Impact of pH , temperature, and hydraulic residence time on the acidogenic fermentation of fruit and vegetable waste and microbial community analysis

BACKGROUND The carboxylic acids produced through acidogenic fermentation of fruit and vegetable waste present wide application and high added value. By performing batch experiments, the influence of pH and temperature on the acidogenic fermentation performance was investigated, and the effects of hydraulic retention time (HRT) on performance and microbial community in semi‐continuous fermentation were also studied. RESULTS A maximum product yield of 0.66 ± 0.01 g g −1 VS fed (volatile solids of feed substrate) was found at mesophilic temperature and pH 9.0; acetic acid, propionic acid, and butyric acid comprised 59%, 20%, and 21% of the product, respectively. During semi‐continuous fermentation, a maximum product yield of 0.69 ± 0.03 g g −1 VS fed was found at pH 9.0 and an HRT of 5 days. Lactic acid and acetic acid were regarded as the main products, with respective percentages of 85% and 12%. Reducing the HRT to 3 days increased the daily production from 11.33 ± 0.46 to 15.89 ± 0.67 g d −1 . Microbial community analysis revealed that Lactobacillus was predominant in the semi‐continuous alkaline fermentation system. CONCLUSION Alkaline fermentation was more favorable for obtaining higher product yield both in batch and semi‐continuous fermentation. Within semi‐continuous alkaline fermentation, the maximum yield was observed at an HRT of 5 days, but a higher daily production was found at an HRT of 3 days. Additionally, reducing the HRT did not change the dominant bacteria but could change the composition of the products. This work provides a theoretical basis and guidance for enhancing product yield and optimizing formation of product.