Nanoparticle-assisted growth of algae for application in the production of biofuels and other specialty products

Abstract

In recent years, algae have proven to be a promising source of biofuel and other specialty products. Unlike typical crops used in biofuel production, algae do not require the land or freshwater resources typically used to produce biofuels. However, algae fuel is still not commercially viable, in large part due to the difficulty in growing large-scale, high-density algae cultures quickly. In this thesis, I aim to address the problem of the lack of commercial viability of algae-based biofuels from two angles: by attempting to improve the growth rate of a marine algae through the introduction of nanoparticles containing fluorescent red dye and by laying the groundwork for a novel method of transforming yeast and algae spheroplasts by introducing plasmids encapsulated in cationic polymer. In my preliminary screenings of various nanoparticle formulations, I identified nanoparticles stabilized by hydroxypropyl methylcellulose (HPMC) and containing a polycaprolactone (PCL) with a dye loading of 2wt% of either Nile red (NR) or Perylene red (PR) as good candidates for introduction into the photobioreactors. After settling on the formulation, the reactors were treated with 10mg/L of HPMC/PCL nanoparticles loaded with 2wt% NR; this run displayed slightly worse growth than those grown without nanoparticles, implying that perhaps these particles or the dye itself may have a slight toxicity. I then investigated whether the time of addition of the nanoparticles (lag phase vs growth phase) would have an effect on the growth rate and overall biomass produced, as I suspected that acute toxicity might have a greater effect on an immature culture. The algae that was never exposed to any nanoparticle achieved the highest cell density, implying that perhaps the nanoparticles were somewhat toxic to the algae. I suspect that the source of toxicity is NR leaching out of the nanoparticles and interacting with the algae cells. To investigate this, I am currently conducting two triplicate runs of reactors treated with 10mg/L of blank HPMC/PCL nanoparticles and nanoparticles loaded with 2wt% PR. From the preliminary results, it appears that neither of these two formulations result in a decreased slope or elongated lag phase (as was observed with NR-containing particles). Thus, it appears that PR-containing nanoparticles might be better candidates for improving algae growth rate than their NR-containing counterparts. Additionally, in this thesis, I laid the ground work for testing a new method of transformation using cationic polymers (as opposed to harsher methods like electroporation and biolistic) to deliver a plasmid to the target yeast or algae cell.