Bioethanol Production from Switchgrass Grown on Coal Fly Ash-amended Soil

摘要

Potentially toxic concentrations of certain mineral elements may be taken up in plant biomass produced on coal fly ash (CFA) contaminated soil. This raises concerns about efficiencies of downstream processes, such as hydrolysis and fermentation involved in biomass conversions to bioethanol. A greenhouse pot experiment was conducted to assess bioethanol yield from switchgrass biomass produced on CFA-amended soil (0, 7.5 and 15 %, w/w CFA/soil). Separate aliquots of the CFA-amended soils were either inoculated with isolate of arbuscular mycorrhizal fungi (AMF), Rhizophagus clarus, or fortified with reduced glutathione (GSH). Mineral elements in the CFA-amended soils and plant tissues were determined using ICP-OES. Shoot samples of harvested biomass were subjected to microwave-assisted acid pretreatment, enzymatic hydrolysis and fermentation. The reducing sugar (glucose) and bioethanol in the biomass hydrolysate were determined by spectrophotometry. Results showed that CFA had a concentration-dependent increase on the levels of the mineral elements in soils that were amended. Subsequent uptake of the mineral elements in switchgrass tissues was modulated by CFA-soil amendment, AMF inoculation, and GSH fortification. The glucose concentrations in biomasss hyzrolysate of switchgrass grown on 7.5 and 15% CFA-amended soils were significantly higher (p < 0.05) than the unamended (control) soil without significant adverse effect on the bioethanol yield. The bioethanol concentration (μg/mg DW) in the fermented hydrolysate of switchgrass grown on 15% CFA-amended soil (26.63) was higher than the control soil (24.46). Likewise, AMF and GSH enhanced bioethanol yield from hydrolysate of switchgrass biomass grown on the CFA-amended soil. Our results indicated that coupling CFA-amended soil with either AMF or GSH can enhance bioethanol yield.