Mechanism of CaCO3 efficiently promoting hydrogen production by Clostridium butyricum BJ-10.

Aims: This study aims to explore the effect of adding CaCO3 on the hydrogen production by the fermentation of Clostridium butyricum (C. butyricum) BJ-10 and the mechanism of promoting hydrogen production by C. butyricum.

Methods and results: Determine the effect of CaCO3 on hydrogen production by C. butyricum through fermentation. When the concentration of CaCO3 was 50 mmol·L-1, the cumulative hydrogen production was 3726.27 mL·L-1, which was 193% higher than that of the control group. By exploring the effects of adding CaCl2, Na2CO3, and pH control on the hydrogen production of C. butyricum, it was found that the main reason why CaCO3 promoted the hydrogen production of C. butyricum was that it could control the pH of the fermentation broth within a suitable range. Transcriptomic analyses were performed on C. butyricum with and without the addition of CaCO3, respectively. After the addition of CaCO3, a total of 222 genes were significantly expressed, of which 141 genes were significantly upregulated and 81 genes were significantly downregulated. Among them, genes related to carbohydrate metabolism were upregulated (pgm by 1.95-fold, eno by 2.33-fold, and pflD by 3.43-fold).

Conclusions: CaCO3 can accelerate the process of glycolysis by upregulating the pgm and eno genes, and further promote the increase in hydrogen production by upregulating the pflD gene. This study can provide a reference for the development of biological hydrogen production technology.