Agricultural and food wastes are a promising renewable, low-cost feedstock for bioproduction of
value-added compounds. Creating a consolidated bioprocess using these complex substrates
in a single microorganism is limited by metabolic burden; the overexpression of heterologous
genes redirects endogenous resources from essential processes, thus reducing the growth and
productivity of the cell. Microbial consortia, employing division of labour (DOL) between cells,
can mitigate this burden and achieve waste utilisation beyond that attainable in monocultures.
In this thesis I investigate the use of DOL in consortia for the degradation of plant-derived
polysaccharides by Yarrowia lipolytica, a promising host for a range of biotechnological
applications.

Firstly, I explore the relationship between expression, secretion and metabolic burden. I design
and engineer a 2-strain consortium for the degradation of starch, with one strain expressing
α-amylase and the other expressing glucoamylase. I model this system and identify in silico a
threshold of expression above which DOL delivers faster growth compared to a monoculture
co-expressing both amylases. In vivo I identify Y. lipolytica consortia which can achieve higher
growth rates than their equivalent monoculture on starch as the sole carbon source. The
performance of these starch-degrading consortia is determined by the strongest amylase strain.

Secondly, I explore how designing different relationships between the two cells in a consortium
alters their behaviour compared to monoculture. I design and engineer 2-strain consortia with
one strain expressing α-amylase, for starch degradation, and the other expressing xylanase for
xylan degradation. Here, I use the substrate specificities for glucose and xylose to create
different population dynamics between the two cells. I observe that the generalist consumer DOL
strategy, where both cells can consume both glucose and xylose, provides the greatest growth
advantage over a monoculture equivalent and achieves a 14.11% increase in β-carotene
production compared to the monoculture strategy.