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

In this work we examine photocatalysis as an alternative to the conventional enzymatic hydrolysis and lique-faction in the upstream processing of biomass for bioethanol production. A highly efficient visible light active TiO2-Bi2WO6 photocatalyst having a band gap of 2.7 eV was used to deconstruct potato mash and casuarina sawdust. The biomass was pretreated with the photocatalyst under sunlight for 5 h and the sawdust was sub-jected to prolonged treatments under a 65 W fluorescent light source. Photocatalytically deconstructed biomass was subjected to fermentation by yeast. Control biomass was subjected to standard liquefaction by alpha amylase -followed 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 cleavage of evolving glucose moieties. Increased concentration of lower carbon fragments 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 in ethanol production which also constitute an environmentally benign approach.

Automated summary

This study explores photocatalysis as an alternative method for upstream processing in bioethanol production. By using a highly efficient visible light active TiO2-Bi2WO6 photocatalyst to deconstruct potato mash and casuarina sawdust, and subjecting the deconstructed biomass to fermentation by yeast, it was found that the ethanol yield from photocatalytically deconstructed biomass is comparable to that of biomass processed by standard enzymatic hydrolysis.