Advances in circular biorefinery processes towards organic acids from crude glycerol by microbial cell factories

Abstract

Organic acids are highly demanded products synthesized by petrochemicals or microbial cell factories (MCFs) using various carbon feedstocks. MCFs are bioengineered microbes depicted to transform different carbon sources into industrially relevant, value-added products. Utilizing oil waste CG as a carbon feedstock for MCFs to produce organic acids at a large scale has emerged as a cutting-edge alternative to traditional chemical processes. This review details the major organic acids produced from CG by MCFs, revealing life cycle analysis (LCA) and techno-economic assessment (TEA) of cradle-to-gate circular economy-based bioprocesses. Among all microbes, Yarrowia lipolytica synthesizes a higher variety of organic acids from CG that can be explored at industrial standards on the bioreactor scale. Due to the substrate toxicity of CG, fed-batch and repeated batch fermentation approaches are prominent for increasing CG uptake by microbes to produce organic acids. Recent advances, including metabolic engineering, metabolic flux analysis (MFA), systems biology, and mathematical modeling tools, are also employed to enhance the titer, yield, and productivity of microbial organic acids from CG through sustainable, eco-friendly, and energy-efficient routes under mild reaction conditions. Therefore, the inexpensive renewable feedstock CG can be utilized for organic acids by MCFs in future circular biorefineries at pilot scales.