Quorum-driven microbial consortium for Bioplastic production from agro-waste

Microbial consortia have high relevance in natural environments. Here we present the production of polyhydroxyalkanoates (PHA) from agro-industrial residues by a synthetic interkingdom consortium formed by the saprotrophic fungus <i>Ophiostoma piceae</i> CECT 20146, which encodes a wide range of lignocellulolytic enzymes, and a natural PHA producer, <i>Pseudomonas putida</i> KT2440. Two agro-industrial residues were utilized: Brewer's Spent Grain (BSG) as a carbon/nitrogen source and biofilm scaffold and waste cooking oil (WCO) as a carbon source for PHA synthesis. Through biochemistry, microscopy, and omics analyses, it is shown that <i>P. putida</i> accumulates up to 40.2% of intracellular PHA when the quorum sensing molecule, farnesol (naturally produced by <i>O. piceae</i>) is added, thanks to the increased proliferation of <i>P. putida</i> cells. An interactive Shiny application has also been developed for an easy visualization and comprehension of all the transcriptomics and metabolomics data: https://jgf-bioinformatics.shinyapps.io/Visualization_app/. These results support the increased PHA production of the consortium by an induction of gene <i>phaG</i>, which redirects intermediaries of the fatty acid biosynthesis to PHA precursors, and the repression of the PHA depolymerase <i>phaZ</i> in <i>P. putida</i>. The trophic interaction between microorganisms seems to rely on the citric acid produced by <i>O. piceae</i> and the glycerol liberated from WCO, which can both be consumed by <i>P. putida</i>. Bioreactor scale-up experiments allowed a 3.3-fold increase in the PHA concentration in the consortium (6.7 g·L^-1) without pretreatment or sterilization of the substrates, laying the groundwork for the implementation of an industrial consolidated bioprocess (CBP).