a clear trendp < 0.01
Differences indicated by a p value < 0.05 were considered to suggest a clear trend, whereas p < 0.01 and p < 0.001 denoted significant and very significant differences, respectively.
Differences indicated by a p value < 0.05 were considered to suggest a clear trend, whereas p < 0.01 and p < 0.001 denoted significant and very significant differences, respectively.
The Coulomb efficiency is calculated on a 4-h interval for the fermentation process, which, for the experimental group, showed a trend of first increasing and then decreasing (Fig. 5 ).