36 / 2023-04-29 23:36:50

Responses of fermentative pathway to the ratio of inoculum to substrate during the anaerobic treatment of main carbon sources in the food wastes

Anaerobic fermentation,Food wastes,ISR,Short chain organic acids,Fermentative pathway

High value utilization of food wastes (FW) via short chain organic acids (SCOAs) fermentation is deemed to be more effective than that via anaerobic digestion to produce biogas. However, the performance of SCOAs production is always affected by initial conditions, among which substrate to inoculum ratio (ISR) is a crucial one. In this study, cooked rice (Rice), blanched vegetable (Veg) and chicken breast (Bre) were employed as three model complexes of representative components in the food waste to investigate the effects mechanism of ISR (1:2, 1:1 and 2:1) on the SCOAs production. Wherein, Rice acted as the starch-rich components, Veg as cellulose-rich components and Bre as protein-rich components, respectively, and they were fermented individually. The results indicated that the larger the ISR is, the higher the yield of SCOAs displays. Besides, the duration of acidification is remarkably affected by the substrate type rather than ISR. According to the component distribution of SCOAs, the fermentative pathway is significantly affected by the ISR and the substrate type. It is noting that there may be a process of carbon chain elongation from lactic acid to butyric acid along with the fermentative pathway transformation. For the Rice, lactic acid-type fermentation is predominant whereas substituted by the butyric acid-type acid type ultimately at higher ISR. Veg fermentation belonged to acetic acid and lactic acid mixed-type before the first two days and transformed into acetic acid-type dominantly. Due to the complex structure of protein, the fermentative pathway of Bre is the mixed type and scarcely affected by the ISR. The acetate (42.52% to 88.45%), propionate (5.26% to 22.70%) and isovalerate (3.96% to 22.59%) are main components of SCOAs produced from Bre and no lactic acid is generated. The results above may provide references for the process optimization of directed fermentation for individual acid when treating different main compositions of FW.