Microbial Bioprocess for Extracellular Squalene Production and Formulation of Nanoemulsions

Sustainable production of natural
resources requires a clean manufacturing
process with clean raw materials due to the risk of environmental
contaminations. Microbial cell factories have enabled the production
of natural products including hydrophobic chemicals. However, the
microbial cells limit the production titer because of the limited
intracellular storage capacity and no transport across the cell membrane.
Herein, we engineered Corynebacterium glutamicum to produce hydrophobic squalene as a model product. Notably, squalene
was secreted in the defined culture medium without in situ extractions.
As a result, the secreted squalene was related to the glycolipid association
with synthesized squalene in the cell envelope and a facilitated secretion
occurred during cell division. Protein engineering and pathway engineering
of C. glutamicum enhanced the total
squalene (tSQ) production, where fed-batch fermentation resulted in
1406 ± 16 mg/L tSQ production (32% tSQ in the medium). Promoting
extraction with dodecane overlay, bio-squalene nanoemulsions were
formulated and the creaming effects were analyzed for cosmetic application.
Combining metabolic pathway engineering and facilitated secretion
in microbial cells will be a good strategy to produce sustainable
hydrophobic chemicals.