Sunlight active TiO2-Bi2WO6 photocatalyst pretreatment of biomass for simultaneous hydrolysis and saccharification in bioethanol production

Abstract

In this work we examine photocatalysis as an alternative to the conventional enzymatic hydrolysis and liquefaction in the upstream processing of biomass for bioethanol production. A highly efficient visible light active TiO2-Bi2WO6photocatalyst having a band gap of 2.7 eV was used to deconstruct potato mash and casuarina sawdust. Thebiomass was pretreated with thephotocatalyst under sunlight for 5 h and thesawdust was subjected toprolonged treatmentsunder a 65 W fluorescent light source. Photocatalytically deconstructed biomass was subjected to fermentation by yeast. Control biomass was subjected to standard liquefaction byα amylasefollowed by yeast fermentation. Analysis of photocatalytic deconstructed products by ESI-MS reveals increasing glucose accumulation up to two hours followed by decrease upon prolonged pretreatment, suggesting possible cleavageof evolving glucose moieties. Increased concentration of lower carbonfragments in the products further corroborates this finding. HPLC analysis of fermentation products show ethanol yield on samples subjected to photocatalysis as upstream processing is comparable to that of standard enzymatic fermentation. It is thus demonstrated that visible light active photocatalysis of biomass upstream of the fermentation process can be used in place of enzymatic or chemical hydrolysis inethanol production which also constitute an environmentally benign approach.