Pulse meal should be a valuable product in the animal feed industry based on its strong nutritional and protein profiles. However, it contains anti-nutritional compounds including phenolics (large and small molecular weight), which must be addressed to increase uptake by the industry. Microbial fermentation is currently used as a strategy to decrease larger molecular weight poly-phenolics, but results in the undesirable accumulation of small mono-phenolics. Here, we investigate cell-free biocatalytic reduction of phenolic content in faba bean (Vicia faba L.) meal. A representative phenolic ring-breaking catechol dioxygenase, Bacillus ligniniphilus L1 catechol 2,3-dioxygenase (BLC23O) was used in this proof-of concept based on its known stability and broad substrate specificity. Initially, large-scale fermentative recombinant production and purification of BLC23O was carried out, with functionality validated by in vitro kinetic analysis. When applied to faba bean meal, BLC23O yielded greatest reductions in phenolic content in a coarse air classified fraction (high carbohydrate), compared to either a fine fraction (high protein) or the original unfractionated meal. However, the upstream hydrolytic release of phenolics from higher molecular weight species (e.g. tannins, or complexes with proteins and carbohydrates) likely remains a rate limiting step, in the absence of other enzymes or microbial fermentation. Consistent with this, when applied to a selection of commercially available purified phenolic compounds, known to occur in faba bean, BLC23O was found to have high activity against monophenolic acids and little if any detectable activity against larger molecular weight compounds. Overall, this study highlights the potential viability of the biocatalytic processing of pulse meals, for optimization of their nutritional and economical value in the animal feed industry.
Graphical Abstract
Pulse meal should be a valuable product in the animal feed industry based on its strong nutritional and protein profiles. However, pulse meal contains anti-nutritional and anti-palatability compounds, including (poly)phenolics (tannic and non-tannic), such that improvements in pulse meal processing are still needed to increase its uptake by the industry. Microbial fermentation is currently used as a strategy to decrease tannin content, but results in the undesirable accumulation of monophenolics. Here we investigate the viability of cell-free biocatalytic reduction of phenolic content in faba bean (Vicia faba) meal. A representative catechol dioxygenase, Bacillus ligniniphilus L1 catechol 2,3-dioxygenase (BLC23O) was used in this proof-of concept based on its known stability and broad substrate specificity. Its amenability to large scale recombinant production was established, and its ongoing stability in complex environments including resuspension in slurries of faba bean meal demonstrated. Reaction results suggest that BLC23O is effective for biocatalytic phenol reduction in faba bean meal. However, the upstream hydrolytic release of phenolics from higher molecular weight species (tannins, proteins, carbohydrates) likely remains a rate limiting step, in the absence of other enzymes or microbial fermentation. Overall, this study highlights the potential viability of the biocatalytic processing of pulse meals, for optimization of their nutritional and economical value in the animal feed industry.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.