brassica Pest Microbiome: Proof of Concept for Insects as Bioengineers

The toxicity of glucosinolate, isothiocyanate and sinapin limits canola meal's use as non-ruminant animal feed. While monoculture microbial biorefining has been explored, the potential and capability of insect-associated microbiomes in this context remain underexplored. Herein, we extracted the gut and frass extracts from canola feeding larvae of Heliothis moth (HP), cabbage white (WCF) and cabbage looper (CL). Canola meal was fermented for one week with these extracts, followed by liquid chromatography-mass spectrometry (LC-MS)-assisted metabolomics analysis. Elevated branched-SCFAs 2-hydroxy butyrate and 3-hydroxy butyrate and propionate were observed in HP and WCF ferments, respectively. Aliphatic glucosinolates and sinapins showed ≥2-fold depletion in the HP and WCF frass ferments. In gut extract and frass-fermented canola meal, particularly of the HP group, tryptophan, tyrosine, and cysteine and glutathione metabolism were the most impactful pathways, aiding biogenic amine and branched-SCFA synthesis. S-adenosyl methionine (SAM) led salvaging, playing a key role in amino acid recycling via mercapturate metabolism, oxidative stress handling via the methionine and cysteine metabolism pathway, and sinapin metabolism through syringate degradation. These findings highlight the metabolic mechanism of brassica herbivore insect gut microbiome in detoxifying and adding value to canola meal. Such microbial communities have the potential to upcycle canola meal into a nutrient-rich feed additive with gut-health-promoting properties.