The effects of co-supplemented Fe, Co and Ni on Fe bioavailability and microbial community structure in mesophilic food waste anaerobic digestion by using response surface methodology

Optimized doses and dosing strategies for trace element application in the anaerobic digestion (AD) process still face challenges. In this study, the response surface methodology (RSM) of Box-Behnken was used to investigate the effects of Fe, Co and Ni co-supplementation dosages on the mesophilic AD process of food waste (FW). According to RSM results, the maximum experimental methane yield of 677.9 mL/g VS was obtained under the optimal condition (Fe: 113.1, Co: 0.51, and Ni: 2.44 mg/L), representing a 27.4 % increase compared to the control group without trace element addition. The noticeable decrease in Fe bioavailability in control group indicates a higher demand for Fe during AD of FW. However, while increasing the Fe dose did not enhance its easily bioavailable fraction, that of Co and Ni exhibited a negative effect on Fe bioavailability. In the optimal condition, the syntrophic methanogenesis between syntrophic genera and obligate hydrogenotrophic methanogens improved, along with the increased relative abundance of ATP-binding cassette transporter and two-component systems, which correlated with enhanced Fe bioavailability. These findings provide deeper insights into the interactions of co-supplemented trace elements during AD of FW. [Display omitted]