A. Shende, M. Hussein, R. Bhosale, D. Harder-Heinz, R.V. Shende
South Dakota School of Mines & Technology, US
photocatalysis, microbial degradation, Kraft lignin, valuable products
Kraft lignin (KL), a waste product of paper and pulp industry is recalcitrant to biochemical degradation. In our attempt to overcome KL recalcitrance, we coupled photoreforming of Kraft lignin (KL) with microbial degradation. It is anticipated that the TiO2 mediated photocatalytic pretreatment of KL would induce depolymerization of the KL chains and cleavage of aromatic rings to form products amenable to microbial degradation. One of the drawbacks in using TiO2 based photocatalyst is its excitation in UV range. To increase response to visible light, Pt/TiO2 nanomaterial was doped with ZnO and ZrO2. This novel nanocomposite was synthesized by sol-gel process with Pluronic P123 surfactant. It was characterized by BET surface area analyzer, XRD, TEM and SEM. Suspension of KL and photocatalyst was irradiated with light of 100 mW/cm2 power density emitted by a solar simulator fitted with AM1.5G. Photodegradation of KL was monitored by UV-differential spectroscopy and size exclusion chromatography. Parameters such as irradiation time and catalyst loading were optimized for maximum KL degradation. Photodegraded KL was used as a substrate for lignin degrading facultative anaerobes enriched from soil collected under decomposing wood. Degradation products of phototreated KL and untreated KL were analyzed by GC-MS and compared.