(529d) Enhancing Microbial Fermentations for Sustainable Compound Production: Case Studies on Fatty Alcohols and Citramalate

The field of synthetic biology has unveiled promising opportunities for the development of engineered microbes capable of sustainable production of compounds of interest. However, the translation of engineered strains into commercial success remains a challenge. Scale-up of microbial fermentations is particularly daunting, as reproducibility issues arise from heterogeneity in bioreactors and proprietary variations in fermentation conditions. A crucial aspect of aerobic fermentation is the air feeding rate, which varies across different fermentations and significantly impacts production outcomes. Our study delves into the investigation of oxygen mass transfer as an invaluable tool for optimizing fermentations. Two case studies are presented: one involving the use of a Taylor-Couette bioreactor for fatty alcohol production by Yarrowia lipolytica, and the other utilizing a traditional bioreactor for citramalate production by Issatchenkia orientalis.

Taylor-Couette reactors, with their excellent mixing capabilities, show immense potential as bioreactors, although their application in this context remains relatively unexplored. By addressing the heterogeneity commonly observed in traditional stirred-tank bioreactors, the use of Taylor-Couette reactors can contribute to improved production outcomes. Parallel fermentations using different K_La values and power inputs are conducted to compare the production of fatty alcohols between the two reactor types. In the second case study, the air feed rate emerges as a decisive factor for resource management between biomass accumulation and production in citramalate-producing Issatchenkia orientalis. Lower air feeding rates result in reduced biomass accumulation but elevated production titers, whereas higher air feed rates facilitate rapid biomass accumulation with lower production yields. Our study emphasizes the importance of exploring and optimizing fermentation conditions by manipulating air feeding rates.

In summary, this study underscores the significance of manipulating oxygen transfer in microbial fermentations, ultimately paving the way for successful scale-up and commercialization of engineered microbes.