Vibrio natriegens is sensitive to its acidic fermentation products

Vibrio natriegens is an emerging bacterial platform for a range of biotechnological applications due to its rapid growth and ease of genetic manipulation. Whereas much has been learned about V. natriegens' aerobic physiology, comparatively little is known about its anaerobic fermentative physiology, despite its relevance to many industrial conditions. We compared the metabolic parameters of V. natriegens versus another biotechnologically relevant bacterium, Escherichia coli, under fermentative conditions. Both species excreted a similar array of fermentation products, but V. natriegens consumed less glucose and had a lower product titer. V. natriegens also exhibited rapid death, reaching extinction within 12 h after the growth phase, 3 days sooner than E. coli. Rapid V. natriegens death was avoided, and glucose consumption and product titers improved, by increasing the buffering capacity of the growth medium, indicating that V. natriegens is comparatively sensitive to its organic acid fermentation products. Aside from a minor role for RpoS in acid resistance, the V. natriegens genome lacks nearly all the acid resistance genes that have been characterized in E. coli and Vibrio cholerae. Our findings thus highlight an acid sensitivity that will need to be considered when designing fermentative applications of V. natriegens.

Bioprocessing, the biological conversion of renewable resources into value-added chemicals, is poised to meet an increasing demand for sustainable alternatives to petroleum-based products. Many examples of bioprocessing feature anoxic fermentations that naturally maximize product formation relative to growth of the microbial catalyst. Vibrio natriegens is a facultatively fermentative bacterium that has gained attention for bioprocessing due to its rapid growth rate and ease of genetic engineering. However, the fermentative properties of V. natriegens have not been compared to traditional bioprocessing workhorses like Escherichia coli. We revealed that V. natriegens is comparatively sensitive to its own acidic fermentation products, likely because V. natriegens lacks acid resistance mechanisms possessed by E. coli. Thus, fermentative applications must address this sensitivity either by buffering the fermentations, engineering resistance mechanisms, or bypassing the sensitivity by engineering V. natriegens to produce neutral products.