Mixed glycerol and orange peel-based substrate for fed-batch microbial biodiesel production

Area of Science:

• Biotechnology
• Microbial Fermentation
• Biorefining

Background:

• Orange peel waste (OPW) is a massive annual byproduct of the juice industry.
• Orange peel extract (OPE) is a carbohydrate-rich liquid derived from OPW.
• Glycerol, a biodiesel byproduct, can enhance microbial lipid production when combined with carbohydrates.

Purpose of the Study:

• To screen oleaginous yeast strains for lipid production using OPE and glycerol.
• To evaluate fed-batch strategies for enhanced lipid production in R. toruloides.
• To assess the feasibility of using OPE as a sustainable feedstock for microbial lipids.

Main Methods:

• Screening of 15 oleaginous yeast strains on OPE- and glycerol-based media.
• Process transfer to a stirred tank reactor (STR) using single-stage feeding fed-batch (SSF-FB) and double-stage feeding fed-batch (DSF-FB) strategies.
• Continuous substrate feeding at low dilution rates post-exponential growth phase.

Main Results:

• R. toruloides NRRL 1091 was selected for fed-batch cultivation.
• SSF-FB process achieved a lipid volumetric production (LVP) of 20.6 g L^-1 with a lipid yield on biomass (Y_L/X) of 0.80.
• Fatty acid profiles of produced lipids were similar to Jatropha oil, a biodiesel feedstock.

Conclusions:

• Orange peel extract (OPE) is a viable and sustainable carbon source for microbial lipid production.
• Fed-batch cultivation strategies, particularly SSF-FB, significantly enhance biomass and lipid accumulation in R. toruloides.
• This process offers a promising avenue for valorizing orange peel waste within a biorefinery framework.