Biogas production and metabolite profiling from anaerobic biodegradation of free cyanide using municipal waste activated sludge

This study investigated the biodegradation of free cyanide (FCN) under anaerobic conditions using municipal waste activated sludge (MWAS) for subsequent biogas production and metabolite profiling in an airtight stirred tank bioreactor. The pH, temperature, and agitation speed were set at 9.5, 35 °C and 85 rpm respectively and the experiment was ran for 14 days at 100 mg FCN/L. After the biodegradation process, the metabolites were extracted using ethyl acetate and thereafter, metabolite profiling was performed using LC-QTOF-MS/MS. The microorganisms achieved an FCN biodegradation efficiency of 99.6 %, while the maximum biogas produced were 229 mL and 179 mg COD/L for captured and dissolved biogas respectively. 248 metabolites were detected and these included tert-butyl[amino(H1,2,4,-triazol-1-yl)methylidene] carbamate, 8-hydroxyquinone, 2.5-difluro-1H-imadazole-4-carboxylic acid, oleoyl ethyl amide (OEtA) and pterin; metabolites of medical significance. The findings of this study demonstrated that it is possible to produce value-added products from anaerobic cyanide treatment processes, which can be applied in various fields.