Pretreatment of antibiotic fermentation residues by combined ultrasound and alkali for enhancing biohydrogen production

Antibiotic fermentation residues has been classified as Hazardous Waste in China since 2008, but its effective disposal and resource recovery remains a problem. Due to its high content of bioavailable organic matters, antibiotic fermentation residues can be utilized as a potential candidate for biohydrogen production. However, the complex matrix of antibiotic fermentation residues can restrict its efficiency of biohydrogen production. In this study, the effect of ultrasonic, alkaline and their combined pretreatments on the solubility of antibiotic fermentation residues was investigated to improve biohydrogen production. The results showed that the combined ultrasonic-alkaline pretreatment effectively disrupted the complex matrix of antibiotic fermentation residues and synergistically improved the biohydrogen production. Soluble chemical oxygen demand (SCOD) and soluble carbohydrate content were improved by 61.6% and 105% after the combined pretreatment, respectively. Due to the solubilization effect and the enhanced enzymatic hydrolysis, the hydrogen yield reached 17.0 mL/g-volatile solids (VS) with the combined pretreatment, which was 78.9% higher compared to the control group. The combined pretreatment also improved the hydrogen production rate and substrate utilization, and decreased the lag time. Microbial community analysis showed that the hydrogen-producing bacteria (e.g. Paraclostridium, Escherichia-Shigella and Hafnia-Obesumbacterium) were more enriched with the combined pretreatment, while hydrogen-producing competitors were inhibited, which contributed to the more efficient hydrogen fermentation. This study demonstrated the technical feasibility of using ultrasonic-alkaline pretreatment to improve the biohydrogen production from antibiotic fermentation residues. (c) 2020 Elsevier Ltd. All rights reserved.