Valorization of crude glycerol by microorganisms: A bibliographic and technological survey

The objective of this review was to investigate the current state of the development of biotechnological routes for the valorization of crude glycerol (CG) using microorganisms, through patent documents and scientific articles. The patents and articles were retrieved through combinations of the code C12N (microorganisms or enzymes), microalgae, and the keyword "crude glycer*". A total of 65 patents and 29 articles directly related to the topic were found. The analysis revealed China's leadership in patent filings and noted that approximately 65 % of the studies utilized bacteria for bioconversion. However, a significant limitation was observed in the diversity of microorganisms explored, with a scarcity of studies focused on bioprospection, especially microalgae and cyanobacteria. Furthermore, studies addressing the use of microalgae-bacteria consortia are rare despite the synergistic potential of these interactions for efficient conversion of crude glycerol into commercially valuable bioproducts. This review directly addresses this gap, emphasizing the benefits associated with the combined use of these microorganisms. The proposal of integrated biorefineries, free of synthetic components and based on the joint use of crude glycerol with other wastewater streams, is also discussed as a promising strategy to overcome technical and economic barriers, promoting the sustainability of the biofuel industry. The reviewed strategies emphasize the need for cost-effective and environmentally responsible processes, focusing on innovation and minimal use of non-renewable resources.