Overmans, S. J. | Search bioRxiv

bioRxiv2023

Comparison of alternative solvents for in situ extraction of hydrocarbons from the colonial green alga Botryococcus braunii race B (Showa)

The colony-forming, green microalga Botryococcus braunii secretes petroleum-like hydrocarbons, which enables the non-destructive continuous in situ extraction, milking, of these extracellular products during culture growth without cell lysis. This work compares the suitability of 15 different solvents, including alkanes, halogenated solvents, and green solvents, for in situ extraction of B. braunii race B (Showa strain) hydrocarbons after acclimation to moderate salinity stress. After 24 h of extraction, bio-based terpene green solvents such as {gamma}-terpinene showed the highest hydrocarbon recovery, around 10-fold greater than with conventional alkane solvents. Brominated alkanes and liquid perfluorocarbons (FCs) formed a lower phase to algal cultures rather than an upper phase as with other solvents, but only bromodecane effectively captured extracellular hydrocarbons similar to conventional alkane solvents. However, bromodecane and all green solvents were too toxic for two-phase continuous culture contact hydrocarbon milking, leading to 33-100% chlorophyll content loss. To overcome the biologically adverse effects of these solvents with suitable hydrocarbon recovery, future research should focus on their application in short-term extraction period milking systems to minimize algal-solvent contact and enable continuous extraction. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=98 SRC="FIGDIR/small/563540v2_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@1072e6borg.highwire.dtl.DTLVardef@787c8forg.highwire.dtl.DTLVardef@39af4dorg.highwire.dtl.DTLVardef@123ed79_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

biochemistry↗

bioRxiv2022

Continuous extraction and concentration of secreted metabolites from engineered microbes using membrane technology

Microalgal cultivation in photobioreactors and membrane separations are both considered sustainable processes. Here we explore their synergistic combination to extract and concentrate a heterologous sesquiterpenoid produced by engineered green algal cells. A hydrophobic hollow-fiber membrane contactor was used to allow interaction of culture broth and cells with a dodecane solvent phase to accumulate algal produced patchoulol. Subsequent continuous membrane extraction of patchoulol from dodecane enabled product concentration in a methanol stream as well as dodecane recovery for its reuse. A structure-based prediction using machine learning was used to model a process whereby 100% patchoulol recovery from dodecane could be achieved with solvent-resistant nanofiltration membranes. Solvent consumption, E-factor, and economic sustainability were assessed and compared with existing patchoulol production processes. Our extraction and product purification process offers six- and two-orders of magnitude lower solvent consumption compared to synthetic production and thermal-based separation, respectively. Our proposed methodology is transferable to other microbial systems for the isolation of high-value isoprenoid and hydrocarbon products.

bioengineering↗