A Biological OR(XNOR) Logic Gate Couples Carbon Source and Transgene Expression Switching in a Komagataella phaffii (Pichia pastoris) Strain Co-producing Process-Enhancing Lipase and a Virus-like Particle (VLP) Vaccine.

We constructed a three-input biological logic gate: S OR (G XNOR M), where S is sorbitol, G is glycerol, and M is methanol, to optimize co-expression of two transgenes in Komagataella phaffii using batch-mode carbon source switching (CSS). K. phaffii was engineered to harbor transgenes encoding a Candida rugosa triacylglycerol lipase, which can enhance downstream processing by removing host cell lipids from homogenates, and the hepatitis B virus surface antigen (HBsAg), a protein that self-assembles into a virus-like particle (VLP) vaccine. Using the native alcohol oxidase 1 (PAOX1) and enolase 1 (PENO1) promoters to direct VLP vaccine and lipase expression, respectively, successfully provided an OR(XNOR) gate function with double-repression as the output. This logic gate functionality enabled use of CSS to ensure that approximately 80% of total VLP yield was accumulated before cells were burdened with lipase expression in 250 mL DasGip bioreactor cultivation.

Synthetic biology tools for engineering Goodwin oscillation in Trypanosoma brucei brucei.

Kinetoplastid protozoa possess properties that are highly divergent from the mammalian, yeast and bacterial cells more commonly used in synthetic biology and represent a tantalisingly untapped source of bioengineering potential. Trypanosoma brucei brucei (T. b. brucei), an established model organism for studying the Kinetoplastida, is non-pathogenic to humans and provides an interesting test case for establishing synthetic biology in this phylogenetic class. To demonstrate further the tractability of Kinetoplastida to synthetic biology, we sought to construct and demonstrate a Goodwin oscillator, the simplest oscillatory gene network, in T. b. brucei for the first time. We report one completed iteration of the archetypal synthetic biology Design-Build-Test-Learn (DBTL) cycle; firstly, using Ab initio mathematical modelling of the behaviour a theoretical, oscillatory, trypanosomal synthetic gene network (SGN) to inform the design of a plasmid encoding that network. Once assembled, the plasmid was then used to generate a stable transfectant T. b. brucei cell line. To test the performance of the oscillatory SGN, a novel experimental setup was established to capture images of the fluorescent signal from motion-restricted live cells. Data captured were consistent with oscillatory behaviour of the SGN, with cellular fluorescence observed to oscillate with a period of 50 min, with varying amplitude and linear growth trend. This first DBTL cycle establishes a foundation for future cycles in which the SGN design and experimental monitoring setup can be further refined.