Optimizing Sampling Strategies: Selecting Precise Sampling Times of S. cerevisiae in Octanoic Acid Production with the Cell Growth Quantifier

In this study, a Saccharomyces cerevisiae strain was genetically engineered to produce octanoic acid, a medium-chain fatty acid widely utilized as a platform chemical. This biotechnological approach represents a sustainable alternative to traditional production methods. However, further optimization is required to enhance yield.

To address this challenge, researchers aimed to deepen our understanding of the physiological changes occurring in yeast cells during octanoic acid production. To achieve this, they conducted a comparative analysis of the RNA profiles of the production strain and a non-production strain, both cultivated under identical conditions.

Of particular importance was the distinction between three distinct growth phases, as octanoic acid production was observed to occur during specific phases of growth. Leveraging the Cell Growth Quantifier (CGQ), the researchers generated a comprehensive growth profile. These high-resolution growth curves not only provided insights into cellular physiological behavior, as reflected in the growth pattern of the cells, but also facilitated the selection of precise sampling time points: early exponential phase, post-diauxic shift, and during the ethanol consumption phase when growth rate decreased.

Through a comparative analysis of growth, fatty acid composition, and gene expression profiles between the producer and a reference strain, this study unveiled profound insights into transcriptomic changes during octanoic acid production. Central to this investigation was the methodical selection of sampling time points, recognizing the distinct metabolic transitions across different growth phases intricately linked to octanoic acid production. Leveraging the CGQ, precise time points were identified based on growth dynamics, eliminating the guesswork associated with blindly sampling at estimated fermentation intervals. Additionally, comprehensive growth profiles were obtained, revealing observable metabolic events such as the diauxic shift. This enabled the authors to correlate shifts in S. cerevisiae metabolism from glucose to ethanol consumption with their observations on octanoic acid yields, further enriching their understanding of the production process.