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

Abstract

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.

Creating Value from Acidogenic Biohydrogen Fermentation Effluents: An Innovative Approach for a Circular Bioeconomy That Is Acquired via a Microbial Biorefinery-Based Framework

“…It is imperative to acquire deeper insights into these variables as they impact the dominant microbiota and VFA recovery [17]. They are usually evaluated one-at-the-time in the literature in order to ascertain their individualist roles [18,19]. Hence, the individualist impact of these variables on VFA recovery will be explained in this section.…”

“…A diagram summarizing the use of acidogenic VFAs in other bioprocesses is shown in Figure 3. Cheese whey Sludge Temp = 30 • C, pH = 5.0-6.0, FM = batch, process time = 0.5 day NA Butyric acid, propionic acid, and valeric acid [18] COD, chemical oxygen demand; FM, fermentation mode; HRT, hydraulic retention time; NA, not available/reported; OFMSW, organic fraction of municipal solid waste; OLR, organic loading rate; Temp, temperature; VS, volatile solids.…”

Effect of Fermentation Time, pH, and Their Interaction on the Production of Volatile Fatty Acids from Cassava Wastewater

“…Studies in this field typically explore the influence of operational and environmental factors on the process, such as pH, hydraulic retention time (HRT), solids retention time (SRT), temperature (T), organic loading rate (OLR), substrate to microorganism (S/M) ratio, headspace partial pressure, and inoculum [17][18][19][20]. Adequate control of these operational variables is important to ensure high yield and composition of VFA production.…”