Research

1. Engineering and Analyzing Cyanobacterial Metabolism for Sustainable Biochemical Production

Cyanobacteria are prokaryotic photoautotrophic organisms which can be engineered to produce valuable biochemicals sustainably. Currently, amino acid production uses petroleum derived feedstocks or fermentation processes that rely on agriculture for sugars. On the other hand, cyanobacteria can be engineered to produce amino acids and other valuable biochemicals by utilizing photosynthesis to convert freely available sunlight and carbon dioxide.

• Our lab is interested in the development of cyanobacteria for amino acid overproduction using random mutagenesis and metabolic engineering strategies. Recently, we combined metabolic engineering and random mutagenesis strategies for overproduction of tryptophan (Deshpande et al., 2020) .Current work involves using recently discovered fast growing strains for production of essential amino acids.

• One of the bottlenecks in development of strains with high productivity is improving photosynthesis and carbon fixation. This is only feasible with an advanced understanding of these processes under different environmental conditions and genetic backgrounds. To address this problem, our lab uses a "multi-omics" approaches including Fluxomics (Metabolic Flux Analysis) and Proteomics to provide a systems level understanding which can be used to guide strain engineering. Recently, we have combined fluxomic and proteomic measurements to unravel regulation of the Calvin-Benson-Bassham cycle (Yu King Hing et al., 2019)

2. Mathematical Modeling of Transport of Volatile Organic Compounds in Plants

Although there are different biosynthetic sites and ways of emission, volatile organic compounds (VOCs) must all move across the plasma membranes, the aqueous cell wall, and sometimes the cuticle to exit the plant cell. Progress has been made in understanding plant volatile biosynthesis, but their release from the cell remains less understood.

• Our mathematical model has predicted that VOCs will accumulate in membranes if they passively diffuse into subsequent cellular layers at a physiologically relevant rate. Due to their high octanol-water partition coefficients, VOCs favorably partition into the hydrophobic lipid bilayer and the cuticle, making their diffusion into aqueous compartments slow. Hence, biological mechanisms are required to maintain VOC concentration in cellular membranes with observed steady-state emission rates. (Widhalm et al., 2015)

• We have proved that adenosine triphosphate-binding cassette (ABC) transporters can involve in the export of not only waxes but also VOCs across the plasma membranes. (Adebesin et al., 2017)

• Recently, we identified that cuticle not only serves as an outermost layer that protects the cell but also acts as a sink/concentrator for VOCs and hence preventing the potentially toxic internal accumulation of these hydrophobic compounds. (Liao et al., 2021)

As the thickest layer among the three subcellular barriers, the cell wall should act as a large barrier for the VOCs to simply diffuse through. Now, we are working on the remained puzzle in this mass transport procedure: how do VOCs pass through the aqueous cell wall?