Effect of beryllium (Be), chromium (Cr), arsenic (As), and thallium (Tl) on cells growth and production of acetic and butyric acid by Clostridium butyricum

This is the authors' abstract. We don't add key points for this paper.

Clostridium butyricum is a resilient bacterium capable of surviving in extreme conditions such as soil, healthy human feces, and the intestinal tract. It ferments organic acids efficiently, producing metabolic by-products such as CO2, H2, acetic, and butyric acids. The present study investigated the impact of arsenic (As), beryllium (Be), chromium (Cr), and thallium (Tl) on the growth and metabolism of C. butyricum where they produced acetic and butyric acids. Batch fermentation was conducted using nitrogen gas in synthetic media containing these metals at pH 6.5 and 37 °C under anaerobic conditions. Metal concentrations were modeled using leachate to simulate environmental exposure. At 0.10 ppm, chromium enhanced C. butyricum growth, with a growth rate of 78.76%, accompanied by acetic acid productivity of 0.48 g/L/h, and butyric acid production of 0.02 g/L/h. In contrast, the growth of C. butyricum was inhibited by beryllium at 42.97% and thallium at 22.12%, respectively. Arsenic exhibited dual behavior, acting as a promoter or inhibitor of the fermentation of C. butyricum where chromium supported bacterial growth. The substrate contained beryllium, so acetic acid productivity was 0.05 g/L/h, and butyric acid was 0.18 g/L/h. Then, the rate of acetic and butyric acids was 0.09 g/L/h, while thallium was 0.14 g/L/h. These findings demonstrate that heavy metals significantly impact bacterial growth and acid production.