Conversion of Renewable Biogas into Single-Cell Protein Using a Combined Microalga- and Methane-Oxidizing Bacterial System

Abstract

The high-value utilization of biogas and reasonable disposal of biogas slurry have become an issue worldwide. In the current study, the possibility of single-cell protein (SCP) recovery from biogas and sterilized biogas slurry using a combined microalga (MG)- (Chlorella vulgaris) and methane-oxidizing bacterial (MOB) system was investigated. Results showed that the optimum content of sterilized biogas slurry for MG cultivation was 80% (v/v), while it was 40% (v/v) for MOB. Thus, the biogas slurry content for the combined system was selected as 40% (v/v), under which condition the dry biomass and SCP yields were 280 and 90.43 mg/L, respectively. The SCP yield of MOB solely decreased by 9.57% when the Na2S concentration increased from 2.19 to 12.53 mg/L, while the SCP yield of the combined system was not obviously affected. Besides, the amino acid profiles of MG and MOB were altered by Na2S, while it was more balanced in the combined system.