TERMITE’S BIOMASS DEGRADATION STRATEGY AND BIOMIMIC TREATMENT

Shuai Zhang

Termite, C. formosanus, is well known for its efficient wood digestion ability. The purpose of this dissertation reesasrch is to firstly investigate the related mechanism used by termite in wood digestion and then develop the bio-mimic process for treating the different components of lignocellulosic biomass. In the first part of the study, we proved the hydroquinone-production route in termite by expression of β-glucosidases (Glu1B) in E.coli Rosetta and further hydrolysis arbutin for hydroquinone generation. Arbutin was found as a compound existing in southern pine extractives with the concentration of 0.08 mg/g and the enzyme activity of Glu1B to arbutin was shown as 0.034 IU/ml at 28 oC. This suggested a pathway for HO· production in termite: arbutin in wood particles is initially hydrolyzed by β-glucosidases to release hydroquinone, which is further catalyzed by iron and lignin oxidase for HO· generation. With this knowledge, we developed an electro-Fenton process to mimic termite’s strategy in the second part of the study. In the electro-Fenton process, we used electricity for electron supply to oxygen through cathode reduction. This simulated H2O2 conversion process, in which oxygen extracted electrons from hydroquinone. Then, the generated H2O2 was further decomposed by iron for HO· production. In the next step, we used electro-Fenton process in lignin treatment. It was discovered that electro-Fenton process was able to transform lignin to long-chain fatty acids. The possible mechanism was that lignin was initially oxidized to volatile fatty acids (VFAs) and then, the VFAs were synthesized to long-chain fatty acids through Kolbe reaction. After process optimization, the yield of long-chain fatty acids reached to 8.68 mg/L palmic acid and 8.56 mg/L octadecanoic acid. In the last part of the study, we applied electro-Fenton process to cellulose degradation. It was found that it could effectively destroy microalgae cell and degrade cellulose, the major component in microalgae cell wall. Under optimal conditions, electro-Fenton process enhanced lipid extraction from 40 to 87.53% (wt/wt, total lipid). Also, the waste water generated from electrolysis could be used for microalgae cultivation without inhibitory effect.

TERMITE’S BIOMASS DEGRADATION STRATEGY AND BIOMIMIC TREATMENT

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